Co-reporter:Yangxia Han, Yonglei Chen, Jie Feng, Juanjuan Liu, Sudai Ma, and Xingguo Chen
Analytical Chemistry 2017 Volume 89(Issue 5) pp:
Publication Date(Web):February 10, 2017
DOI:10.1021/acs.analchem.6b04509
Because 2,4,6-trinitrophenol (TNP) and its analogues such as 2,4,6-trinitrotoluene (TNT) possess similar chemical structures and properties, the reliable and accurate detection of TNP from its analogues still remains a challenging task. In the present work, a selective and sensitive method based on the water-soluble silicon nanoparticles (SiNPs) for the determination of TNP was established. The SiNPs with good thermostability and excellent antiphotobleaching capability were prepared via a simple one-pot method. Compared with the synthesized time of other nanomaterials with respect to the detection of TNP, this method avoided a multistep and time-consuming synthesis procedure. Significantly, the fluorescence of the SiNPs could be remarkably quenched by TNP via an inner filter effect. A wide linear range was obtained from 0.02 to 120 μg/mL with a limit of detection of 6.7 ng/mL. The method displayed excellent selectivity toward TNP over other nitroaromatic explosives. The proposed fluorescent method was successfully applied to the analysis of TNP. Moreover, a straightforward and convenient fluorescent filter paper sensor was developed for the detection of TNP, providing a valuable platform for TNP sensing in public safety and security.
Co-reporter:Hongxia Dai, Wenjuan Lü, Xianwei Zuo, Qian Zhu, Congjie Pan, Xiaoying Niu, Juanjuan Liu, HongLi Chen, Xingguo Chen
Biosensors and Bioelectronics 2017 Volume 95(Volume 95) pp:
Publication Date(Web):15 September 2017
DOI:10.1016/j.bios.2017.04.021
•Hierarchically porous MIL-100(Cr)-B was used for the immobilization of HRP.•The biosensor is durable for high sensitive and selective detection of H2O2.•The biosensor has been successfully used to the real-time detection of H2O2 released from living cells.In this work, we report a durable and sensitive H2O2 biosensor based on boronic acid functionalized metal-organic frameworks (denoted as MIL-100(Cr)-B) as an efficient immobilization matrix of horseradish peroxidase (HRP). MIL-100(Cr)-B features a hierarchical porous structure, extremely high surface area, and sufficient recognition sites, which can significantly increase HRP loading and prevent them from leakage and deactivation. The H2O2 biosensor can be easily achieved without any complex processing. Meanwhile, the immobilized HRP exhibited enhanced stability and remarkable catalytic activity towards H2O2 reduction. Under optimal conditions, the biosensor showed a fast response time (less than 4 s) to H2O2 in a wide linear range of 0.5–3000 μM with a low detection limit of 0.1 μM, as well as good anti-interference ability and long-term storage stability. These excellent performances substantially enable the proposed biosensor to be used for the real-time detection of H2O2 released from living cells with satisfactory results, thus showing the potential application in the study of H2O2-involved dynamic pathological and physiological process.
Co-reporter:Congjie Pan, Wenjuan Lv, Guoxiu Wang, Xiaoying Niu, Heying Guo, Xingguo Chen
Journal of Chromatography A 2017 Volume 1484(Volume 1484) pp:
Publication Date(Web):10 February 2017
DOI:10.1016/j.chroma.2017.01.017
•Simultaneous separation of two target fractions was achieved by one-dimensional CEC.•Six cationic analytes and four neutral analytes were separated in a single run.•The method was applied to separation and detection of tested analytes in urine.Developing simple methods for separation of analytes that belong to different classes is of great importance. Herein, we developed a simple one-dimensional (1-D) capillary electrochromatography method to demonstrate the simultaneous separation of target fractions that belong to two different classes (i.e., cationic and neutral analytes) without switching buffer solution by a zeolitic imidazolate framework ZIF-8 coated capillary column. Owing to the difference of charge-to-mass ratio of the cationic analytes, the interaction of the cationic analytes and coating material ZIF-8 and the hydrophobic interactions between the neutral analytes and the microporous framework of ZIF-8, six cationic analytes and four neutral analytes were simultaneously separated in a single run by 1-D capillary electrochromatography. The relative standard deviations (RSDs) of the analytes migration time for intra-day, inter-day and column-to-column were in the range of 0.11–0.87%, 0.54–2.04% and 2.00–6.89% and the RSDs of the analytes peak area for intra-day, inter-day and column-to-column were in the range of 0.70–4.45%, 1.33–6.20% and 2.27–11.88%. Additionally, the developed method was employed in the analysis of urine samples with satisfactory recoveries.
Co-reporter:Huige Zhang;Liang Peng;Maoxing Li;Ji Ma;Shengda Qi;Hongli Chen;Lei Zhou;Xingguo Chen
Analyst (1876-Present) 2017 vol. 142(Issue 13) pp:2419-2425
Publication Date(Web):2017/06/26
DOI:10.1039/C7AN00541E
Sensitive detection of a low abundant protein is essential for biomedical research and clinical diagnostics. Herein, we develop a label-free colorimetric biosensor for the sensitive detection of recombinant human vascular endothelial growth factor-165 (VEGF165). This biosensor consists of an aptamer-based hairpin probe, an assistant DNA–trigger duplex and a linear template. In the presence of VEGF165, the specific binding of VEGF165 with the aptamer-based hairpin probe results in the opening of a hairpin probe and the opened hairpin probe subsequently hybridizes with the single-stranded region of the assistant DNA–trigger duplex to initiate the strand displacement amplification (SDA) to yield abundant triggers. The released triggers can further function as the primers to anneal with the hairpin probe and lead to the opening of the hairpin structure, which subsequently hybridizes with the assistant DNA–trigger duplex to initiate the next round of SDA reaction and generates more triggers. Large amounts of triggers could be generated by the synergistic operation of dual SDA reaction, and the obtained triggers can initiate a new round of SDA reaction to yield numerous G-quadruplex DNAzymes, which subsequently catalyze the conversion of ABTS2− to ABTS˙− by H2O2 to yield a color change with the assistance of a cofactor hemin. In contrast, in the absence of target VEGF165, the hairpin probe, the assistant DNA–trigger duplex and the linear template can stably coexist in solution, and thus no color change is observed because no trigger can initiate SDA to generate the G-quadruplex DNAzyme. This biosensor has a low detection limit of 1.70 pM and a dynamic range over 3 orders of magnitude from 24.00 pM to 11.25 nM. Moreover, the biosensor shows excellent specificity toward the target VEGF165 and the entire reaction can be carried out in an isothermal manner without the involvement of a high precision thermal cycler, making the current assay extremely cost effective.
Co-reporter:Su-dai Ma, Yong-lei Chen, Jie Feng, Juan-juan Liu, Xian-wei Zuo, and Xing-guo Chen
Analytical Chemistry 2016 Volume 88(Issue 21) pp:10474
Publication Date(Web):September 30, 2016
DOI:10.1021/acs.analchem.6b02448
A sensitive and selective fluorescence “turn-off” sensor to detect heparin using water-soluble silicon nanoparticles (Si NPs) was developed for the first time. The Si NPs were synthesized by a simple one-step procedure, which did not need high-temperature and complex modification. The as-prepared Si NPs featured strong fluorescence, favorable biocompatibility, and robust photo- and pH stability. Significantly, the Si NPs were induced to assemble or aggregate via hydrogen bonding, which resulted in the fluorescence of Si NPs quenched. Under the optimized conditions, the linear range was obtained from 0.02 to 2.0 μg/mL, with a limit of detection of 18 ng/mL (equal to 0.004 U/mL). It was lower than the proper therapeutic level of heparin during cardiovascular surgery and long-term therapy. This proposed method was relatively free of interference from heparin analogues, which commonly existed in heparin samples and could possibly affect heparin detection. Moreover, it did not need to introduce any control medium. As expected, the method was successfully applied to detect heparin in human serum samples with satisfactory recovery ranging from 98.8 to 102.5%. The Si NPs were superbly suitable for cell imaging owing to the negligible cytotoxicity and excellent biocompatibility.
Co-reporter:Jie Feng, Yonglei Chen, Yangxia Han, Juanjuan Liu, Cuiling Ren, Xingguo Chen
Analytica Chimica Acta 2016 Volume 926() pp:107-117
Publication Date(Web):5 July 2016
DOI:10.1016/j.aca.2016.04.039
•A one-pot and low-temperature synthetic method for the fluorescent CNPs.•Synthesis mechanism of the CNPs.•A “turn-off” fluorescence sensor for fast, sensitive, and selective detection of Fe3+.•The synergistic action of the inner filter effect and static quenching mechanism.In recent years, extensive researches are focused on the fluorescent carbon nanoparticles (CNPs) due to their excellent photochemical, biocompatible and water-soluble properties. However, these synthesis methods are generally suffered from tedious processes. In this paper, fluorescent carbon nanoparticles are synthesized by a facile, one-pot, low-temperature method with trypsin and dopamine as precursors. The synthesis process avoids any heating operation and organic solvent, which provides a “green” and effective preparation route. The obtained CNPs exhibit excellent water-solubility, salt-tolerance and photostability. Based on the synergistic action of the inner filter effect and static quenching mechanism, the CNPs are exploited as a “turn-off” fluorescence sensor for sensitive and selective detection of Fe3+ ions. The probe shows a wide linear range from 0.1 to 500 μM, with a limit of detection of 30 nM. Furthermore, the as-fabricated fluorescent sensing system is successfully applied to the analysis of Fe3+ in biological samples such as human urine and serum samples with satisfactory recoveries (92.8–113.3%).
Co-reporter:Xiaoying Niu, Sanyuan Ding, Weifeng Wang, Yali Xu, Yinyin Xu, Hongli Chen, Xingguo Chen
Journal of Chromatography A 2016 Volume 1436() pp:109-117
Publication Date(Web):4 March 2016
DOI:10.1016/j.chroma.2016.01.066
•The COF-LZU1 was utilized as stationary phase in OT-CEC for the first time.•Baseline separation of the model analytes was achieved by the coated capillary.•The novel coated capillary had the capacity of successive 300 runs at least.Covalent organic frameworks (COFs) have attracted much attention because of their permanent nanoscale porosity and higher surface area compared to zeolites as well as robustness. COFs have great potential in several fields such as hydrogen storage, gas separation, and catalysis. However, COFs have not yet been applied in capillary electrochromatography. Herein, covalent organic frameworks-LZU1 (COF-LZU1) was used as the stationary phase in open-tubular capillary electrochromatography for the first time. Compared to the monoliths used in electrochromatography, the preparation technique of a COF-LZU1-coated capillary was simple and practical. The baseline separation of model analytes including alkylbenzenes, polyaromatic hydrocarbons, and anilines by the COF-LZU1-coated capillary was achieved based on the size selectivity of COF-LZU1 porous structure and hydrophobic interactions between the model analytes and organic ligands of COF-LZU1. The load capacity of the COF-LZU1-coated capillary for naphthalene was 0.6 mg/mL. For three consecutive runs, the intraday relative standard deviations (RSDs) were 1.4–2.6% for the migration time and 2.7–8.7% for the peak area. The interday RSDs were 1.3–3.9% for the migration time and 3.7–9.7% for the peak area. The column-to-column reproducibility of migration time was in the range 1.0–3.9%. Moreover, the coated capillary was used for >300 runs with no changes in the separation efficiency. Thus, COFs have great potential in capillary electrochromatography and may provide a new method for chromatographic separation.
Co-reporter:Congjie Pan, Weifeng Wang, Xingguo Chen
Journal of Chromatography A 2016 Volume 1427() pp:125-133
Publication Date(Web):4 January 2016
DOI:10.1016/j.chroma.2015.12.020
•A novel homochiral metal organic framework coated capillary column was developed.•The coating was in situ synthesized in 1 h by using ZnO as nucleating agents.•Well enantioseparation of three monoamine neurotransmitters was achieved.•The isomers of nitrophenols and analogues of bisphenols were also well separated.Fabricating metal-organic frameworks (MOFs) with the use of nucleating agents in the microenvironment have attracted increasing attention recently. Herein, a simple and rapid synthesis method was developed to in situ fabricate homochiral MOF [Zn(s-nip)2]n in the capillary inner wall by using ZnO nanoparticles as efficient nucleating agents for open tubular capillary electrochromatography (OT-CEC) separation of monoamine neurotransmitters enantiomers of epinephrine, isoprenaline and synephrine, the diastereoisomers of ephedrine and pseudoephedrine, the isomers of nitrophenols and analogues of bisphenols with good resolution. The relative standard deviations (RSDs) for the analytes migration time of intra-day, inter-day and column-to-column were in the range of 0.8–2.1% (n = 10), 0.3–3.2% (n = 3) and 3.2–9.3% (n = 3), respectively. Additionally, the homochiral MOF [Zn(s-nip)2]n coated capillary column could be successively used over 260 runs without observable change in the separation efficiency.
Co-reporter:Wei-feng Wang, Fu-rong Ju, Yan-li Ran, Hui-ge Zhang and Xing-guo Chen
Analyst 2016 vol. 141(Issue 3) pp:956-962
Publication Date(Web):26 Nov 2015
DOI:10.1039/C5AN01642H
Ischemic stroke is caused when blood flow to the brain is stopped and is a major cause of death and long term disability across the globe. Excessive release of neurotransmitters is triggered in the brain by ischemia that mediates neuronal damage and causes ischemic injury. In this study, a simple, sensitive, and on-line preconcentration capillary electrophoresis method based on electrokinetic supercharging (EKS) was developed for the determination of the biogenic amines including dopamine (DA), epinephrine (E), and norepinephrine (NE) in C57BL/6 mice brain. Under the optimized conditions, the analytes were concentrated and detected within 10 min. The detection limits for the analytes ranged from 0.42 to 0.57 ng mL−1 for a mice brain matrix. With the proposed method, the analyses of three neurochemical amines in C57BL/6 mice brain tissue during cerebral ischemic/reperfusion had been performed successfully.
Co-reporter:Juanjuan Liu, Yonglei Chen, Weifeng Wang, Jie Feng, Meijuan Liang, Sudai Ma, and Xingguo Chen
Journal of Agricultural and Food Chemistry 2016 Volume 64(Issue 1) pp:371-380
Publication Date(Web):December 11, 2015
DOI:10.1021/acs.jafc.5b05726
This work describes a “switch-on” fluorescence approach for sensing of ascorbic acid (AA) in food samples. In the present method, the fluorescence intensity (FL) of carbon quantum dots (CQDs) was first quenched by addition of MnO2 nanosheets through an inner filter effect to form a CQDs-MnO2 probe. When reductive AA was introduced into the quenched CQDs solution, the added MnO2 was destroyed due to the redox reaction between AA and MnO2 nanosheets, and the FL of the system was recovered. Under the optimal conditions, the limit of detection for AA was 42 nM, with a wide concentration linear range of 0.18–90 μM. Furthermore, the as-fabricated fluorescent sensing system was successfully applied to the analysis of AA in fresh fruits, vegetables, and commercial fruit juices samples with satisfactory results.
Co-reporter:Qian Zhu, Di Dong, Xuejing Zheng, Huiqing Song, Xinrui Zhao, Hongli Chen and Xingguo Chen
RSC Advances 2016 vol. 6(Issue 30) pp:25047-25055
Publication Date(Web):01 Mar 2016
DOI:10.1039/C5RA27636E
In this work, composites with different amounts of graphene oxide (GO) and the copper-based metal–organic frameworks (HKUST-1) were synthesized. They have been applied in chemiluminescence (CL) as catalysts using the luminol–H2O2 system as a CL model for the first time. The results showed that the well-dispersed GO@HKUST-1 (GMs) greatly improved the CL intensity of the luminol–H2O2 system, up to 359-fold. Based on ascorbic acid (AA) inhibiting the CL of the luminol–H2O2–GMs system, a flow injection CL method for monitoring AA was developed. Under the optimized conditions, a good linear relationship was obtained from 0.001 μM to 10 μM, and the detection limit was 0.35 nM. Moreover, the method was successfully used to detect AA in commercial food and fruit juices with satisfactory results. Due to their fascinating features, the GMs would offer a suitable catalytic platform for CL systems and provide potential promise for the construction of CL sensors.
Co-reporter:Xin-rui Zhao, Yong-lei Chen, Lang Wang, Wei-feng Wang and Xing-guo Chen
Analytical Methods 2016 vol. 8(Issue 2) pp:393-400
Publication Date(Web):02 Dec 2015
DOI:10.1039/C5AY02405F
In this study, a simple, sensitive, and selective fluorometric platform has been constructed for measuring trypsin in biological samples using the prepared Au–peptide–FITC beacon. The fluorescence of FITC was quenched by Au NPs owing to the FRET mechanism and recovered after selective cleavage of the beacon peptide by trypsin. The calibration plot for trypsin was achieved over the concentration range of 10–100 nmol L−1 with a correlation coefficient of 0.995 and a limit of detection of 5 nmol L−1. In addition, the application of the present approach in determining the trypsin content in blood plasma samples was demonstrated to be satisfactory, which suggested its potential for diagnostic purpose.
Co-reporter:Xianwei Zuo, Huige Zhang, Qian Zhu, Weifeng Wang, Jie Feng, Xingguo Chen
Biosensors and Bioelectronics 2016 Volume 85() pp:464-470
Publication Date(Web):15 November 2016
DOI:10.1016/j.bios.2016.05.044
•WS2 nanosheet was demonstrated to develop a dual-color fluorescent biosensing platform for detection of Hg2+ and Ag+.•Without using any masking agents, the biosensor could achieve simultaneous detection of Hg2+ and Ag+ with a low detection limit.•The homogeneous assay format made this method simple and convenient.In this work, an effective dual-color fluorescent biosensing platform based on WS2 nanosheets was developed for homogeneous detection of Hg2+ and Ag+. This sensing platform was constituted by exploiting the fluorescence quenching ability of WS2 nanosheets and the interactions between WS2 nanosheets and DNA molecules. In the absence of additional any masking agents, the biosensor could achieve detection of Hg2+ and Ag+ in the same solution by monitoring fluorescence intensity changes at 525 nm and 583 nm, respectively. Hg2+ and Ag+ were selectively detected in the concentration range from 6.0–650.0 nM and 5.0–1000.0 nM, respectively, with the detection limit of 3.3 nM and 1.2 nM, respectively. It was also demonstrated that the WS2 nanosheet-based sensing platform was suitable for the simultaneous detection of Hg2+ and Ag+ in drinking water, serum and cell lysate samples. Moreover, the possible mechanism of fluorescence quenching by WS2 nanosheets was revealed to be related to static quenching, dynamic quenching, and Fo¨rster resonant energy transfer (FRET). This work extended the application of WS2 nanosheets to environmental monitoring and medical diagnosis.
Co-reporter:Hui-qing Song, Qian Zhu, Xue-jing Zheng and Xing-guo Chen
Journal of Materials Chemistry A 2015 vol. 3(Issue 19) pp:10368-10377
Publication Date(Web):01 Apr 2015
DOI:10.1039/C5TA00280J
In this paper, a simple one-pot hydrothermal procedure to create three-dimensional (3D) graphene/multiwalled carbon nanotubes/Pd (G/MWCNTs/Pd) composite hydrogels with a unique porous nanostructure was reported. During the formation of the G/MWCNTs/Pd composites, 2D graphene sheets and 1D MWCNTs were self-assembled to form interconnected porous microstructures and ultrafine Pd NPs were in situ grown on the 3D carbon-based skeleton simultaneously. In the as-obtained nanocomposites, MWCNTs not only prevented the close restacking of graphene sheets to increase the specific surface area but also provided an additional transport path to the catalyst surfaces which facilitated reactant transport. The G/MWCNTs/Pd composites proved to be an efficient, recyclable, and robust catalyst for the Suzuki cross-coupling reactions under mild aerobic conditions, which was attributed to the 3D macroporous framework with high specific surface area, numerous activation sites, and efficient transport pathways for improving the catalytic performance. Moreover, catalyst separation could be easily achieved by simple filtration, and the catalyst could be reused for at least six runs without significant loss in catalytic activity. Additionally, nearly no Pd species was released from the G/MWCNTs/Pd composites during the catalytic reactions, showing the heterogeneity in the present catalysis system.
Co-reporter:Jie Feng, Yuyun Ju, Juanjuan Liu, Huige Zhang, Xingguo Chen
Analytica Chimica Acta 2015 Volume 854() pp:153-160
Publication Date(Web):7 January 2015
DOI:10.1016/j.aca.2014.11.024
•A new method for synthesis of the BPEI-CuNCs is established.•A facile approach for Fe3+ ion sensing by fluorescence quenching is developed.•The method for Fe3+ sensing has high sensitivity and excellent selectivity.In this report we reported a facile one-pot method for synthesis of water-soluble and stable fluorescent CuNCs at room temperature, in which branched polyethyleneimine (BPEI) served as capping scaffold and ascorbic acid as reducing agent. The prepared BPEI-CuNCs exhibited excellent properties such as good water-solubility, photostability and high stability toward high ionic strength. Based on the electron transfer induced fluorescence quenching mechanism, this fluorescence probe was used for the sensitive and selective determination of ferric ions (Fe3+) in aqueous solution. The limit of detection was 340 nM in the linear range of 0.5–1000 μM, which was lower than the maximum level of Fe3+ permitted in drinking water by the U.S. Environmental Protection Agency. The method was successfully applied to the detection of Fe3+ in tap water, Yellow River water and human urine samples with the quantitative spike recoveries ranging from 95.3% to 112.0%.
Co-reporter:Congjie Pan, Weifeng Wang, Huige Zhang, Laifang Xu, Xingguo Chen
Journal of Chromatography A 2015 Volume 1388() pp:207-216
Publication Date(Web):3 April 2015
DOI:10.1016/j.chroma.2015.02.034
•A novel homochiral metal organic framework coated capillary column was developed.•The coating was in situ synthesized by a layer-by-layer self-assembly approach.•Well enantioseparation of monoamine neurotransmitters and amine drugs was achieved.Homochiral metal–organic frameworks (MOFs) are promising as porous stationary phase for open-tubular capillary electrochromatography (OT-CEC) enantioseparation owing to their fine-tuned pore sizes and large surface areas. In this work, the homochiral MOF AlaZnCl was successfully coated on the inner wall of fused silica capillary by an in situ, layer-by-layer self-assembly approach at room temperature. The results of scanning electron microscopy (SEM), X-ray diffraction (XRD), streaming potential (SP) and Fourier-transform infrared spectroscopy (FT-IR) indicated that the homochiral MOF AlaZnCl was successfully coated on the capillary inner wall. To evaluate the performance of the homochiral MOF AlaZnCl coated capillary column, the enantioseparation was carried out by using six amine drugs and monoamine neurotransmitters as model analytes and excellent enantioseparation efficiency was achieved. Run-to-run, day-to-day, and column-to-column relative standard deviations (RSDs) were all less than 5%. Moreover, the separation efficiency of the homochiral MOF AlaZnCl coated capillary column did not decrease obviously over 100 runs.
Co-reporter:Wei-feng Wang, Hui-ge Zhang, Sheng-da Qi, Hong-li Chen and Xing-guo Chen
Analyst 2015 vol. 140(Issue 12) pp:4253-4259
Publication Date(Web):30 Mar 2015
DOI:10.1039/C5AN00283D
In this work, a facile and highly efficient on-line concentration strategy based on a coupling of field enhanced sample injection (FESI) and sweeping was developed for the determination of trace enantiomers (propranolol, PL) by nonaqueous capillary electrophoresis (NACE). In this FESI-sweeping method, the use of a sample of high acidity and low conductivity (pH* = 2.5, 4.0 μS cm−1) allowed for a large amount of analyte injection. Then, the concentration of the analytes was carried out by sweeping based on the interaction of an acid-labile anionic selector, di-n-butyl L-tartrate-boric acid complex acid, and cationic analytes. Simultaneously, the concentrated analytes were released and focused at the boundary of the acid sample solution and separation buffer due to the decomposition of the selector in the acid sample solution. Under the optimum conditions, a 21000-fold sensitivity enhancement upon normal capillary zone electrophoresis (CZE) was achieved for PL enantiomers. The detection limits of R-propranolol and S-propranolol were 0.26 ng mL−1 and 0.31 ng mL−1, respectively. Eventually, the FESI-sweeping method was applied to detect PL enantiomers in plasma, saliva, and urine.
Co-reporter:Meijuan Liang, Yonglei Chen, Haijuan Zhang, Xiaoying Niu, Laifang Xu, Cuiling Ren and Xingguo Chen
Analyst 2015 vol. 140(Issue 19) pp:6711-6719
Publication Date(Web):19 Aug 2015
DOI:10.1039/C5AN01378J
A novel and effective ratiometric fluorescence strategy was developed for rapidly, sensitively and selectively probing sulfide anions (S2−). A dual-emission nanosensor was prepared by covalently attaching fluorescent carbon nanoparticles (CNPs) to gold nanoclusters (Au NCs), triggering the sensing mechanism of fluorescence resonance energy transfer (FRET) from CNPs (donor) to Au NCs (acceptor). Once S2− was added, considerable fluorescence recovery of CNPs and quenching of Au NCs were observed due to the inhibition of FRET progress via the formation of Au2S. The ratiometric probe showed good, specific S2− sensing behavior and high sensitivity with a detection limit of 18 nM. Significantly, the assay was successfully employed to determine the S2− content in biological and water samples, presenting immense promise in the biological and environmental fields.
Co-reporter:Su-dai Ma, Jie Feng, Wen-jie Qin, Yu-yun Ju and Xing-guo Chen
RSC Advances 2015 vol. 5(Issue 66) pp:53514-53523
Publication Date(Web):10 Jun 2015
DOI:10.1039/C5RA09114D
In this paper, core–shell polydopamine (PDA)-encapsulated CuFe2O4 (CuFe2O4@PDA) magnetic nanoparticles (MNPs) were synthesized through in situ self-polymerization for the first time. The size of the core–shell product can be controlled by tuning the dopamine monomer concentration. The formation of a PDA layer effectively enhanced the catalytic performance and provided a large specific surface area which offered more active sites for the effective interaction. The as-synthesized CuFe2O4@PDA MNPs were characterized and their catalytic activity was evaluated using the degradation of methylene blue (MB) in the presence of H2O2 as a model reaction. The experimental results showed that MB could be degraded efficiently using CuFe2O4@PDA MNPs as a catalyst. Under the optimized conditions, the degradation efficiency of MB was above 97%. Furthermore, a possible reaction mechanism was discussed. Finally, the catalyst was used for effective degradation of MB in a Yellow River water sample, which indicates its potential for practical applications in water pollutant removal and environmental remediation.
Co-reporter:Li Su, Wenjie Qin, Huige Zhang, Zia Ur Rahman, Cuiling Ren, Sudai Ma, Xingguo Chen
Biosensors and Bioelectronics 2015 Volume 63() pp:384-391
Publication Date(Web):15 January 2015
DOI:10.1016/j.bios.2014.07.048
•MFe2O4 (M=Mg, Ni, Cu) MNPs were found to possess the peroxidase/catalase-like activities.•MFe2O4 (M=Mg, Ni, Cu) MNPs could catalyzed H2O2 to produce OH and oxygen in the acidic condition.•As mimic peroxidase, MFe2O4 MNPs shows some advantages, such as stability and rapid separation.•A simple and selective colorimetric method for glucose determination in urine sample was developed.MFe2O4 (M=Mg, Ni, Cu) magnetic nanoparticles (MNPs) were found to have catalytic activities similar to those of biological enzymes such as catalase and peroxidase. These nanomaterials, as bifunctional catalase/peroxidases (KatGs), not only could catalyze H2O2 to produce hydroxyl radicals, which oxidized peroxidase substrate to produce color, but also could catalyze the decomposition reaction of H2O2 into water and oxygen directly in the same condition through the catalase-like activity. And it was also found that the amount of generated hydroxyl radicals and oxygen was related to the concentration of MFe2O4 (M=Mg, Ni, Cu) MNPs. The peroxidase-like catalytic behavior of MFe2O4 MNPs was analyzed in detail. Under the optimized conditions, NiFe2O4 MNPs were used as a colorimetric biosensor for the detection of 9.4×10−7–2.5×10−5 mol L−1 glucose with a limit of detection (LOD) of 4.5×10−7 mol L−1. The sensor was successfully applied to glucose detection in urine sample.
Co-reporter:Haijuan Zhang, Yonglei Chen, Meijuan Liang, Laifang Xu, Shengda Qi, Hongli Chen, and Xingguo Chen
Analytical Chemistry 2014 Volume 86(Issue 19) pp:9846
Publication Date(Web):September 11, 2014
DOI:10.1021/ac502446m
Carbon quantum dots (C-Dots) have drawn extensive attention in recent years due to their stable physicochemical and photochemical properties. However, the development of nitrogen-doped carbon quantum dots (N-doped C-Dots) is still on its early stage. In this paper, a facile and high-output solid-phase synthesis approach was proposed for the fabrication of N-doped, highly fluorescent carbon quantum dots. The obtained N-doped C-Dots exhibited a strong blue emission with an absolute quantum yield (QY) of up to 31%, owing to fluorescence enhancement effect of introduced N atoms into carbon dots. The strong coordination of oxygen-rich groups on N-doped C-Dots to Fe3+ caused fluorescence quenching via nonradiative electron-transfer, leading to the quantitative detection of Fe3+. The probe exhibited a wide linear response concentration range (0.01–500 μM) to Fe3+ with a detection limit of 2.5 nM. Significantly, the N-doped C-Dots possess negligible cytotoxicity, excellent biocompatibility, and high photostability. All these features are favorable for label-free monitoring of Fe3+ in complex biological samples. It was then successfully applied for the fluorescence imaging of intracellular Fe3+. As an efficient chemosensor, the N-doped C-Dots hold great promise to broaden applications in biological systems.
Co-reporter:Hai-juan Zhang, Sheng-da Qi, Xiao-ying Niu, Jing Hu, Cui-ling Ren, Hong-li Chen and Xing-guo Chen
Catalysis Science & Technology 2014 vol. 4(Issue 9) pp:3013-3024
Publication Date(Web):16 Apr 2014
DOI:10.1039/C4CY00072B
Separation and recycling of catalysts after catalytic reactions are critically required to reduce the cost of catalysts as well as to avoid the generation of waste in industrial applications. In this paper, ultrafine noble metallic nanoparticles are incorporated into cauliflower-like porous magnetic metal–organic frameworks (MOFs). With the restriction effects of the pore/surface structure in the MOFs, “surfactant-free” metallic nanoparticles are successfully obtained on a 2–3 nm scale. In addition, both the thickness of MOFs shell and the content of noble metallic NPs are tunable on the MOFs coating. Moreover, the microspheres exhibit excellent performance for the catalytic reduction of p-nitrophenol with a turnover frequency of 3094 h−1. The uniform cavities in the MOFs shell provide docking sites for p-nitrophenol and act as confinement nanoreactors, which greatly improves the catalytic performance. Most importantly, the magnetically responsive microspheres can be easily recovered by a magnetic field and show excellent reusability. The as-prepared catalyst also shows good activity for the reduction of other nitrobenzenes. Consequently, this work provides a highly active, magnetically isolable, and recyclable catalyst, which can be used for various catalytic industrial processes. The fundamental model can be further employed in a variety of biomedical fields including drug delivery and biological molecules separation.
Co-reporter:Haijuan Zhang, Shengda Qi, Yalei Dong, Xiaojiao Chen, Yinyin Xu, Yanhua Ma, Xingguo Chen
Food Chemistry 2014 Volume 151() pp:429-434
Publication Date(Web):15 May 2014
DOI:10.1016/j.foodchem.2013.11.016
•We used a novel ionic liquid [BMIM]MR for nitrite sensing for the first time.•60-fold improvement of sensitivity was obtained of nitrite detection.•Activation energy and the apparent rate constant were also investigated.•Trace amounts of nitrite in some significant real samples were determined.•The method could be deployed in environmental and food monitoring.This paper describes a colorimetric approach to determine trace amounts of nitrite in water supplies, meat and dairy products using 1-butyl-3-methylimidazolium-modified methyl red ([BMIM]MR) as a colour reagent. The technique capitalises on the catalytic effect of nitrite on the oxidative degradation of [BMIM]MR by potassium bromate in acidic media. The absorbances were proportional to nitrite concentrations in the range of 8.70 × 10−2 to 4.17 μM with a detection limit of 1.64 × 10−2 μM. Compared with the method using methyl red as a colour reagent, 60 times improvement of sensitivity was obtained. Activation energy and the apparent rate constant for the catalytic reaction are 61.11 kJ mol−1 and 1.18 × 104 s−1, respectively. The proposed method was successfully applied for the analysis of nitrite in Yellow River water, chicken, and milk with recoveries ranging from 96% to 105%.
Co-reporter:Yuyun Ju, Xi Li, Jie Feng, Yanhua Ma, Jing Hu, Xingguo Chen
Applied Surface Science 2014 Volume 316() pp:132-140
Publication Date(Web):15 October 2014
DOI:10.1016/j.apsusc.2014.07.152
Highlights
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In situ growth of Au NPs on GO via one pot reduction of Au3+ by Cu+ was first achieved.
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GO@NH2-Au NCs exhibit high catalytic activity for reduction of 4-NP.
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GO@NH2-Au NCs show high cycle stabilization during the catalytic reduction.
Co-reporter:Zia ur Rahman, Yanhua Ma, Jing Hu, Yinyin Xu, Weifeng Wang and Xingguo Chen
RSC Advances 2014 vol. 4(Issue 10) pp:5012-5020
Publication Date(Web):10 Dec 2013
DOI:10.1039/C3RA44434A
The effect of gold nanoseeds with different sizes on the gold shell was investigated. Gold nanoparticles of two different sizes (∼3 nm and ∼15 nm) were prepared and attached to the surface of amine functionalized silica coated iron oxide nanoparticles. The gold nanoparticles assembled on the surface were used as seeds for further gold shell formation. It was observed that the amount of Au attached to iron oxide nanoparticles is higher for bigger gold nanoseeds as compared to smaller gold nanoseeds. Similarly, after the formation of gold shell, a higher amount of Au was found for larger gold nanoparticles. However, both transmission electron microscopy (TEM) and scanning electron microscopy (SEM) results show that a complete, uniform, and compact gold shell was formed in the case of using small gold nanoseeds, but for larger gold nanoseeds the shell formed was discontinuous and was not uniform, while most of the gold nanoparticles were found to be aggregated on the surface. The nanocomposites showed high efficiency in catalysis for the reduction of 4-nirophenol, among which Nanocomp-2, with a thin stable gold shell showed excellent catalytic activity and reusability. All of the nanocomposites have high magnetization values and can be easily separated from the reaction mixture using a magnet and can be reused.
Co-reporter:Wenjie Qin, Li Su, Chen Yang, Yanhua Ma, Haijuan Zhang, and Xingguo Chen
Journal of Agricultural and Food Chemistry 2014 Volume 62(Issue 25) pp:5827-5834
Publication Date(Web):June 2, 2014
DOI:10.1021/jf500950p
In this paper, we first discovered that Co3O4 nanoparticles (NPs) possess intrinsic oxidase-like activity and can catalytically oxidize peroxidase substrates, such as 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and 3,3′,5,5′-tetramethylbenzidine (TMB), to form colored products, in the absence of exogenously added H2O2. The presence of sulfite inhibited the TMB–O2–Co3O4 NPs reaction system and caused a change in color of the reaction system. On the basis of this phenomenon, a colormetric approach to detect sulfite was established with a good linear relationship ranging from 0.2 × 10–6 to 1.6 × 10–5 M and a detection limit of 5.3 × 10–8 M. The method was used to detect sulfite in foods. Good recoveries ranging from 93.8% to 100.5% were obtained. Furthermore, the mechanism was studied and results showed that the oxidase-like activity of the Co3O4 NPs was not from •OH or O2•– radical generated. It may probably originate from their ability to transfer an electron between the peroxidase substrate and oxygen absorbed on the surface of the Co3O4 NPs.
Co-reporter:Jinmin Zheng, Yalei Dong, Weifeng Wang, Yanhua Ma, Jing Hu, Xiaojiao Chen and Xingguo Chen
Nanoscale 2013 vol. 5(Issue 11) pp:4894-4901
Publication Date(Web):22 Mar 2013
DOI:10.1039/C3NR01075A
In this work, a facile approach was successfully developed for in situ catalyzing Au nanoparticles loaded on Fe3O4@SiO2 magnetic nanospheres via Sn2+ linkage and reduction. After the Fe3O4@SiO2 MNPs were first prepared via a sol–gel process, only one step was needed to synthesize the Fe3O4@SiO2–Au magnetic nanocomposites (Fe3O4@SiO2–Au MNCs), so that both the synthesis step and the reaction cost were remarkably decreased. Significantly, the as-synthesized Fe3O4@SiO2–Au MNCs showed high performance in the catalytic reduction of 4-nitrophenol to 4-aminophenol and could be reused for several cycles with convenient magnetic separability. This approach provided a useful platform based on Fe3O4@SiO2 MNPs for the fabrication of Au or other noble metal magnetic nanocatalysts, which would be very useful in various catalytic reductions.
Co-reporter:Yinyin Xu, Laifang Xu, Shengda Qi, Yalei Dong, Zia ur Rahman, Hongli Chen, and Xingguo Chen
Analytical Chemistry 2013 Volume 85(Issue 23) pp:11369
Publication Date(Web):November 4, 2013
DOI:10.1021/ac402254u
Because of the unusual properties of the structure, the metal organic frameworks (MOFs) have received great interest in separation science. However, the most existing methods for the applications of MOFs in separation science require an off-line procedure to prepare the materials. Here, we report an in situ, layer-by-layer self-assembly approach to fabricate MIL-100(Fe) coated open tubular (OT) capillary columns for capillary electrochromatography. By a controllable manner, the OT capillary columns with a tailored MIL-100(Fe) coating have been successfully synthesized. The results of SEM, XRD, FT-IR, and ICP-AES indicated that MIL-100(Fe) was successfully grafted on the inner wall of the capillary. Some neutral, acidic and basic analytes were used to evaluate the performance of the MIL-100(Fe) coating OT capillary column. Because of the size selectivity of lattice aperture and hydrophobicity of the organic ligands, three types of analytes were well separated with this novel MIL-100(Fe) coating OT capillary column. For three consecutive runs, the intraday relative standard deviations (RSDs) of migration time and peak areas were 0.4–4.6% and 1.2–6.6%, respectively. The interday RSDs of migration time and peak areas were 0.6–8.0% and 2.2–9.5%, respectively. The column-to-column reproducibility of retention time was in range of 0.6–9.2%. Additionally, the 10 cycles OT capillary column (10-LC) could be used for more than 150 runs with no observable changes on the separation efficiency.
Co-reporter:Xi Li, Yuyun Ju, Yinyin Xu, Weifeng Wang, Yalei Dong, Yanhua Ma, Xingguo Chen
Analytica Chimica Acta 2013 Volume 789() pp:100-106
Publication Date(Web):30 July 2013
DOI:10.1016/j.aca.2013.06.031
•A novel CE strategy combined chitosan trapping and CTAB assisted sample stacking.•Validation parameters of this method were investigated and satisfactory.•The method was used to detect organic acids in real Plateau alfalfa roots samples.In this paper, four organic acids constituents of Plateau alfalfa roots have been identified and detected by a novel capillary electrophoresis (CE) strategy which combined chitosan (CS) trapping and cetyltrimethyl ammonium bromide (CTAB) assisted sample stacking. Under the optimized condition, organic acids, i.e., aconitic acid, gallic acid, citric acid and l-malic acid were concentrated and separated within 3 min. Validation parameters of this method (such as detection limits, linearity and precision) were also investigated and the limit of detection (LOD) was 2.41–53.9 ng mL−1. Linearity was obtained over the magnitude range of 5–4000 ng mL−1 approximately for different organic acids and 3 × 102–1.5 × 104 folds enrichment was achieved. The method has been applied to the determination of organic acids in roots of normal grown Plateau alfalfa and stressing affected Plateau alfalfa. Satisfactory results and recoveries were obtained in the analysis without costly and complicated sample pretreatment.
Co-reporter:Yin-yin Xu, Xiao-ying Niu, Ya-lei Dong, Hui-ge Zhang, Xi Li, Hong-li Chen, Xing-guo Chen
Journal of Chromatography A 2013 Volume 1284() pp:180-187
Publication Date(Web):5 April 2013
DOI:10.1016/j.chroma.2013.01.105
A novel coated capillary was prepared by immobilizing graphene oxide (GO) on the fused-silica capillary (75 μm i.d.) which was derivatized by 3-aminopropyl-trimethoxysilane (APTMS). The bare capillary, APTMS modified capillary (NH2-capillary) and GO coated capillary (GO-capillary) were characterized by streaming potentials (SPs), fluorescence microscope and scanning electron microscope (SEM). The results indicated that the capillary was successfully modified with GO sheets via covalent bonding and electrostatic effect. Compared with bare capillary, greater separation efficiency was achieved by GO-capillary column as a result of the increasing interactions between the small organic molecules and the inner wall of the GO-capillary column originated from the π–π electrostatic stacking. For three consecutive runs, the intra-day relative standard deviations (RSDs) of migration time and peak areas were 0.6–4.3% and 2.8–9.3%, respectively. The inter-day relative standard deviations of migration time and peak areas were 0.2–8.3% and 4.5–9.6%. Additionally, one GO-capillary column could be used for more than 100 runs with no observable changes on the separation efficiency.Highlights► The GO-capillary column was prepared and characterized by various methods. ► Baseline separation of small organic molecules was obtained by GO-capillary column. ► The GO-capillary column was used more than 100 runs with good separation efficiency.
Co-reporter:Li-Juan Wang, Xiu-Feng Liu, Qie-Nan Lu, Geng-Liang Yang, Xing-Guo Chen
Journal of Chromatography A 2013 Volume 1284() pp:188-193
Publication Date(Web):5 April 2013
DOI:10.1016/j.chroma.2013.02.006
A chiral recognition mechanism of ion-pair principle has been proposed in this study. It rationalized the enantioseparations of some basic analytes using the complex of di-n-butyl l-tartrate and boric acid as the chiral selector in methanolic background electrolytes (BGEs) by nonaqueous capillary electrophoresis (NACE). An approach of mass spectrometer (MS) directly confirmed that triethylamine promoted the formation of negatively charged di-n-butyl l-tartrate–boric acid complex chiral counter ion with a complex ratio of 2:1. And the negatively charged counter ion was the real chiral selector in the ion-pair principle enantioseparations. It was assumed that triethylamine should play its role by adjusting the apparent acidity (pH*) of the running buffer to a higher value. Consequently, the effects of various basic electrolytes including inorganic and organic ones on the enantioseparations in NACE were investigated. The results showed that most of the basic electrolytes tested were favorable for the enantioseparations of basic analytes using di-n-butyl l-tartrate–boric acid complex as the chiral ion-pair selector.Highlights► A chiral recognition mechanism of ion-pair principle was proposed. ► A MS approach verified the formation of negatively charged complex chiral selector. ► The MS approach determined the complex ratio of the chiral selector. ► Various basic electrolytes were useful for the enantioseparations.
Co-reporter:Ximin Zhou, Xi Li, Xingguo Chen
Dyes and Pigments 2013 Volume 98(Issue 2) pp:212-220
Publication Date(Web):August 2013
DOI:10.1016/j.dyepig.2013.01.023
Orange G (OG) was used as a model compound to investigate the binding mechanism between azo dye and human serum albumin (HSA) using a variety of methods. These included nuclear magnetic resonance (NMR), saturation transfer difference (STD)-NMR, steady-state fluorescence, UV–vis absorption, circular dichroism (CD), Fourier transform infrared (FT-IR), three-dimensional fluorescence, time-resolved fluorescence spectroscopy, and molecular modeling method under simulated physiological conditions. The data of NMR and STD-NMR indicated that OG was indeed bound to HSA and located in the hydrophobic pocket of HSA. The fluorescence quenching data showed that the binding of OG and HSA quenched the intrinsic fluorescence of HSA, and the dynamic quenching constants were acquired. Thermodynamics analysis and molecular modeling studies suggested that GO bound to the site I on HSA molecule, and indicated the presence of hydrophobic forces. The alterations of protein conformational structures were further examined by synchronous fluorescence, UV–vis absorption, CD, FT-IR, three-dimensional fluorescence, and time-resolved fluorescence spectroscopy.Graphical abstractHighlights► STD-NMR, 1H NMR, optical spectroscopy and molecular modeling method were utilized. ► The bonding between OG and HSA was investigated qualitatively and quantitatively. ► The quenching mechanism for OG–HSA system was dynamic quenching mechanism. ► The molecular modeling and thermodynamic analysis determined the binding site.
Co-reporter:Qing Yang, Xi-min Zhou, Yi-shuo Zhu, Xing-guo Chen
Journal of Luminescence 2013 Volume 135() pp:335-338
Publication Date(Web):March 2013
DOI:10.1016/j.jlumin.2012.09.015
In this paper, glutathione (GSH) modified CdTe quantum dots (CdTe@GSH QDs) were synthesized in an aqueous solution. Then, the binding of the CdTe@GSH QDs to human serum albumin (HSA) was studied using the fluorescence spectroscopy. The quenching mechanism was investigated in terms of the association constants and basic thermodynamic parameters. The fluorescence data revealed that CdTe@GSH QDs could quench the intrinsic fluorescence of human serum albumin by a static quenching mechanism. Furthermore, alteration of the secondary protein structure in the presence of the QDs was confirmed by synchronous fluorescence spectra.Highlights► In this paper, the binding of the CdTe@GSH QDs to human serum albumin (HSA) was studied using a fluorescence spectroscopy. ► The quenching mechanism was investigated in terms of the association constants and basic thermodynamic parameters. ► Furthermore, alteration of the secondary protein structure in the presence of the QDs was confirmed by synchronous fluorescence spectra. ► The research can help us assess biological toxicity of QDs and further expand the application scope of QDs.
Co-reporter:Jinmin Zheng, Haijuan Zhang, Jichun Qu, Qian Zhu and Xingguo Chen
Analytical Methods 2013 vol. 5(Issue 4) pp:917-924
Publication Date(Web):03 Dec 2012
DOI:10.1039/C2AY26391B
In this study, a novel colorimetric method for rapid, sensitive and low-cost detection of glyphosate was developed using cysteamine-stabilized gold nanoparticles (CS-AuNPs). The CS-AuNPs could be aggregated easily in the presence of glyphosate through electrostatic interaction in acidic medium, resulting in a shift in the surface plasmon band and a consequent color change from red to blue (or purple). Therefore, the content of glyphosate could be determined by monitoring with the naked eyes or a UV-Vis spectrophotometer. The detection limit of the present method for glyphosate was 5.88 × 10−8 M, with the linear range of 0.500–7.00 μM. The proposed method is a promising approach for on-site screening of glyphosate content in environmental water samples without using any costly instruments.
Co-reporter:Li Su, Jie Feng, Ximin Zhou, Cuiling Ren, Honghong Li, and Xingguo Chen
Analytical Chemistry 2012 Volume 84(Issue 13) pp:5753
Publication Date(Web):June 13, 2012
DOI:10.1021/ac300939z
In this paper, we discovered that ZnFe2O4 magnetic nanoparticles (MNPs) possess intrinsic peroxidase-like activity. ZnFe2O4 MNPs exhibit several advantages such as high catalytic efficiency, good stability, monodispersion, and rapid separation over other peroxidase nanomimetics and horseradish peroxidase (HRP). ZnFe2O4 MNPs were used as a colorimetric biosensor for the detection of urine glucose. This method is simple, inexpensive, highly sensitive, and selective for glucose detection using glucose oxidase (GOx) and ZnFe2O4 MNPs with a linear range from 1.25 × 10–6 to 1.875 × 10–5 mol L–1 with a detection limit of 3.0 × 10–7 mol L–1. The color change observable by the naked eyes based on the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) is the principle for the sensing of urine glucose level.
Co-reporter:Yanhua Ma, Zhenyang Zhang, Cuiling Ren, Guoyun Liu and Xingguo Chen
Analyst 2012 vol. 137(Issue 2) pp:485-489
Publication Date(Web):23 Nov 2011
DOI:10.1039/C1AN15718C
In this paper, a novel and simple colorimetric method for the determination of reduced glutathione (GSH) based on Fe3O4 magnetic nanoparticles (MNPs) as peroxidase mimetics was developed. The Fe3O4 MNPs prepared via a coprecipitation method, which possess intrinsic peroxidase-like activity, were used as a catalyst in the color development reaction of a peroxidase substrate 2,2′-azino-bis(3-thylbenzo-thiazoline-6-sulfonic acid) diammonium salt (ABTS) and H2O2. The existence of GSH can consume H2O2 and cause a color change of the reaction system which can be detected by the naked eye. Accordingly, the GSH can be detected by measuring the wastage of H2O2. A good linear relationship was obtained from 3.0 to 30.0 μM for GSH. Good recoveries ranging from 96.7 to 107% were obtained. Furthermore, it was used to detect GSH in A549 cells.
Co-reporter:Ximin Zhou, Wenjuan Lü, Li Su, Yalei Dong, Qianfeng Li and Xingguo Chen
Organic & Biomolecular Chemistry 2012 vol. 10(Issue 41) pp:8314-8321
Publication Date(Web):28 Aug 2012
DOI:10.1039/C2OB25967B
The binding affinity between hydroxyproline (Hyp) and human serum albumin (HSA) was investigated under simulated physiological conditions, using molecular modeling in combination with steady-state fluorescence, synchronous fluorescence, time-resolved fluorescence, UV-vis absorption, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopy. Molecular modeling studies suggested that the Hyp molecule was situated within subdomain IIA of HSA. The fluorescence quenching analysis indicated that the fluorescence of HSA was quenched by Hyp with a dynamic quenching mechanism. The binding constants were calculated according to Scatchard's equation and implied that Hyp can bind to different binding sites on HSA. The thermodynamic analysis implied that hydrophobic forces were the main interaction in the Hyp–HSA system, which was found to be in line with the results of molecular modeling. Furthermore, the conformational structure of HSA was changed with various amounts of Hyp, which was confirmed by synchronous fluorescence, UV-vis absorption, CD, and FT-IR spectra.
Co-reporter:Ximin Zhou, Qing Yang, Xiaoyun Xie, Qin Hu, Fengming Qi, Zia Ur Rahman, Xingguo Chen
Dyes and Pigments 2012 Volume 92(Issue 3) pp:1100-1107
Publication Date(Web):March 2012
DOI:10.1016/j.dyepig.2011.08.012
In this study, the interaction between C.I. Acid Orange 7 (AO7) and human serum albumin (HSA) was firstly investigated using nuclear magnetic resonance (NMR) spectroscopy in combination with fluorescence quenching spectroscopy, three-dimensional fluorescence spectroscopy, UV–vis absorption spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD) spectroscopy and molecular modeling method in vitro. The results of NMR data confirmed that AO7 indeed interacted with HSA, and the hydrophobic portion of AO7 should be embedded to the hydrophobic pocket of HSA. The fluorescence quenching analysis revealed that AO7 can bind to HSA. The conformational change of HSA in the presence of AO7 was confirmed by synchronous fluorescence, three-dimensional fluorescence, UV–vis absorption, FT-IR and CD spectra. The binding distance between AO7 and tryptophan residue of HSA was calculated by the efficiency of fluorescence resonance energy transfer. Molecular modeling showed that hydrophobic force and hydrogen bonds were the major interaction between AO7 and HSA.The interaction mechanism of C.I. Acid Orange 7 (AO7) with human serum albumin (HSA) was firstly investigated by NMR spectroscopy, multi-spectroscopic and molecular modeling method under simulative physiological conditions. Molecular modeling study suggested that the binding site was located in the hydrophobic pocket of HSA, and AO7 can bind HSA through the hydrophobic force and hydrogen bonds.Highlights► The binding of AO7 to HSA was studied by NMR, fluorescence, FT-IR, UV–vis and CD. ► The fluorescence data and molecular modeling revealed that AO7 can bind to HSA. ► The addition of AO7 can induce the conformational changes of HSA. ► Both hydrophobic force and hydrogen bonds play a major role in the interaction.
Co-reporter:Ya-lei Dong, Na Yan, Xi Li, Xi-min Zhou, Lei Zhou, Hai-juan Zhang, Xing-guo Chen
Journal of Chromatography A 2012 Volume 1233() pp:156-160
Publication Date(Web):13 April 2012
DOI:10.1016/j.chroma.2012.02.030
Many reports have focused on the determination of hydroxyproline (Hyp) in blood plasma, urine sample, meat and meat products, however, there are few concerned with the Hyp assay in dairy products for food quality assurance up to now. In this paper, we described a sensitive and automated approach for the determination of Hyp in milk powder, liquid milk, milk drink and soymilk powder samples by micellar electrokinetic chromatography (MEKC) based on in-capillary derivatization for the first time. Under the optimal conditions, derivatization and separation procedure could be completed within 7 min and the detection limit for Hyp was 1.6 ± 0.5 ng mL−1. Comparing with the existing alternatives, the present method exhibited some relevant advantages, including full automation, satisfactory sensitivity, and short analysis time for Hyp assay in dairy products.
Co-reporter:Ya-lei Dong, Hui-ge Zhang, Zia Ur Rahman, Hai-juan Zhang, Xiao-jiao Chen, Jing Hu, Xing-guo Chen
Journal of Chromatography A 2012 Volume 1265() pp:176-180
Publication Date(Web):23 November 2012
DOI:10.1016/j.chroma.2012.09.082
In this paper, we established a new on-line method using micelle to solvent stacking (MSS) technique combining with large amount sample electrokinetic stacking injection (LASEKSI) for the analysis of cationic molecules. In this MSS–LASEKSI, by modulating the integral EOF across the capillary, a equilibrium state was formed and can be maintained for a long time, leading to the continuous stacking of the analytes on the basis of MSS. Thereby, an extremely large amount sample was permitted to be injected into the capillary and then an improved enrichment fold can be achieved comparing with the each case. The variables affecting the performance of MSS–LASEKSI were investigated and discussed. Under the optimized conditions, 6.3 × 103- and 6.4 × 102-fold enrichment in peak heights upon normal CZE method (injected at 0.5 psi for 3 s) and number of plates of 2.9 × 106 and 6.5 × 105 were attained for berberine and theophylline, respectively. The developed method described here may provide prospects for exploiting a new concentration technique to achieve higher enrichment factor.Highlights► This paper builds a hyphenated MSS enrichment technique coupling with LSAEKSI for CE. ► 6.3 × 103-fold enrichment in peak height was obtained under the optimum conditions. ► This method provides prospects to achieve higher enrichment fold.
Co-reporter:Li-Juan Wang, Juan Yang, Geng-Liang Yang, Xing-Guo Chen
Journal of Chromatography A 2012 Volume 1248() pp:182-187
Publication Date(Web):27 July 2012
DOI:10.1016/j.chroma.2012.05.061
In this paper, twelve dialkyltartrate–boric acid complexes and two polyols–boric acid complexes were in situ synthesized by the reaction of different dialkyltartrates or polyols with boric acid in methanol containing triethylamine. All of the twelve dialkyltartrate–boric acid complexes were found to have relatively good chiral separation performance in nonaqueous capillary electrophoresis (NACE). Their chiral recognition effects in terms of both enantioselectivity (α) and resolution (Rs) were similar when the number of carbon atoms was below six in the alkyl group of alcohol moiety. The dialkyltartrates containing alkyl groups of different structures but the same number of carbon atoms, i.e. one of straight chain and one of branched chain, also provided similar chiral recognition effects. Furthermore, it was demonstrated for the first time that two methanol insoluble polyols, d-mannitol and d-sorbitol, could react with boric acid to prepare chiral ion-pair selectors using methanol as the solvent medium.Highlights► Twelve dialkyltartrate–boric acid complexes were evaluated as chiral selectors. ► All of the dialkyltartrate–boric acid complexes showed similar chiral recognition. ► Six β-blockers and five β-agonists obtained relatively good enantioseparation. ► Polyols–boric acid complexes were used as chiral selectors firstly in NACE.
Co-reporter:Xi-Min Zhou, Wen-Juan Lü, Li Su, Zhi-Jie Shan, and Xing-Guo Chen
Journal of Agricultural and Food Chemistry 2012 Volume 60(Issue 4) pp:1135-1145
Publication Date(Web):December 29, 2011
DOI:10.1021/jf204380r
As endocrine-disrupting chemicals, a few frequently used phthalate plasticizers were banned or restricted for use as additives in food in some countries. The interaction mechanisms between three phthalate plasticizers with human serum albumin (HSA) were studied by fluorescence (quenching, synchronous, and three-dimensional), UV–vis absorption, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopy, in combination with molecular modeling under simulative physiological conditions, respectively. The results obtained from fluorescence quenching data revealed that the plasticizers–HSA interaction altered the conformational strcture of HSA. Meanwhile, the alterations of HSA secondary structure in the presence of phthalate plasticizers were investigated. The binding distances for the plasticizers–HSA system were provided by the efficiency of fluorescence resonance energy transfer. Furthermore, the thermodynamic analysis implied that hydrophobic forces were the main interaction for the plasticizers–HSA system, which agreed well with the results from the molecular modeling study.
Co-reporter:Yan-Ping Chang, Cui-Ling Ren, Ji-Chun Qu, Xing-Guo Chen
Applied Surface Science 2012 Volume 261() pp:504-509
Publication Date(Web):15 November 2012
DOI:10.1016/j.apsusc.2012.08.045
Abstract
In the present study, Fe3O4/graphene nanocomposite was prepared by solvothermal method and characterized by transmission electron microscope, Fourier transform infrared spectrometer and vibration sample magnetometer. Effects of different factors, including initial solution pH, agitation time and adsorbate concentration, on adsorption capacity of Fe3O4/graphene nanocomposite for aniline and p-chloroaniline were investigated. Experimental results demonstrated aniline and p-chloroaniline could be effectively removed from aqueous solution by Fe3O4/graphene nanocomposite within 60 min without adjusting solution pH. The adsorption of aniline and p-chloroaniline onto Fe3O4/graphene nanocomposite obeyed pseudo-second-order kinetic model and Freundlich isotherm model. The saturation magnetization of the Fe3O4/graphene nanocomposite was about 120 emu g−1, which ensured the convenient magnetic separation after adsorption.
Co-reporter:Yonglei Chen;Wenjuan Lü;Xingguo Chen;Min Teng
Central European Journal of Chemistry 2012 Volume 10( Issue 3) pp:611-638
Publication Date(Web):2012 June
DOI:10.2478/s11532-012-0007-4
Co-reporter:Ji-chun Qu, Yan-ping Chang, Yan-hua Ma, Jin-min Zheng, Hong-hong Li, Qian-qian Ou, Cuiling Ren, Xing-guo Chen
Sensors and Actuators B: Chemical 2012 174() pp: 133-139
Publication Date(Web):
DOI:10.1016/j.snb.2012.08.045
Co-reporter:Hua-dong Zhu, Wenjuan Lü, Hong-hong Li, Yan-hua Ma, Shao-qiang Hu, Hong-li Chen and Xing-guo Chen
Analyst 2011 vol. 136(Issue 7) pp:1322-1328
Publication Date(Web):08 Feb 2011
DOI:10.1039/C0AN00592D
In this study, a cross-H-channel interface was constructed for coupling flow injection with capillary electrophoresis (FI–CE) to reduce sample requirement and sensitivity loss in the typical FI–CE. Based on this cross-H-channel interface, a new FI–CE system was established, in which sample introduction was performed by directly injecting sample solution along a thin capillary (50 μm, i.d.) to the interface from an injection syringe. The sample requirement was reduced distinctly and usual sample dilution in the sample transport process was obviously decreased, thereby spontaneously enhancing the sensitivity. Moreover, because of the unique construction of the cross-H-channel interface, field amplified sample stacking (FASS) and high-speed CE were skillfully combined to further improve the sensitivity and to shorten separation time. The versatility of this new FI–CE was demonstrated by determination of ephedrine (E) and pseudoephedrine (PE) in human urine. Up to 45 repeated injections per hour and clearly baseline separation of E and PE in less than 1 min were achieved, giving limits of detection (LODs) of 0.23 and 0.21 μg mL−1 for E and PE, respectively, and yielding relative standard deviation (RSD) values of the migration time and the peak height (n = 5) of 2.6% and 3.1% for E, 2.3% and 3.3% for PE, respectively. In contrast to typical FI–CE, approximately 8–250-fold decreases in sample volume requirement, 7-fold shortening in separation time and 50-fold improvements in sensitivity were obtained.
Co-reporter:Xiaoru Wang, Xiaoyun Xie, Cuiling Ren, Ying Yang, Xiangmei Xu, Xingguo Chen
Food Chemistry 2011 Volume 127(Issue 2) pp:705-710
Publication Date(Web):15 July 2011
DOI:10.1016/j.foodchem.2010.12.128
In the present study, the interaction of vanillin and human serum albumin (HSA) has been characterised by molecular modelling, fluorescence, Fourier transform infrared (FT-IR) and circular dichroism (CD) spectroscopic methods. The results of molecular modelling suggested that vanillin was located within the binding pocket of subdomain IIA of HSA mainly by hydrophobic forces. The quenching of HSA fluorescence takes place with a binding constant (K) of 8.8, 7.7, 5.7, 4.2 × 104 M−1 at four different temperatures (288, 298, 308, 318 K), respectively. Meanwhile, the number of binding site (n ≈ 1) was also obtained from fluorescence titration data. The enthalpy change ΔH0 and the entropy change ΔS0 were calculated to be −20 kJ mol−1 and 5.8 J mol−1 K−1 according to the Van’t Hoff equation. Furthermore, the alterations of protein secondary structure in the presence of vanillin were explored by FT-IR and CD spectra.Research highlights► Partial binding parameters of vanillin to HSA were revealed by molecular docking. ► Physicochemical properties of vanillin to HSA were detected by fluorescence. ► Secondary structure of HSA were measured by CD and FT-IR spectroscopic methods.
Co-reporter:Hua-dong Zhu, Wen-juan Lü, Hong-hong Li, Yan-hua Ma, Shao-qiang Hu, Hong-li Chen, Xing-guo Chen
Journal of Chromatography A 2011 Volume 1218(Issue 34) pp:5867-5871
Publication Date(Web):26 August 2011
DOI:10.1016/j.chroma.2011.06.106
This paper for the first time describes the development of micelle to solvent stacking (MSS) to nonaqueous capillary electrophoresis (NACE). In this proposed MSS-NACE, sodium dodecyl sulfate (SDS) micelles transport, release, and focus analytes from the sample solution to the running buffer using methanol as their solvent. After the focusing step, the focused analytes were separated via NACE. The focusing mechanism and influencing factors were discussed using berberine (BBR) and jatrorrhizine (JTZ) as model compounds. And the optimum condition was obtained as following: 50 mM ammonium acetate, 6% (v/v) acetic acid and 10 mM SDS in redistilled water as sample matrix, 50 mM ammonium acetate and 6% (v/v) acetic acid in pure methanol as the running buffer, −20 kV focusing voltage with 30 min focusing time. Under these conditions, this method afforded limits of detection (S/N = 3) of 0.002 μg/mL and 0.003 μg/mL for BBR and JTZ, respectively. In contrast to conventional NACE, the concentration sensitivity was improved 128–153-fold.
Co-reporter:Yang Hui, Xi Li, Xingguo Chen
Journal of Chromatography A 2011 Volume 1218(Issue 34) pp:5858-5866
Publication Date(Web):26 August 2011
DOI:10.1016/j.chroma.2011.06.100
The light-induced cis–trans isomerization of rhapontigenin (RHA) and its glucoside rhaponticin (RHA-Glc) were evaluated under ultraviolet (UV) light irradiation. A simple and rapid capillary electrophoresis method was developed for the kinetic study of four stilbenes (both cis and trans form of RHA and RHA-Glc). These analyses were achieved by using β-cyclodextrin (β-CD) modified capillary zone electrophoresis with diode array detector (CZE-DAD). The method provided reliable separations with a short analysis time of 3 min. The purity of individual compound was checked by UV spectral comparisons with known standards, and further confirmed by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. Furthermore, the UV absorbance and the molar absoptivity (ɛ) values were determined by UV–vis spectrophotometer to be 36824 L mol−1 cm−1 at λmax 324.5 nm for trans-RHA and 43894 L mol−1 cm−1 at λmax 325 nm for trans-RHA-Glc in methanol/water mixture solution (50%, v:v), respectively. CZE, UV–vis and NMR spectroscopy studies provided similar conclusions by considering the influence of irradiation time and the influence of irradiation wavelength.
Co-reporter:Hua-dong Zhu, Cui-ling Ren, Shao-qiang Hu, Xi-min Zhou, Hong-li Chen, Xing-guo Chen
Journal of Chromatography A 2011 Volume 1218(Issue 5) pp:733-738
Publication Date(Web):4 February 2011
DOI:10.1016/j.chroma.2010.11.060
In this paper, the co-solvent of methanol–water was used to facilitate the sodium dodecyl sulfate (SDS) micelles collapse, thereby inducing the on-line sample focusing technique of micelle to solvent stacking (MSS). To demonstrate this stacking method, the mechanism of micelles collapse in co-solvent was discussed. The details of the required conditions were investigated and the optimized conditions were: running buffer, 20 mM H3BO3 and 20 mM NaH2PO4 solution (pH 4.0); micellar sample matrix, 20 mM SDS, 20 mM H3BO3 and 20 mM NaH2PO4 solution (pH 4.0); co-solvent buffer, 20 mM H3BO3 and 20 mM NaH2PO4 in methanol/water (90:10, v/v). The validity of the developed method was tested using cationic alkaloid compounds (ephedrine and berberine) as model analytes. Under the optimized conditions, this proposed method afforded limits of detection (LODs) of 0.5 and 1.1 ng/mL with 300 and 1036-fold improvements in sensitivity for ephedrine and berberine, respectively, within 15 min.
Co-reporter:Ximin Zhou, Yuanyuan Yue, Qing Yang, Na Yan, Xingguo Chen
Journal of Luminescence 2011 Volume 131(Issue 6) pp:1222-1228
Publication Date(Web):June 2011
DOI:10.1016/j.jlumin.2011.02.009
The interaction mechanism of Acid Orange 6 (AO6) with human serum albumin (HSA) was investigated firstly by using fluorescence quenching technique, UV absorbance, circular dichroism (CD), Fourier transform infrared (FT-IR), three-dimensional fluorescence spectroscopy in combination with molecular modeling method under simulative physiological conditions. Fluorescence data indicated that there is a single class of binding sites between AO6 and HSA, and the alterations of HSA secondary structure in the presence of AO6 was confirmed by synchronous fluorescence, UV, CD, FT-IR and three-dimensional fluorescence spectra. The efficiency of fluorescence resonance energy transfer provided the binding distance (r) of 2.83 nm for AO6–HSA system. Furthermore, the thermodynamic parameters enthalpy change (ΔH0) and entropy change (ΔS0) for the reaction were calculated to be −5.77 kJ mol−1 and 109.42 J mol−1 K−1, respectively, according to Van't Hoff equation, these data suggested that both hydrophobic forces and hydrogen bonding play a major role in the binding of AO6 to HSA, which agrees well with the results of molecular modeling study. Experimental results showed that the interaction between AO6 and HSA induced a conformational change of HSA, which was proved by the qualitative and quantitative analysis data of different spectroscopic techniques under simulative physiological conditions.Research highlights► Utilized multi-spectroscopy technique and molecular modeling method. ► Investigated the interaction between AO6 and HSA qualitatively and quantitatively. ► The intrinsic fluorescence of HSA was quenched through dynamic quenching mechanism. ► The addition of AO6 can induce the conformational changes of HSA. ► Both hydrophobic forces and hydrogen bonding play a major role in the interaction.
Co-reporter:Qing Yang, Xi-min Zhou, Xing-guo Chen
Journal of Luminescence 2011 Volume 131(Issue 4) pp:581-586
Publication Date(Web):April 2011
DOI:10.1016/j.jlumin.2010.10.033
The binding of Eosin B to human serum albumin (HSA) was studied using molecular docking, fluorescence, UV–vis, circular dichroism (CD) and Fourier transform infrared (FT-IR) spectroscopy. The mechanism of interaction between Eosin B and HSA in terms of the binding parameters, the thermodynamic functions and the effect of Eosin B on the conformation of HSA were investigated. Protein-ligand docking study indicated that Eosin B bound to residues located in the subdomain IIA of HSA and Eosin B–HSA complex was stabilized by hydrophobic force and hydrogen bonding. In addition, fluorescence data revealed that Eosin B strongly quenched the intrinsic fluorescence of HSA through a static quenching procedure. Furthermore, alteration of the secondary structure of HSA in the presence of the dye was conformed by UV–vis, FT-IR and CD spectroscopy.
Co-reporter:Qin Wang, Yaheng Zhang, Huijun Sun, Hongli Chen, Xingguo Chen
Journal of Luminescence 2011 Volume 131(Issue 2) pp:206-211
Publication Date(Web):February 2011
DOI:10.1016/j.jlumin.2010.09.040
Study of the interaction between butyl p-hydroxybenzoate (butoben) and human serum albumin (HSA) has been performed by molecular modeling and multi-spectroscopic method. The interaction mechanism was predicted through molecular modeling first, then the binding parameters were confirmed using a series of spectroscopic methods, including fluorescence spectroscopy, UV–visible absorbance spectroscopy, circular dichroism (CD) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. The thermodynamic parameters of the reaction, standard enthalpy ΔH0 and entropy ΔS0, have been calculated to be −29.52 kJ mol−1 and −24.23 J mol−1 K−1, respectively, according to the Van’t Hoff equation, which suggests the van der Waals force and hydrogen bonds are the predominant intermolecular forces in stabilizing the butoben–HSA complex. Results obtained by spectroscopic methods are consistent with that of the molecular modeling study. In addition, alteration of secondary structure of HSA in the presence of butoben was evaluated using the data obtained from UV–visible absorbance, CD and FT-IR spectroscopies.Research highlights► The interaction between butyl p-hydroxybenzoate with HSA has been investigated for the first time. ► Molecular modeling study can provide theoretical direction for experimental design. ► Multi-spectroscopic method can provide the binding parameters and thermodynamic parameters. ► These results are important for food safety and human health when using parabens as a preservative.
Co-reporter:Yan-Ping Chang, Cui-Ling Ren, Qing Yang, Zhen-Yang Zhang, Li-Jun Dong, Xing-Guo Chen, De-Sheng Xue
Applied Surface Science 2011 Volume 257(Issue 20) pp:8610-8616
Publication Date(Web):1 August 2011
DOI:10.1016/j.apsusc.2011.05.031
Abstract
In this paper, a new adsorbent, hexadecyl functionalized magnetic silica nanoparticles (C16/SiO2–Fe3O4 NPs), was prepared by a facile method. The final product was characterized by X-ray diffractometer, transmission electron microscope, Fourier transform infrared spectrometer and vibration sample magnetometer. The preparation and adsorption conditions of the adsorbent were optimized. The adsorbent prepared maintaining volume ratio of tetraethylorthosilicate to hexadecyltrimethoxysilane at 1:0.5 and their total volume at 1100 μL exhibited high adsorption capacity. The optimum pH value for the adsorption experiments was 11.00. The adsorption behavior of Rhodamine 6G onto C16/SiO2–Fe3O4 NPs obeyed pseudo-second-order kinetic model and Langmuir isotherm. Thermodynamic data indicated that the adsorption process was spontaneous and exothermic. The adsorption capacity of the adsorbent could reach to 35.6 mg g−1, owing to the hydrophobic attraction and the enhanced electrostatic attraction. The saturation magnetization of the magnetic adsorbent was 35 emu g−1, which ensured the magnetic separation after adsorption.
Co-reporter:Jinhua Zhu;Huige Zhang;Shengda Qi;Xingguo Chen;Zhide Hu
Chromatographia 2011 Volume 73( Issue 5-6) pp:535-540
Publication Date(Web):2011 March
DOI:10.1007/s10337-011-1911-z
Liensinine (LIE), isoliensinine (ISO) and neferine (NEF) from embryo of the seed of Nelumbo nucifera Gaertn were first separated and quantitatively analyzed by micellar electrokinetic chromatography with internal standard (IS) using a cationic surfactant, tetradecyltrimethyl ammonium bromide (TTAB). Complete separation of the analytes was optimally achieved within 15 min using 40 mM sodium dihydrogenphosphate (pH 6.40) containing 10 mM TTAB and 15% (v/v) methanol as buffer. Tetrahydropalmatine was used as IS to improve the repeatability and linearity relativity. The IS method resulted in excellent linearity, with correlation coefficients of regression equations of 0.9997, 0.9997 and 0.9992 for LIE, ISO and NEF, respectively. Finally, two sample extraction methods were used to investigate the contents of different parts of the embryos.
Co-reporter:Li-Juan Wang, Shao-Qiang Hu, Qiao-Ling Guo, Geng-Liang Yang, Xing-Guo Chen
Journal of Chromatography A 2011 1218(9) pp: 1300-1309
Publication Date(Web):
DOI:10.1016/j.chroma.2011.01.003
Co-reporter:Ning Ding, Na Yan, Cuiling Ren and Xingguo Chen
Analytical Chemistry 2010 Volume 82(Issue 13) pp:5897
Publication Date(Web):June 7, 2010
DOI:10.1021/ac100597s
In this paper, a simple and rapid colorimetric method, which does not require any expensive and complex instruments, is established for the determination of melamine in dairy products. Lower than 2.5 ppm (the safety limit in the USA and EU) of melamine in real samples can be detected exactly with the recoveries in a range from 98−115% using a 721-A spectrophotometer. More significantly, the existence of melamine can be visually evaluated easily without the aid of any instrumentation.
Co-reporter:Zaifang Zhu, Ximin Zhou, Na Yan, Lei Zhou, Xingguo Chen
Journal of Chromatography A 2010 Volume 1217(Issue 11) pp:1856-1861
Publication Date(Web):12 March 2010
DOI:10.1016/j.chroma.2010.01.013
In order to improve the sensitivity of capillary electrophoresis (CE) and overcome the deficiency of commercial CE instruments in handling complex matrices directly, we proposed a novel technique which combined single-drop liquid–liquid–liquid microextraction (SD-LLLME) with CE on-line. In this technique, SD-LLLME was realized using a commercial CE instrument and, to further concentrate the target analyte, large-volume sample stacking combined sweeping without polarity switching was utilized. Even though without agitating the donor phase in the extraction process, the model compound, adenine was enriched 550-fold in only 10 min. The enrichment factors were 760 and 1030 when the extraction time was extended to 30 and 60 min, respectively. The relative standard deviations (RSDs) of adenine were 5.24% and 2.29% for peak area and migration time, respectively, which indicated that this method was much more reproducible compared to the existing methods that combined sample-preparation strategies with CE. In addition, this approach was selective while cleaning up target analyte. These mentioned advantages allowed the developed method to be an attractive approach to determining trace target compounds in complex real samples.
Co-reporter:Shao-Qiang Hu, Yong-Lei Chen, Hua-Dong Zhu, Hai-Jun Shi, Na Yan, Xing-Guo Chen
Journal of Chromatography A 2010 Volume 1217(Issue 34) pp:5529-5535
Publication Date(Web):20 August 2010
DOI:10.1016/j.chroma.2010.06.063
Eight l-tartrates and a d-tartrate with different alcohol moieties were used as chiral oils to prepare chiral microemulsions, which were utilized in conjunction with borate buffer to separate the enantiomers of β-blockers or structurally related compounds by the chiral microemulsion electrokinetic chromatography (MEEKC) method. Among them, six were found to have a relatively good chiral separation performance and their chiral recognition effect in terms of both enantioselectivity and resolution increases linearly with the number of carbon atoms in the alkyl group of alcohol moiety. The tartrates containing alkyl groups of different structures but the same number of carbon atoms, i.e. one of straight chain and one of branched chain, provide similar enantioseparations. The trend was elucidated according to the changes in the difference of the steric matching between the molecules of two enantiomers and chiral selector. Furthermore, it was demonstrated for the first time that a water insoluble solid compound, di-i-butyl l-tartrate (mp. 73.5 °C), can be used as an oil to prepare a stable microemulsion to be used in the chiral MEEKC successfully. And a critical effect of the microemulsion for chiral separation, which has never been reported before, was found in this experiment, namely providing a hydrophobic environment to strengthen the interactions between the chiral selector and enantiomers.
Co-reporter:Cuiling Ren, Jinhua Li, Jiefang Sun, Xingguo Chen, Zhide Hu, Desheng Xue
Journal of Luminescence 2010 Volume 130(Issue 1) pp:65-69
Publication Date(Web):January 2010
DOI:10.1016/j.jlumin.2009.07.019
In this paper, a new kind of fluorescent nanomaterial with morin modified alumina core and silica shell was prepared. Samples were characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), photoluminescent (PL) spectroscopy and fluorescence microscope. TEM results indicated that this material could be synthesized in nanometer range. PL spectra suggested that this new synthesized material was photostable and it showed nearly no dye leakage. This was because the dye molecules could form stable complex with the reactive aluminum cations on the surfaces of the alumina particles. The excitation and emission maxima of this new luminescent material were located at 420 and 493 nm, respectively. This new kind of luminescent nanomaterial was prepared by morin, AlCl3 and tetraethyl orthosilicate, which was very important for the large-scale and economic preparation luminescent nanoparticles because these precursors were inexpensive and the preparation process was convenient.
Co-reporter:Yang Hui, Lei Zhou, Xing-Guo Chen
Talanta 2010 Volume 80(Issue 5) pp:1619-1625
Publication Date(Web):15 March 2010
DOI:10.1016/j.talanta.2009.09.047
In this paper, a rapid and sensitive method for the determination of ammonia and 22 aliphatic amines derivatized was established by cyclodextrin (CD) modified micellar electrokinetic chromatography with laser-induced fluorescence detection using 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole as a derived reagent. By a series of unvaried studies, the best conditions were selected using 20 mM tetraborate (pH 9.70) containing 25 mM SDS, 7 mM β-CD, 10% acetonitrile, 0.5 M urea, and applied voltage 25 kV. Under the optimum conditions, ammonia and 22 aliphatic amines were separated successfully in 19 min. The signal response was linear over three-order of concentrations. The intra-day and inter-day relative standard deviations (RSD) were less than 0.81% and 1.00% for migration times, 1.76% and 2.01% for peak areas. Limits of detection (LOD) for the analytes was (S/N = 3) approximate 10−9–10−12 M. The method was applied to the determination of ammonia and aliphatic amines in environmental water with recoveries in the range of 90.2–110.8%. In addition, a quantitative structure–property relationship (QSPR) model for the estimation of the electrophoretic migration time was established with the comprehensive descriptors for structural and statistical analysis (CODESSA) program for the first time. The multilinear regression (MLR) equation contained two theoretical descriptors and had the following statistical indices: R2 = 0.9668, F = 290.7839, Rcv2=0.9576 and S2 = 0.8149.
Co-reporter:Hui-ge Zhang, Jin-hua Zhu, Sheng-da Qi, Na Yan and Xing-guo Chen
Analytical Chemistry 2009 Volume 81(Issue 21) pp:8886
Publication Date(Web):September 30, 2009
DOI:10.1021/ac901474j
In this report, a novel facile way of online preconcentration of trace levels of analytes in capillary electrophoresis is presented. The proposed strategy is based on the combination of strong acidic phosphate as sample buffers with borate separation buffer containing sodium dodecyl sulfate. When injection voltage is applied, the continuous introduction of low pH sample causes the apparent bulk flow inside the capillary gradually slows down. Finally at a certain point, it reaches the same magnitude as that of the oppositely migrating anionic micelles, thus the frontier of the micelle zone becomes stagnant. This steady state can be maintained for a very long time so that essentially extremely large volume of sample solutions can be injected into the capillary, and the cationic analytes may be efficiently stacked at the neutralized micelle zone. A theoretical model was proposed and preconcentration conditions of two model analytes, matrine and oxymatrine, were optimized with the aid of the model. Under optimized conditions, more than 1000-fold increase in sensitivity was obtained as compared with the normal hydrodynamic injection without sample stacking. The limits of detection for oxymatrine and matrine were 0.81 and 0.18 ng/mL, respectively, using photodiode array UV detection at wavelength 211 nm.
Co-reporter:Na Yan, Lei Zhou, Zaifang Zhu, Huige Zhang, Ximin Zhou, Xingguo Chen
Journal of Chromatography A 2009 Volume 1216(Issue 20) pp:4517-4523
Publication Date(Web):15 May 2009
DOI:10.1016/j.chroma.2009.03.042
In this work, a novel method combining constant pressure-assisted head-column field-amplified sample injection (PA-HC-FASI) with in-capillary derivatization was developed for enhancing the sensitivity of capillary electrophoresis. PA-HC-FASI uses an appropriate positive pressure to counterbalance the electroosmotic flow in the capillary column during electrokinetic injection, while taking advantage of the field amplification in the sample matrix and the water of the “head column”. Accordingly, the analytes were stacked at the stationary boundary between water and background electrolyte. After 600 s PA-HC-FASI, 4-fluoro-7-nitro-2,1,3-benzoxadiazole as derivatization reagent was injected, followed by an electrokinetic step (5 kV, 45 s) to enhance the mixing efficiency of analytes and reagent plugs. Standing a specified time of 10 min for derivatization reaction under 35 °C, then the capillary temperature was cooled to 25 °C and the derivatives were immediately separated and determined under 25 °C. By investigating the variables of the presented approach in detail, on-line preconcentration, derivatization and separation could be automatically operated in one run and required no modification of current CE commercial instrument. Moreover, the sensitivity enhancement factor of 520 and 800 together with the detection limits of 16.32 and 6.34 pg/mL was achieved for model compounds: glufosinate and aminomethylphosphonic acid, demonstrating the high detection sensitivity of the presented method.
Co-reporter:Shaoqiang Hu, Yonglei Chen, Huadong Zhu, Jinhua Zhu, Na Yan, Xingguo Chen
Journal of Chromatography A 2009 Volume 1216(Issue 45) pp:7932-7940
Publication Date(Web):6 November 2009
DOI:10.1016/j.chroma.2009.09.036
A novel procedure for in situ assembling a complex chiral selector, di-n-butyl l-tartrate–boric acid complex, by the reaction of di-n-butyl l-tartrate with boric acid in a running buffer was reported and its application in the enantioseparation of β-blockers and structural related compounds by chiral microemulsion electrokinetic chromatography (MEEKC) has been demonstrated. In order to achieve a good enantioseparation, the effect of dibutyl l-tartrate and sodium tetraborate concentration, surfactant identity and concentration, cosurfactant, buffer pH and composition, organic modifiers, as well as applied voltage and capillary length were investigated. Ten pairs of enantiomers that could not be separated with only dibutyl l-tartrate, obtained good chiral separation using the complex chiral selector; among them, seven pairs could be baseline resolved under optimized experimental conditions. The fixation of chiral centers by the formation of five-membered rings, and being oppositely charged with basic analytes were thought to be the key factors giving the complex chiral selector a superior chiral recognition capability. The effect of the molecular structure of analytes on enantioseparation was discussed in terms of molecular interaction.
Co-reporter:Yuanyuan Yue, Xingguo Chen, Jin Qin, Xiaojun Yao
Dyes and Pigments 2009 Volume 83(Issue 2) pp:148-154
Publication Date(Web):November 2009
DOI:10.1016/j.dyepig.2009.02.010
The binding characteristics of human serum albumin with C.I. Acid Green 1 were studied by employing fluorescence, resonance light scattering, ultraviolet–visible, circular dichroism, Fourier transform infrared techniques and molecular modeling. Spectroscopic analysis has revealed that quenching of human serum albumin by C.I. Acid Green operates by a static quenching mechanism. The results by Fourier transform infrared, circular dichroism and ultraviolet–visible absorption spectra experiment indicated that the secondary structures of protein were changed in the presence of C.I. Acid Green 1. Molecular modeling revealed that a dye–protein complex was stabilized by hydrophobic forces, Van-der-Waals force and hydrogen bonding, via amino acid residues. Furthermore, influences of coexisting substances on the binding constant of C.I. Acid Green 1-human serum albumin complexes were investigated.
Co-reporter:Na Yan, Zaifang Zhu, Ning Ding, Lei Zhou, Yalei Dong, Xingguo Chen
Journal of Chromatography A 2009 Volume 1216(Issue 49) pp:8665-8670
Publication Date(Web):4 December 2009
DOI:10.1016/j.chroma.2009.10.027
Transient isotachophoresis (tITP) can improve the sensitivity of capillary electrophoresis (CE). In general, it was carried out under the condition of suppressed electroosmotic flow (EOF). However, some special conditions, such as extreme low pH background electrolyte and coating were needed to achieve the requirements of suppressed EOF. In this work, an approach of tITP under the strong counter-EOF in open system (counter-EOF-tITP) is presented for the rapid and sensitive preconcentrating the reduced glutathione (GSH) and the oxidized glutathione (GSSG) without modifying the capillary and the commercial CE instrument. The parameters of the experimental system, such as the concentration of leading electrolyte, the injected amount of terminating electrolyte and the injected pressure of sample were investigated in detail to understand the mechanism of counter-EOF-tITP. The sensitivity enhancement factors were of 320 for GSH and 280 for GSSG. In addition, the detection limit of 23.4 and 18.0 μg L−1 for GSH and GSSG was achieved, respectively. The method's applicability was demonstrated by determining GSH and GSSG in tomato and human serum.
Co-reporter:Zai-fang Zhu;Na Yan;Ximin Zhou;Lei Zhou ;Xingguo Chen
Journal of Separation Science 2009 Volume 32( Issue 20) pp:3481-3488
Publication Date(Web):
DOI:10.1002/jssc.200900294
Abstract
In this work, we overcame the deficiencies of large volume sample stacking (LVSS) in separating low-mobility and neutral analytes through combining LVSS with sweeping in CE, and employed this new approach to enrich and separate neutral and anionic analytes simultaneously. This technique was carried out with pressure injection of large-volume sample followed by EOF as a pump pushing the bulk of low-conductivity sample matrix out of the outlet of the capillary while analytes were swept by micelles and separated via MEKC without the electrode polarity switching. Careful optimization of the enrichment and separation conditions allowed the enrichment factors (EFs) of peak height and peak area of the analytes to be in the range of 9–33 and 21–35 comparing with the conventional injection mode, respectively. The five analytes were baseline separated in 15 min and the detection limits ranged from 26.5 to 55.8 ng/mL (S/N = 3). The developed method was successfully applied to determine adenine, caffeine, theophylline, reduced L-glutathione (GSH) and oxidized L-glutathione (GSSG) in two different teas with recoveries that ranged from 84.4 to 105.2%.
Co-reporter:Na Yan, Lei Zhou, Zaifang Zhu and Xingguo Chen
Journal of Agricultural and Food Chemistry 2009 Volume 57(Issue 3) pp:807-811
Publication Date(Web):January 21, 2009
DOI:10.1021/jf803429e
This paper describes an approach to determine melamine (MEL) in liquid milk, yogurt, whole milk powder, fish feed, and fish at residue levels using capillary zone electrophoresis with diode array detection (CZE-DAD) for the first time. Suspicious samples were extracted with 1% trichloroacetic acid while 1 mL of chloroform was used to precipitate fat in the real samples. After centrifuging and filtering, the extract was analyzed by CZE-DAD directly. By investigating the variables of extraction, separation, and detection in detail, the entire analytical procedure including sample preparation could be completed within 30 min. The limits of detection and quantitation for MEL were found to be 0.01 and 0.05 μg mL−1, respectively. The proposed method was successfully applied for the analysis of MEL in dairy products, fish feed, and fish with total recoveries ranging from 93 to 104%.
Co-reporter:Yuanyuan Yue, Xingguo Chen, Jin Qin, Xiaojun Yao
Colloids and Surfaces B: Biointerfaces 2009 Volume 69(Issue 1) pp:51-57
Publication Date(Web):15 February 2009
DOI:10.1016/j.colsurfb.2008.10.016
This study was designed to examine the interaction of oxaliplatin with human serum albumin (HSA) under physiological conditions by using fluorescence, absorption, FT-IR and circular dichroism (CD) spectroscopic techniques in combination with molecular docking study. Spectroscopic analysis of the emission quenching at different temperatures has revealed that the quenching mechanism of oxaliplatin with HSA was static quenching mechanism. The value of 1.64 nm for the distance r between the donor (HSA) and acceptor (oxaliplatin) was derived from the fluorescence resonance energy transfer. From the CD and FT-IR results, it was apparent that the interaction of oxaliplatin with HSA caused a conformational change of the protein. Molecular docking study showed that oxaliplatin bind to residues located in subdomain IIA of HSA. The effect of metal ions and amino acids on the binding constant of HSA–oxaliplatin complex was also discussed.
Co-reporter:Yuanyuan Yue, Xingguo Chen, Jin Qin, Xiaojun Yao
Colloids and Surfaces B: Biointerfaces 2009 Volume 72(Issue 2) pp:313
Publication Date(Web):1 September 2009
DOI:10.1016/j.colsurfb.2009.04.005
Co-reporter:Xiumei Liu, Shuyan Li, Jingshu Zhang, Xingguo Chen
Journal of Chromatography B 2009 Volume 877(Issue 27) pp:3144-3150
Publication Date(Web):1 October 2009
DOI:10.1016/j.jchromb.2009.08.002
In this paper, a fast method for the study on the interactions of a series of drugs used in the treatment of hypertension with human serum albumin (HSA) by flow injection-capillary electrophoresis (FI-CE) was developed based on the principle of frontal analysis (FA). The binding parameters were determined by FI-CE-FA from Scatchard equation and compared with results obtained by non-CE methods and literature values. A multiple linear regression (MLR) model between the drug–protein binding constants (K) and structural descriptors of drugs was constructed. L-tryptophan (L-try) and phenylbutazone (PB) were used as displacement reagents to investigate the binding sites of a series of drugs on HSA. The binding synergism effect between drugs and the effects of many metal ions existing in human plasma on protein binding were also investigated systematically.
Co-reporter:Yuanyuan Yue, Xingguo Chen, Jin Qin, Xiaojun Yao
Journal of Pharmaceutical and Biomedical Analysis 2009 49(3) pp: 753-759
Publication Date(Web):
DOI:10.1016/j.jpba.2008.12.017
Co-reporter:Jinhua Zhu, Shengda Qi, Jinhua Li, Xingguo Chen
Journal of Chromatography A 2008 Volume 1212(1–2) pp:137-144
Publication Date(Web):28 November 2008
DOI:10.1016/j.chroma.2008.10.027
Two stacking methods in micellar electrokinetic chromatography (MEKC) were investigated in this article in an attempt to increase the amount of sample injected, as well as to focus analytes onto a small zone. One employed a “high-conductivity zone”, which was inserted between the sample zone and background solution to build an unequal conductivity gradient. The other employed a “low-temperature bath”. A portion of the capillary was immersed in a low-temperature bath, which served as a “pseudo-low-conductivity zone”. As a result, a large volume of sample injection can be achieved. Using three phenolic acids-chlorogenic acid (CGA), caffeic acid (CA) and ferulic acid (FA) in coffee as model compounds, the limit of detection (LoD) was determined to be 0.31 μg/ml (S/N = 3) for CGA by means of normal MEKC under suppressed electroosmotic flow (EOF). The LoD could be improved to 2.8 × 10−2, 5.3 × 10−3 and 6.0 × 10−3 μg/ml, respectively, when normal MEKC-stacking, high-conductivity zone MEKC-stacking and the low-temperature zone MEKC-stacking methods were applied. Furthermore, the high conductivity zone and the low-temperature bath were operated simultaneously on one capillary to investigate the synergism effect. The results showed that there did exist synergism effect for CGA and CA when the two were hyphenated. The stacking efficiency was higher than that of the single one used. However, there was not synergism effect for FA.
Co-reporter:Jinhua Zhu, Shengda Qi, Huige Zhang, Xingguo Chen, Zhide Hu
Journal of Chromatography A 2008 Volume 1192(Issue 2) pp:319-322
Publication Date(Web):30 May 2008
DOI:10.1016/j.chroma.2008.04.005
Two on-line sample concentration techniques, sample stacking and sweeping under pH-suppressed electroosmotic flow, were evaluated in microemulsion electrokinetic chromatography. The concept of stacking with anion selective electrokinetic injection and a water plug in a reverse-migrating microemulsion (SASIW-RMME) was brought forward in this article. Six flavonoids were concentrated using a microemulsion consisting of 80 mM sodium dodecyl sulfate, 1.2% (v/v) ethyl acetate, 0.6% (v/v) 1-butanol, 10% acetonitrile (v/v) and 50 mM phosphoric acid (pH* 1.8). Significant detector response improvements were achieved. The limits of detection were in the low ng/ml level. Finally, the sample of Fructus aurantii Immaturus was analyzed using sweeping technique.
Co-reporter:Yuanyuan Yue, Xingguo Chen, Jin Qin, Xiaojun Yao
Dyes and Pigments 2008 Volume 79(Issue 2) pp:176-182
Publication Date(Web):November 2008
DOI:10.1016/j.dyepig.2008.02.008
The mechanism of interaction between C.I. Direct Yellow 9 and human serum albumin was studied using spectroscopic methods including fluorescence spectra, UV–vis, Fourier transform infrared (FT-IR) and circular dichroism (CD). The quenching mechanism was investigated in terms of the association constants, number of binding sites and basic thermodynamic parameters. The distance between the human serum albumin donor and the acceptor dye was 3.64 nm as derived from fluorescence resonance energy transfer. Alteration of the secondary protein structure in the presence of the dye was confirmed by UV, FT-IR and CD spectroscopy. Molecular modeling revealed that a dye–protein complex was stabilized by hydrophobic forces and hydrogen bonding, via amino acid residues.
Co-reporter:Yuanyuan Yue, Yaheng Zhang, Ying Li, Jinhua Zhu, Jin Qin, Xingguo Chen
Journal of Luminescence 2008 Volume 128(Issue 3) pp:513-520
Publication Date(Web):March 2008
DOI:10.1016/j.jlumin.2007.09.029
The binding of nobiletin to human serum albumin (HSA) was investigated by fluorescence, UV–vis, FT-IR, CD, and molecular modeling. Fluorescence data revealed the presence of a single class of binding site on HSA and its binding constants (K) at four different temperatures (289, 296, 303 and 310 K) were 4.054, 4.769, 5.646 and 7.044×104 M−1, respectively. The enthalpy change (ΔH0) and the entropy changes (ΔS0) were calculated to be 1.938 kJ mol−1 and 155.195 J mol−1 K−1 according to the Van’t Hoff equation. The binding average distance, r, between the donor (HSA) and the acceptor (nobiletin) was evaluated and found to be 2.33 nm according to the Förster's theory of non-radiation energy transfer. Changes in the CD and FT-IR spectra were observed upon ligand binding along with a significant degree of tryptophan fluorescence quenching on complex formation. Computational mapping of the possible binding sites of nobiletin revealed the molecule to be bound in the large hydrophobic cavity of subdomain IIA.
Co-reporter:Yaheng Zhang, Jiazhong Li, Lijun Dong, Ying Li, Xingguo Chen
Journal of Molecular Structure 2008 Volume 889(1–3) pp:119-128
Publication Date(Web):29 October 2008
DOI:10.1016/j.molstruc.2008.01.040
In this study the interaction between esculin and human serum albumin (HSA) in AOT/isooctane/water microemulsions was studied for the first time using fluorescence quenching technique in combination with UV absorption spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD) spectroscopy and dynamic light scattering (DLS) technique. Fluorescence data in ωo 20 microemulsions revealed the presence of the binding site of esculin on HSA and its binding constants at four different temperatures were obtained. The affinities in microemulsions are similar to that in buffer solution. The alterations of protein secondary structure in the microemulsions in the absence and presence of esculin compared with the free form of HSA in buffer were qualitatively and quantitatively analyzed by the evidence from CD and FT-IR spectroscopes. The displacement experiments confirmed that esculin could bind to the site I of HSA, which was in agreement with the result of the molecular modeling study. Furthermore, the DLS data suggested that HSA may locate at the interface of the microemulsion and esculin could interact with them.
Co-reporter:Yaheng Zhang, Ying Li, Lijun Dong, Jiazhong Li, Wenying He, Xingguo Chen, Zhide Hu
Journal of Molecular Structure 2008 Volume 875(1–3) pp:1-8
Publication Date(Web):17 March 2008
DOI:10.1016/j.molstruc.2007.03.063
The interaction between naringin and human serum albumin (HSA) has been thoroughly studied by fluorescence quenching technique in combination with UV absorption spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD) spectroscopy and molecular modeling method. Under the simulative physiological conditions, fluorescence data revealed the presence of the binding site on HSA and its binding constants (K) are 1.62 × 104, 1.68 × 104, 1.72 × 104, and 1.79 × 104 M−1 at 289, 296, 303, and 310 K, respectively. The alterations of protein secondary structure in the presence of naringin aqueous solution were qualitative and quantitative calculated by the evidence from CD and FT-IR spectroscopes. In addition, according to the Van’t Hoff equation, the thermodynamic functions standard enthalpy (ΔH0) and standard entropy (ΔS0) for the reaction were calculated to be 3.45 kJ mol−1 and 92.52 J mol−1 K−1. These results indicated that naringin binds to HSA mainly by a hydrophobic interaction. Furthermore, the displacement experiments confirmed that naringin could bind to the site I of HSA, which was also in agreement with the result of the molecular modeling study.
Co-reporter:Yaheng Zhang, Lijun Dong, Jiazhong Li, Xingguo Chen
Talanta 2008 Volume 76(Issue 2) pp:246-253
Publication Date(Web):15 July 2008
DOI:10.1016/j.talanta.2008.02.033
In this study the interaction between gallic acid and human serum albumin (HSA) in AOT/isooctane/water microemulsions was characterized for the first time using fluorescence quenching technique in combination with UV absorption spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD) spectroscopy and dynamic light scattering (DLS) technique. In water–surfactant molar ratio (ωo) = 20 microemulsions fluorescence data revealed the presence of one binding site of gallic acid on HSA and its binding constants (K) were (1.18 ± 0.02) × 104, (1.13 ± 0.02) × 104, (1.03 ± 0.02) × 104, (0.95 ± 0.02) × 104, (0.87 ± 0.02) × 104 and (0.82 ± 0.03) × 104 M−1 at 282, 289, 296, 303, 310 and 317 K, respectively. The affinities in microemulsions were much higher than that in buffer solution. FT-IR and CD data suggested that the protein conformations were altered with the reductions of α-helices from 54–56% for free HSA in buffer to 40–41% for free HSA in microemulsion. After binding with gallic acid, the α-helices of HSA in microemulsion increased 2–7% for different drug–protein molar ratio. The thermodynamic functions standard enthalpy (ΔH0) and standard entropy (ΔS0) for the reaction were calculated to be −8.10 kJ mol−1 and 49.42 J mol−1 K−1. These results indicated that gallic acid bound to HSA mainly by hydrophobic interaction and electrostatic interaction in microemulsions. In addition, the displacement experiments confirmed that gallic acid could bind to the site I of HSA, which was approved by the molecular modeling study. Furthermore, the DLS data suggested that HSA may locate at the interface of the microemulsion and gallic acid could interact with them.
Co-reporter:Jiefang Sun;Lihong Liu;Cuiling Ren;Xingguo Chen;Zhide Hu
Microchimica Acta 2008 Volume 163( Issue 3-4) pp:271-276
Publication Date(Web):2008 October
DOI:10.1007/s00604-008-0007-4
A novel CdSe quantum dots-based technology platform was established in aqueous solution. It can perform accurate and simple determination of vitamin B1 concentration in pharmaceutical samples with satisfactory results. Under optimum conditions, this method demonstrates high sensitivity and selectivity. A linear relationship was observed between 5.00 and 40.0 μg ml−1 with a correlation coefficient of 0.9963 for vitamin B1 determination and a detection limit of 70 ng ml−1. The citrate-protected CdSe quantum dots showing temperature-sensitive luminescence intensity variation and spectral shift at moderate temperature.
Co-reporter:Yaheng Zhang;Lijun Dong;Ying Li;Jiazhong Li;Xingguo Chen
Journal of Fluorescence 2008 Volume 18( Issue 3-4) pp:661-670
Publication Date(Web):2008 July
DOI:10.1007/s10895-008-0347-9
The interaction between bergenin and human serum albumin (HSA) in AOT/isooctane/water microemulsions was studied by fluorescence quenching technique in combination with UV absorption spectroscopy, circular dichroism (CD) spectroscopy and dynamic light scattering (DLS) technique. Fluorescence data in ωo 20 microemulsions revealed the presence of a binding site of bergenin on HSA and its binding constants (K) were 1.64 × 104, 1.44 × 104, 1.26 × 104 and 1.09 × 104 M−1 at 289, 296, 303, and 310 K, respectively. The binding of bergenin with HSA in microemulsions was stronger than that in buffer solution. The alterations of protein secondary structure in the microemulsions in the absence and presence of bergenin compared with the free form of HSA in buffer were qualitatively and quantitatively analyzed by the evidence from CD spectra. Enthalpy and entropy changes for the reaction were calculated to be −14.45 kJ mol−1 and 30.76 J mol−1 K−1. These results indicated that bergenin bound to HSA mainly by a hydrophobic interaction in microemulsions which was in agreement with the result of the molecular modeling study. The DLS data suggested that HSA may locate at the interface of the microemulsion and bergenin could interact with them.
Co-reporter:Cuiling Ren;Jinhua Li;Qian Liu;Juan Ren;Xingguo Chen
Nanoscale Research Letters 2008 Volume 3( Issue 12) pp:
Publication Date(Web):2008 December
DOI:10.1007/s11671-008-9186-5
A new method for preparing magnetic iron oxide nanoparticles coated by organic dye-doped silica shell was developed in this article. Iron oxide nanoparticles were first coated with dye-impregnated silica shell by the hydrolysis of hexadecyltrimethoxysilane (HTMOS) which produced a hydrophobic core for the entrapment of organic dye molecules. Then, the particles were coated with a hydrophilic shell by the hydrolysis of tetraethylorthosilicate (TEOS), which enabled water dispersal of the resulting nanoparticles. The final product was characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, photoluminescence spectroscopy, and vibration sample magnetometer. All the characterization results proved the final samples possessed magnetic and fluorescent properties simultaneously. And this new multifunctional nanomaterial possessed high photostability and minimal dye leakage.
Co-reporter:Jinhua Zhu, Kai Yu, Xingguo Chen, Zhide Hu
Journal of Chromatography A 2007 Volume 1166(1–2) pp:191-200
Publication Date(Web):28 September 2007
DOI:10.1016/j.chroma.2007.08.018
Two on-column preconcentration techniques named stacking with reverse migrating micelles (SRMM) and anion selective electrokinetic injection and a water plug-sweeping with reverse migrating micelles (ASIW–sweep–RMM) were used and compared for concentration and separation of flavonoids in Chinese herbs using reverse migration micellar electrokinetic chromatography (RM-MEKC). The optimal background electrolyte (BGE) used for separation and preconcentration was a solution composed of 20 mM phosphoric acid (H3PO4)–100 mM sodium dodecyl sulfate (SDS)–20% (v/v) acetonitrile (ACN) buffer (pH 2.0), the applied voltage was −15 kV. To achieve reasonable results of the two techniques, the conditions which affected preconcentration were examined. A comparison of used techniques with normal hydrodynamic injection (5 s), concerning enhancement factors and limits of detection (LODs) was presented. Under the optimum stacking conditions, about 27–37- and 45–194-fold improvement in the detection sensitivity was obtained for SRMM and ASIW–sweep–RMM, respectively, compared to usual hydrodynamic sample injection (5 s). The LODs (S/N = 3) for SRMM and ASIW–sweep–RMM in terms of peak height, can reach down to 1.15 × 10−2 μg/ml for hesperetin and 2.4 × 10−3 μg/ml for nobiletin, respectively. Finally, the amounts of the six flavonoids in extract of Fructus aurantii Immaturus were successfully determined using ASIW–sweep–RMM. The six analytes were baseline separated with sample matrix under the optimum ASIW–sweep–RMM conditions and the experimental results showed that preconcentration was well achieved after the dilution of sample solutions.
Co-reporter:Lijun Dong, Xingguo Chen, Zhide Hu
Journal of Luminescence 2007 Volume 124(Issue 1) pp:85-92
Publication Date(Web):May 2007
DOI:10.1016/j.jlumin.2006.02.002
The determination of proteins with 2-(4-chloro-2-phosphonophenylazo)-7-(4-iodophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid (CPA-pI) by Rayleigh light scattering (RLS) was studied in this paper. The weak RLS of CPA-pI and BSA can be enhanced greatly by the addition of Al3+ at the pH 5.6 and an enhanced RLS signal was produced at 365–385 nm. Based on the reaction of CPA-pI, Al3+ and proteins, a new quantitative determination method for proteins has been developed. The effect of three variables for the determination of proteins was optimized by means of artificial neural networks (ANNs) using extended delta-bar-delta (EDBD) algorithms with the optimal network structure of 3-5-1. This method is very sensitive (2.5–35.4 μg/ml for bovine serum albumin (BSA)), rapid (<2 min), simple (one step) and tolerance of most interfering substances. Six samples of protein in human serum were determined and the maximum relative error is no more than 2% and the recovery is between 95% and 105%.
Co-reporter:Lijun Dong;Ying Li;Yaheng Zhang;Xingguo Chen;Zhide Hu
Microchimica Acta 2007 Volume 159( Issue 1-2) pp:49-55
Publication Date(Web):2007 June
DOI:10.1007/s00604-006-0714-7
A flow injection method combined with Resonance light scattering detection was developed for the determination of protein concentration in human serum samples. This method is based on the enhanced RLS signals of protein binding with the dye acid chrome blue K. The enhanced RLS intensities at 264 nm, in an acidic aqueous solution, were proportional to the protein concentration over the range of 2.0–40.0 µg·mL−1 for human serum albumin (HSA) and the limit of detection (3σ) is 85 ng·mL−1. This method was successfully applied to the quantification of total proteins in human serum samples. The maximum relative standard deviation is less than 2% and the recovery is between 97 and 103% for the standard addition method. The sample throughput was 60 h−1.
Co-reporter:Lihong Liu;Xingguo Chen;Zhide Hu
Microchimica Acta 2007 Volume 159( Issue 1-2) pp:125-131
Publication Date(Web):2007 June
DOI:10.1007/s00604-007-0738-7
A simple, sensitive and continuous on-line stacking technique using head-column (HC)-field amplified sample injection (FASI) and sweeping was developed by combination of flow injection with micellar electrokinetic chromatography. Berberine, palmatine and jatrorrhizine were selected as model mixture to demonstrate this stacking method. Based on the characteristic of a 16-way injection valve (16-V), a sample was injected electrokinetically into a capillary after the introduction of a plug of water. Under optimum conditions, 64–86-fold improvement in the detection sensitivity was obtained for the analytes and the sample throughput can reach up to 24 h−1 using the background electrolyte containing 240 mM ammonium acetate (pH 4.7), 30% (v/v) ethanol, and 2% (v/v) polyoxyethylene sorbitan monolaurate (Tween 20). The repeatabilities (n = 4) reached relative standard deviation values of 1.2, 2.7 and 3.1% for the peak areas and 1.6, 3.3 and 3.8% for peak heights of berberine, palmatine and jatrorrhizine, respectively. The limit of detection for the berberine, palmatine and jatrorrhizine was found to be 27, 26, 22 ng mL−1 (S/N = 3).
Co-reporter:Lihong Liu, Xingguo Chen, Zhide Hu
Talanta 2007 Volume 71(Issue 1) pp:155-159
Publication Date(Web):15 January 2007
DOI:10.1016/j.talanta.2006.03.032
A simple, rapid, and accurate method for the separation and determination of alpinetin and cardamonin in Alpinia katsumadai Hayata was developed by combination of flow injection (FI)–micellar electrokinetic chromatography (MEKC) for the first time. The analysis was carried out using an unmodified fused-silica capillary (50 μm i.d.; total length 13.6 cm; effective length 10.3 cm) and direct ultraviolet (UV) detection at 214 nm. The sample throughput was 11–24 samples per hour using the background electrolyte (BGE) containing 4 mM sodium borate–8 mM NaH2PO4 (pH 8.1)–8 mM sodium dodecyl sulfate (SDS)–19% (v/v) ethanol. The repeatabilities (n = 4) reached relative standard deviation values (R.S.D.) of 3.0% and 2.5% for the peak areas and 2.5% and 3.1% for peak heights of alpinetin and cardamonin, respectively. Regression equations revealed linear relationships (r2: 0.9993–0.9994) between the peak area of each analyte and the concentration. Recoveries were in the range 90–92% and 99–105% for alpinetin and cardamonin, respectively.
Co-reporter:Xiumei Liu, Jingshu Zhang, Xingguo Chen
Journal of Chromatography B 2007 Volume 852(1–2) pp:325-332
Publication Date(Web):1 June 2007
DOI:10.1016/j.jchromb.2007.01.034
A sensitive and reproducible method was developed for the separation and determination of three water-soluble components—protocatechuic aldehyde (PAH), β-(3,4-dihydroxyphenyl) lactic acid (DSS) and protocatechuic acid (PA) in medicine plant Salvia miltiorrhiza Bunge and two related traditional medicinal preparations using flow injection-capillary electrophoresis system. This analysis was carried out by using an unmodified fused-silica capillary (28.4 cm × 75 μm i.d. × 375 μm o.d., 25 cm effective separation length) and direct ultraviolet detection at 214 nm, 7.0 kV applied voltage. With boric acid (200 mM) adjusted to pH 7.8 as a background electrolyte. The separation was achieved in 9 min. The sample throughput rate could reach up to 15 h−1. Calibration curves showed good linearity with correlation coefficients (r) more than 0.9986. The repeatability (defined as R.S.D.) were 0.20%, 0.46%, 0.47% with migration time evaluation and 0.62%, 3.66%, 1.50% with peak area evaluation for PAH, DSS and PA, respectively. The limits of detection (S/N = 3) were 0.36 μg/mL, 0.84 μg/mL, and 0.73 μg/mL for PAH, DSS, and PA, respectively. The mean recoveries of PAH, DSS and PA were 103.2%, 98.1% and 100.5%, respectively. This method has been applied successfully to monitor these three components in Salvia miltiorrhiza Bunge and its two traditional medicinal preparations.
Co-reporter:Kan Tian, Yushang Wang, Yonglei Chen, Xingguo Chen, Zhide Hu
Talanta 2007 Volume 72(Issue 2) pp:587-593
Publication Date(Web):30 April 2007
DOI:10.1016/j.talanta.2006.11.027
A capillary zone electrophoresis method using only 1-alkyl-3-methylimidazolium-based ionic liquids as background electrolyte for the simultaneous determination of five anthraquinone derivatives including aloe-emodin, emodin, chrysophanol, physcion and rhein in Rhubarb species was described. Ion association constants, Kass, between anthraquinone anions and imidazolium cations were determined by analyzing the electrophoretic mobility change of anthraquinone anions using a non-linear least-squares method and factors contributing to ion associability were systematically clarified. For method optimization, several parameters such as ionic liquids concentration, background electrolyte pH and applied voltage, on the separation were evaluated and the optimum conditions were obtained as follows: 90 mM 1-butyl-3-methylimidazolium tetrafluoroborate (pH 11.0) with an applied voltage of 20 kV. Under these conditions, the method has been successfully applied to the determination of anthraquinones in extracts of two kinds of Rhubarb plants (R. palmatum and R. hotaoense) within 12 min. The method proposed herein was shown to be much simpler than the previously reported methods.
Co-reporter:Lijun Dong, Xingguo Chen, Zhide Hu
Talanta 2007 Volume 71(Issue 2) pp:555-560
Publication Date(Web):15 February 2007
DOI:10.1016/j.talanta.2006.04.026
Co-reporter:Kan Tian, Hongli Chen, Jianghong Tang, Xingguo Chen, Zhide Hu
Journal of Chromatography A 2006 Volume 1132(1–2) pp:333-336
Publication Date(Web):3 November 2006
DOI:10.1016/j.chroma.2006.08.090
The enantioseparation of four stereoisomers of palonosetron hydrochloride by micellar electrokinetic chromatography using sodium cholate as chiral surfactant was described. Sodium cholate was shown to be effective in separating palonosetron hydrochloride stereoisomers. For method optimization, several parameters such as sodium cholate concentration, buffer pH and concentration, the types and concentration of organic modifiers and applied voltage, on the enantioseparation were evaluated and the optimum conditions were obtained as follows: 30 mM borate buffer (pH 9.40) containing 70 mM sodium cholate and 20% (v/v) methanol with an applied voltage of 20 kV. Under these conditions, baseline separation of palonosetron hydrochloride stereoisomers was achieved within 18 min.
Co-reporter:Huige Zhang, Kan Tian, Jianghong Tang, Shengda Qi, Hongli Chen, Xingguo Chen, Zhide Hu
Journal of Chromatography A 2006 Volume 1129(Issue 2) pp:304-307
Publication Date(Web):6 October 2006
DOI:10.1016/j.chroma.2006.08.016
Microemulsion electrokinetic chromatography (MEEKC) using 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4) ionic liquid (IL) as additive was developed for the analysis of baicalin, wogonin and baicalein in Scutellariae radix and its preparation. After conducting a series of optimizations, baseline separation was obtained for the analytes within 5 min under the optimum conditions (sodium dodecyl sulfate (SDS) 0.88% (m/v) ethyl acetate 0.8% (v/v) butan-1-ol 0.2% (v/v) and the buffer composition were 25% acetonitrile (v/v), 7.5 mM BMIM-BF4 and 10 mM NaH2PO4, pH 8.2, applied voltage 17.5 kV and detection at 254 nm), the method has been successfully applied to the determination and quantification of the analytes in the extracts of S. radix (cooked), S. radix (raw) and Qingfeiyihuowan which was the preparation including S. radix.
Co-reporter:Kan Tian, Huige Zhang, Xingguo Chen, Zhide Hu
Journal of Chromatography A 2006 Volume 1123(Issue 1) pp:134-137
Publication Date(Web):4 August 2006
DOI:10.1016/j.chroma.2006.04.021
A simple and rapid method for the simultaneous determination of five anthraquinone derivatives including aloe-emodin, emodin, chrysophanol, physcoin and rhein in Rheum species and Polygonum cuspidatum was established by capillary zone electrophoresis (CZE) using β-cyclodextrin (CD) as modifier and urea to enhance its solubility. The apparent binding constants of these derivatives with β-CD were evaluated. After an optimization study, the best conditions were selected using 35 mM phosphate buffer (pH 11.0) containing 20 mM β-CD and 2 M urea, applied voltage 20 kV and detection at 254 nm. Under such conditions, all of the five anthraquinones were baseline-separated within a short analysis time of 12 min with symmetrical peaks and high theoretical plate numbers (189 000–314 000). The RSD values of the migration times and peak areas were 0.6–1.1, 1.3–1.9% (intra-day) and 0.6–1.5, 1.3–2.8% (inter-day, for a 5-day period), respectively. The limits of detection for the analytes (S/N = 3) were 0.33–0.62 μg/ml. The recoveries were ranged from 93.37 to 107.69%. The proposed method was successfully applied to the determination of anthraquinones in ethanol extracts of two kinds of Rheum plants (R. palmatum and R. hotaoense) and P. cuspidatum.
Co-reporter:Shengda Qi, Yuqin Li, Yanru Deng, Yuqiao Cheng, Xingguo Chen, Zhide Hu
Journal of Chromatography A 2006 Volume 1109(Issue 2) pp:300-306
Publication Date(Web):24 March 2006
DOI:10.1016/j.chroma.2006.01.045
In this paper, novel capillary electrophoresis (CE) methods, which used ionic liquids (1-ethyl-3-methylimidazoium tetrafluoroborate, 1-butyl-3-methylimidazoium tetrafluoroborate), were established to separate and determine some bioactive flavone derivatives in Chinese herb Seriphidium santolinum (Schrenk) Poljak. In order to investigate the traits of ionic liquids in CE, borate was also used as electrolyte to compare with. And the excellence of CE, which used ionic liquids as main running electrolyte and β-cyclodextrin (β-CD) as modifier, was illuminated as well. As a result of the study, the difference of ionic liquids and borate in CE was discussed and the advantage of CE, which used ionic liquids as electrolytes for separation, was shown. The analysis was obtained within short time (5–6 min). From the result, it was found that the system, which used ionic liquids, was robust because the joule heating was small. The method of CE, which used ionic liquids, has lower detection limits (0.137–0.642 μg/mL) than that of borate (0.762–1.036 μg/mL). And the CE, which used ionic liquids method, has lower limit of linear range (1.100–2.656 μg/mL), while that of CE, which used borate method, was 2.188–5.313 μg/mL.
Co-reporter:Xingguo Chen;Yang Hui;Yonglei Chen;Zhide Hu;Hongli Chen;Yuming Dong
Journal of Separation Science 2006 Volume 29(Issue 13) pp:2049-2055
Publication Date(Web):28 JUL 2006
DOI:10.1002/jssc.200600073
A micellar electrokinetic capillary chromatography method with laser-induced fluorescence detection was developed for the analysis of epinephrine and dopamine after derivatization with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole. The optimum derivatization conditions were: 30 mM sodium borate (pH adjusted to 8.0 with 1.0 M HCl), reaction time 30 min at 60°C. Baseline separation was achieved within 14 min with a running buffer composed of 10 mM sodium borate + 25 mM sodium dodecyl sulfate (pH adjusted to 9.5 with 0.1 M NaOH) and an applied voltage of 15 kV. Good linearity relationships (correlation coefficients: 0.9991 for epinephrine and 0.9985 for dopamine) between peak areas and concentrations of the analytes were obtained. The detection limits and quantification limits for epinephrine and dopamine were 0.0038 mg/L and 0.013 mg/L, and 0.065 mg/L and 0.020 mg/L, respectively. The method was applied to the analysis of the two compounds in two Chinese medicines with recoveries in the range of 92.6–108.7%.
Co-reporter:Shengda Qi, Lan Ding, Kan Tian, Xingguo Chen, Zhide Hu
Journal of Pharmaceutical and Biomedical Analysis 2006 Volume 40(Issue 1) pp:35-41
Publication Date(Web):23 January 2006
DOI:10.1016/j.jpba.2005.06.003
Three bioactive triterpenes ursolic acid, oleanolic acid and 2α,3β,24-trihydroxy-urs-12-en-28-oic acid were simultaneously separated by nonaqueous capillary electrophoresis (NACE) with methanol:acetonitrile (65:35 v/v) mixture containing 90 mm trishydroxymethylaminomethane (Tris) at an applied voltage of +25 kV and a hydrodynamic injection of 5 s. The effect of solvent composition, electrolyte nature and concentration on the electrophoretic behavior of the analytes were systematically studied. Separations were carried out in a fused-silica capillary tube with UV detection at 214 nm. Good separation and correlation coefficients were obtained. Meanwhile, the method was applied to separation and determination the three components in six Chinese herbs extraction. It is concluded that this method could be used for speedy and accurate qualitative and quantitative analysis of bioactive triterpenes in Chinese herbs.
Co-reporter:Kan Tian, Shengda Qi, Yuqiao Cheng, Xingguo Chen, Zhide Hu
Journal of Chromatography A 2005 Volume 1078(1–2) pp:181-187
Publication Date(Web):17 June 2005
DOI:10.1016/j.chroma.2005.05.018
In this paper, a micellar electrokinetic chromatographic (MEKC) method using ionic liquid as modifier for the quantification of the active components of lignans found in the medicinal herbs Schisandra species was developed for the first time. Preliminary investigations employing sodium dodecyl sulfate (SDS) as surfactant did not lead to the necessary resolution of the studied compounds, the addition of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4) to the SDS micellar system resulted in the complete separation of all the compounds. The effects on the separation by several parameters such as BMIM-BF4 and SDS concentration, applied voltage, background electrolyte pH and concentration, were evaluated. Under the optimal conditions (5 mM borate-5 mM phosphate buffer in the presence of 20 mM SDS and 10 mM BMIM-BF4, pH 9.2, applied voltage 25 kV and detection at 254 nm), the method successfully applied to the determination of lignans in extracts of Schisandra chinensis (Turcz.) Baill. and Schisandra henryi C.B. Clarke in less than 13 min. The separation mechanism was also discussed.
Co-reporter:Shengda Qi;Yuqin Li;Shuixian Wu;Xingguo Chen;Zhide Hu
Journal of Separation Science 2005 Volume 28(Issue 16) pp:2180-2186
Publication Date(Web):25 OCT 2005
DOI:10.1002/jssc.200500134
Nonaqueous CE (NACE) coupled to UV detection is described for the separation and determination of bioactive flavone derivatives in Chinese herbs extraction. After optimization of electrophoresis parameters, including the electrolyte nature and the organic solvent composition, a reliable separation of the analytes in an ACN/methanol (60 : 40, v/v) mixture containing 80 mM Tris and 10 mM sodium cholate was performed. The detection was performed at 254 nm. Method performances, including migration time and peak area reproducibility, linearity, sensitivity, and accuracy, were evaluated. The method was applied to determine bioactive flavone derivatives in seven Chinese herbs.
Co-reporter:Yuming Dong, Xiaofeng Chen, Yonglei Chen, Xingguo Chen, Zhide Hu
Journal of Pharmaceutical and Biomedical Analysis 2005 Volume 39(1–2) pp:285-289
Publication Date(Web):1 September 2005
DOI:10.1016/j.jpba.2005.02.032
An easy, rapid and simple nonaqueous capillary electrophoresis (NACE) method was developed for the identification and determination of four basic nitrogenous compounds, i.e. pseudoephedrine (PE), dextromethorphan (DXM), diphenhydramine (DHM) and chlorpheniramine (CLP). The most suitable running buffer was composed of 40 mM ammonium acetate, 10% acetonitrile (ACN) in methanol with a fused-silica capillary column (47 cm × 75 μm i.d.), 25 kV applied voltage and 25 °C capillary temperature. The calibration curves revealed linear relationships between the peak area for each analyte and its concentration (correlation coefficients: 0.9993 for PE, 0.9971 for DXM, 0.9991 for DHM, and 0.9995 for CLP, respectively). The relative standard deviations of the migration time and peak area of the four compounds were 0.37, 3.90, 0.73 and 0.68, and 2.80, 3.50, 1.60 and 3.70%, respectively. The method was successfully applied to determine the four compounds in five cold medicines, the recoveries of the four constituents ranging between 91 and 109%.
Co-reporter:Suling Feng, Jin Wang, Xingguo Chen, Jing Fan
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2005 Volume 61(Issue 5) pp:841-844
Publication Date(Web):March 2005
DOI:10.1016/j.saa.2004.06.008
A highly sensitive spectrofluorimetric method is proposed for the determination of trace amount of ascorbic acid using a new indication. The method is based on the inhibition of ascorbic acid on the oxidation of pyronine Y (PRY) by nitrite. The detection limit for ascorbic acid is 0.012 μg ml−1, the linear range of the determination is 0.02–0.36 μg ml−1. Analytical parameters, such as reagent concentration, pH, reaction temperature and time, were optimized. The relative standard deviations of eleven replication determinations of 0.12 and 0.24 μg ml−1 ascorbic acid were 1.4 and 0.72%, respectively. This method has been used to determine ascorbic acid in pharmaceuticals, vegetables, fruits and soft drink with satisfactory results.
Co-reporter:Yuqin Li, Shengda Qi, Xingguo Chen, Zhide Hu
Talanta 2005 Volume 65(Issue 1) pp:15-20
Publication Date(Web):15 January 2005
DOI:10.1016/j.talanta.2004.04.019
A nonaqueous capillary electrophoresis (NACE) method with direct on-column UV detection has been developed for the separation of the pharmaceutically important anthraquinones from the total grass of Xanthophytum attopvensis pierre extract. The separation of three main anthraquinones (1-hydroxy-2-methoxy-3-hydroxymethyl-9, 10-anthraquinone-1-O-β-d-glucoside (1), rubiadin- 1-methylether (2) and 1-methoxy-2-formyl-3-hydroxy-9, 10-anthraquinone (3)) was optimized with respect to concentration of sodium cholate (SC) and acetic acid, addition of acetonitrile (ACN), and applied voltage. Baseline separation was obtained for the three analytes within 5 min using a running buffer containing 50 mM sodium cholate (SC), 1.0% acetic acid and 40% ACN in methanol. The method of NACE for the separation and determination of bioactive ingredient in traditional Chinese medicines was discussed.
Co-reporter:Shengda Qi, Shuya Cui, Xingguo Chen, Zhide Hu
Journal of Chromatography A 2004 Volume 1059(1–2) pp:191-198
Publication Date(Web):3 December 2004
DOI:10.1016/j.chroma.2004.09.090
The present study reported the ionic liquid (IL) used as running electrolyte in capillary zone electrophoresis (CZE) with β-cyclodextrin (β-CD) as modifier for the separation of anthraquinones extract of Chinese herb Paedicalyx attopevensis Pierre ex Pitard. The optimum running electrolyte was 60 mM 1-butyl-3-methylimizolium tetrafluoroborate (1B-3MI-TFB) solution with 4.0 mM β-CD. The pH was 10.00 and the applied voltage was 20 kV with detection at 254 nm. The present method was compared with others and the effect of Joule heating was discussed as well. More significantly, this method is the development of the ionic liquids application to the capillary electrophoresis.
Co-reporter:Runping Jia, Yan Shen, Haiqing Luo, Xingguo Chen, Zhide Hu, Desheng Xue
Applied Surface Science 2004 Volume 233(1–4) pp:343-351
Publication Date(Web):30 June 2004
DOI:10.1016/j.apsusc.2004.03.246
Abstract
For the first time, an organic dye, morin, and bio-macromolecule, lysozyme (Lys) were embedded in the holes of anodic porous alumina (P-Al). The photoluminescent (PL) spectra of dye and dye–protein immersed in P-Al film were investigated and compared with those of liquid solutions. It was found that their PL positions are similar to that of dye–Al3+ in ethanol solution, and the PL intensity of embedded dye can be enhanced greatly by the introduction of lysozyme. We ascribe that the appearance of the PL band detected is attributed to the formation of morin–Al complex in the pores with its inner wall involved. A likely orderly model was proposed to explain the observed enhancing phenomena of PL due to the coexistence of morin and lysozyme in the P-Al layer, which has been proved by UV and FTIR measurements.
Co-reporter:Yan Shen, Run-Ping Jia, Hai-Qing Luo, Xing-Guo Chen, De-Sheng Xue, Zhi-De Hu
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2004 Volume 60(Issue 5) pp:1007-1011
Publication Date(Web):April 2004
DOI:10.1016/S1386-1425(03)00332-9
In this paper, the photoluminescence (PL) of porous anodized aluminum oxide (AAO) impregnated with essentially nonfluorescent morin and morin–bovine serum albumin (BSA) was investigated for the first time, respectively. The evident PL bands similar to that of morin–Al3+ complex in solution were observed and the intensity of the latter with morin–BSA was much greater than that of the former with only morin. Moreover, the enhancement increased with the larger pore diameter of the AAO membranes. The appearance of PL bands might be ascribed to the formation of morin–Al complexes in the AAO pores with its inner wall involved. A likely orderly luminescent model was proposed to be responsible for the observed enhancing phenomena of PL due to the coexistence of morin and BSA in the AAO pores.
Co-reporter:Hong Gao, Liandi Lei, Jiaqin Liu, Qin Kong, Xingguo Chen, Zhide Hu
Journal of Photochemistry and Photobiology A: Chemistry 2004 Volume 167(2–3) pp:213-221
Publication Date(Web):1 October 2004
DOI:10.1016/j.jphotochem.2004.05.017
In this work, the binding of 2-hydroxy-3-nitro-9-fluorenone (HNF; a new reagent with antitumour activity) to human serum albumin (HSA) was investigated by fluorescence spectroscopy combined with UV-Vis absorption, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectrophotometric techniques under simulative physiological conditions for the first time. A strong fluorescence quenching reaction of HNF to HSA was observed and the quenching mechanism was suggested as static quenching according to the Stern–Volmer (S–V) equation. The binding constants of HNF with HSA at 300, 310 and 320 K were calculated as 6.08×105, 3.80×105 and 2.79×105 M−1, respectively, and corresponding numbers of binding sites (n) were 1.1, 1.0 and 1.0. Experimental results observed showed that the binding of HNF to HSA induced conformational change of HSA. The quantitative analysis data of CD spectra from that of the α-helix 60.3% in free HSA to 56.5% in the HNF–HSA complex further confirmed that the secondary structure of the protein was modified by HNF. The thermodynamic parameters, standard enthalpy change (ΔH°) and the standard entropy change (ΔS°), were obtained to be −31.10 kJ mol−1 and 6.87 J mol−1 K−1, respectively, which indicated that a hydrophobic force played a major role in the interaction of HNF with HSA. All these experimental results and theoretical data clarified that HNF could bind to HSA and be effectively transported and eliminated in body, which could be a useful guideline for further drug design.
Co-reporter:Yuqiao Cheng, Hongli Chen, Yuqin Li, Xingguo Chen, Zhide Hu
Talanta 2004 Volume 63(Issue 2) pp:491-496
Publication Date(Web):28 May 2004
DOI:10.1016/j.talanta.2003.11.027
A novel, rapid and accurate method for the separation and determination of aloperine (ALP), sophoridine (SRI), matrine (MT) and oxymatrine (OMT) has been developed by combination of flow injection (FI) with microfluidic capillary electrophoresis (CE) for the first time. In the present paper, a continuous sample introduction interface was described. The interface with an H-channel structure was produced using a non-lithographic approach. The H-channel structure was fixed on a planar plastic base utilizing a horizontal 6.5 cm-long separation capillary with two vertical sidearm tubes on each end that served as inlet and outlet flow-through electrode reservoirs. The inlet reservoir also functioned as interface for coupling to the FI system. The buffer solution used was a 50 mmol l−1 borate solution with the pH adjusted to 8.80 with 2 mol l−1 HCl. The performance of the system was demonstrated in the separation and determination of ALP, SRI, MT and OMT with UV detection at 215 nm, achieving baseline separation within 2 min. A series of samples was injected repeatedly without current interruption and subsequent rinsing, and the contents of these four bio-alkaloids in two marketed drugs were determined with satisfactory recovery by this proposed method.
Co-reporter:Jia Runping, Zhai Honglin, Shen Yan, Chen Xingguo, Hu Zhide
Talanta 2004 Volume 64(Issue 2) pp:355-360
Publication Date(Web):8 October 2004
DOI:10.1016/j.talanta.2004.02.030
For the first time, the relationship between the structural parameters of dye molecule and the enhanced resonance light scattering (RLS) of dye–human serum albumen (HSA) was investigated using chemometrics technique. The data set of the enhanced RLS intensity of the dye–HSA was obtained under the same experimental conditions for 22 dyes. After calculated with HyperChem software and selected by stepwise regression approach, six structural parameters for the maximum RLS wavelength were used in multivariable linear regression (MLR) (R=0.932), seven structural parameters for the corresponding enhanced RLS intensity were employed by MLR (R=0.934). According to these models, the maximum RLS wavelength and the enhanced RLS intensity are both attributed to the spatial structure and energies of dye.
Co-reporter:Shufang Wang, Yanqi Wu, Yong Ju, Xingguo Chen, Wenjie Zheng, Zhide Hu
Journal of Chromatography A 2003 Volume 1017(1–2) pp:27-34
Publication Date(Web):31 October 2003
DOI:10.1016/j.chroma.2003.08.032
A simple and sensitive micellar electrokinetic capillary chromatography (MEKC) method was developed for the separation and determination of six flavonoids in Epimedium brevicornum Maxim. Field-enhanced sample injection with reverse migrating micelles (FESI-RMM) was used for on-line concentration of the flavonoids. An electrolyte containing 20 mM H3PO4, 100 mM SDS, 20% acetonitrile and 2% 2-propanol (pH 2.0) was chosen as the electrophoretic buffer. By optimizing the stacking conditions, about 40–360-fold improvement in the detection sensitivity was obtained for the flavonoids.
Co-reporter:Hong Li Chen;Xing Guo Chen;Liu Yin Fan;Zhi De Hu
Journal of Separation Science 2003 Volume 26(Issue 15‐16) pp:1376-1382
Publication Date(Web):18 SEP 2003
DOI:10.1002/jssc.200301549
A simple, rapid microfluidic capillary electrophoresis system with a continuous sample introduction interface is described in the present paper. The interface with an H-channel structure was produced using a non-lithographic approach. The H-channel structure fixed on a planar plastic base utilized a horizontal 6.5-centimeter-long separation capillary with two vertical sidearm tubes on each end that served as inlet and outlet flow-through electrode reservoirs. The inlet reservoir also functioned as interface for coupling to the FI system. The performance of the system was demonstrated in the separation and determination of trimethoprim (TMP), sulfadiazine (SDZ), and sulfamethoxazole (SMZ) with UV detection at 214 nm, achieving baseline separation within 2.5 min. The sample throughput rate can reach up to 30 samples h–1. The repeatability (defined as relative standard deviation, RSD) was 2.23%, 1.19%, 2.64% with peak height evaluation and 2.43%, 1.46%, 3.58% for peak area evaluation, respectively. The limits of detection (S/N = 3) were 0.17 μg/mL, 1.05 μg/mL, and 1.28 μg/mL for TMP, SDZ, and SMZ, respectively. This technique has been applied to the analysis of two commercial pharmaceutical preparations containing TMP, SDZ, and SMZ for the first time and has achieved satisfactory results.
Co-reporter:Hong Li Chen;Liu Yin Fan;Zhi De Hu;Zheng Feng Zhao;Martin Hooper;Xing Guo Chen
Journal of Separation Science 2003 Volume 26(Issue 9‐10) pp:863-868
Publication Date(Web):27 JUN 2003
DOI:10.1002/jssc.200301517
A novel, rapid, and simple capillary electrophoresis (CE) method has been developed for the determination of aspirin by on-line treatment with alkali. Such on-line reaction with 0.20 mol/L NaOH solution for 2.5 min at 45°C automatically and reproducibly converts aspirin into its hydrolysis product salicylic acid. Analysis is carried out in less than 12 min after conversion of aspirin in a flow injection (FI) system coupled to a CE instrument via a split-flow interface cell, and a sampling frequency of 9 h–1 is achievable. The on-line conversion method has been used to determine aspirin in four commercial pharmaceutical preparations, and the results are satisfactory.
Co-reporter:Wenjie Zheng, Shufang Wang, Xingguo Chen, Zhide Hu
Talanta 2003 Volume 60(Issue 5) pp:955-960
Publication Date(Web):27 July 2003
DOI:10.1016/S0039-9140(03)00178-4
A simple, rapid, selective and reproducible capillary electrophoresis (CE) method was firstly developed for the identification and determination of isofraxidin and fumaric acid in a traditional Chinese herb Sarcandra glabra and its medicinal preparations. The buffer solution used in this method was 7.5 mM NaH2PO4 and 7.5 mM borax solution adjusted to pH 8.60. The linear calibration range was 1.25–800 μg ml−1 (r=0.9997) for isofraxidin and 10–800 μg ml−1 (r=0.9992) for fumaric acid, respectively. Under the optimum conditions, the relative standard deviation (R.S.D.) values of the migration time and the peak area were 0.47, 3.45% for isofraxidin and 0.83, 3.24% for fumaric acid, respectively. The recoveries ranged between 95.4–103.8% for isofraxidin and 97.1–104.7% for fumaric acid, respectively. The contents of isofraxidin and fumaric acid in Sarcandra glabra and two kinds of Sarcandra glabra-containing Chinese medicinal preparations were successfully determined within 8 min.
Co-reporter:Xinan Wu, Xingguo Chen, Zhide Hu
Talanta 2003 Volume 59(Issue 1) pp:115-121
Publication Date(Web):2 January 2003
DOI:10.1016/S0039-9140(02)00470-8
A high-performance liquid chromatographic (HPLC) method is described for the simultaneous determination of honokiol and magnolol in rat plasma. The plasma was deproteinized with acetonitrile which contained an internal standard (diphenyl) and was separated from the aqueous layer by adding sodium chloride. Honokiol and magnolol are extracted into the acetonitrile layer with high yield, and determined by reversed-phase HPLC and ultraviolet detection. The limits of quantitation for honokiol and magnolol were 13 and 25 ng ml−1 in plasma, respectively, and recovery of both analytes was greater than 93%. The assay was linear from 20 to 200 ng ml−1 for honokiol and from 40 to 400 ng ml−1 for magnolol. Variation over the range of the standard curve was less than 15%. The method was used to determine the concentration–time profiles of honokiol and magnolol in the plasma following rectal administration of Houpo extract at a dose of 245 mg kg−1, equivalent to 13.5, 24.4 mg kg−1 of honokiol and magnolol, respectively.
Co-reporter:Xinan Wu, Fumiyoshi Yamashita, Mitsuru Hashida, Xingguo Chen, Zhide Hu
Talanta 2003 Volume 59(Issue 5) pp:965-971
Publication Date(Web):10 April 2003
DOI:10.1016/S0039-9140(03)00009-2
A simple high-performance liquid chromatography (HPLC) method is described for the determination of matrine in rat plasma. The plasma was deproteinized with acetonitrile that contained an internal standard (phenacetin) and was separated from the aqueous layer by adding sodium chloride. Matrine was extracted into the acetonitrile layer with high yield, and determined by reversed-phase HPLC (column: YMC-pack ODS-A, 5 μm, 150×4.6 mm, I.D.; eluent: acetonitrile–0.02 mol ammonium acetate buffer–triethylamine (35:65:0.035, v/v/v) and ultraviolet detection (220 nm). The limit of quantitation for matrine was 200 ng ml−1 in plasma, and the recovery was greater than 89%. The assay was linear from 0.5 to 50.0 μg ml−1. Variation over the range of the standard curve was less than 6%. The method was used to determine the concentration–time profiles of matrine in the plasma following oral administration of matrine aqueous solution or bolus injection from which the fractions of matrine reaching the systemic circulation were estimated by a deconvolution method for the first time.
Co-reporter:Run-Ping Jia, Li-Jun Dong, Qian-Feng Li, Xing-Guo Chen, Zhi-De Hu
Talanta 2002 Volume 57(Issue 4) pp:693-700
Publication Date(Web):10 June 2002
DOI:10.1016/S0039-9140(02)00075-9
A simple, sensitive and selective method has been developed for the determination of protein using resonance light scattering (RLS) technique. The method is based on the interaction of protein and arsenazo-DBC-Al3+ in the pH range of 5.0–7.0, which causes a substantial enhancement of the resonance scattering signal of arsenazo-DBC-Al3+ in the wavelength range of 300–550 nm with the maximum RLS platform at 405–420 nm. With this method, 2.50–50.00 μg ml−1 of bovine serum albumin (BSA) and 2.50–60.00 μg ml−1 of human serum albumin (HSA) can be determined, and the detection limits, calculated three times the standard deviation (S.D.) of six blank measurements, for BSA and HSA were 123.4 and 89.6 ng ml−1, respectively. Moreover, the method is free from interference from many amino acids and metal ions. The method, with high sensitivity, selectivity and reproducibility, was satisfactorily applied to the determination of total protein in human serum samples. Mechanism studies indicated that arsenazo-DBC-Al3+ could bind to BSA depending mainly on electrostatic forces, which results in enhanced RLS in the arsenazo-DBC-Al3+–protein system.
Co-reporter:Runping Jia, Lijun Dong, Qianfeng Li, Xingguo Chen, Zhide Hu, Yukio Nagaosa
Analytica Chimica Acta 2001 Volume 442(Issue 2) pp:249-256
Publication Date(Web):5 September 2001
DOI:10.1016/S0003-2670(01)01145-X
Based on the weak Rayleigh light scattering (RLS) of the complex of dibromomethyl (DBM)–Arsenazo–Al(III) which can be enhanced by the addition of protein in weak acidic solutions, a novel method for the determination of protein concentrations has been proposed by using a commonly used spectrofluorimeter. Four proteins, including bovine serum albumin (BSA), human serum albumin (HSA), lysozyme and egg albumin were tested. The dynamic range, for example HSA is 2.5–50.0 μg ml−1 and the 10σ determination limit is 83 ng ml−1. This method has been applied to the determination of proteins in human serum samples, and the results are very close to those provided by clinical physicians. There is very little interference from amino acids, metal ions and other coexisting compounds. The assay is convenient, rapid, inexpensive and simple.
Co-reporter:Sun Gang, Zhou Yongyao, Wang Huaiwen, Chen Hongli, Chen Xingguo and Hu Zhide
Analyst 2000 vol. 125(Issue 5) pp:921-925
Publication Date(Web):10 Apr 2000
DOI:10.1039/A908689G
A sensitive and selective spectrophotometric flow injection
method has been developed for the determination of uranium(VI)
in ore samples, based on the reaction of uranium(VI) with
p-acetylchlorophosphonazo (CPA-pA) in a HNO3 medium.
Most of the interfering ions were effectively eliminated by the masking
reagent, diethyleneaminepentaacetic acid (DTPA). Artificial neural networks
coupled with an orthogonal design and penalty algorithm were applied to the
modeling of the proposed flow injection system and optimization of the
experimental conditions. An orthogonal design was utilized to design the
experimental protocol, in which three variables were varied simultaneously.
ANNs with a faster back propagation (BP) algorithm were used to model the
system. Optimum experimental conditions were generated automatically by
using jointly ANNs and optimization algorithms in terms of sensitivity and
sampling rate. In the U(VI)–CPA-pA system, Beer’s
law was obeyed in the range 1.0–23.0 μg mL−1, the
detection limit for uranium(VI) was 0.3 μg
mL−1 and the sampling rate was 100 h−1.
The method was applied to the determination of uranium(VI) in
ore samples with satisfactory results. It was shown that this method had
advantages over traditional methods in respect of improvement in the
ability of optimization and reduction in analysis time.
Co-reporter:Lijun Dong, Xingguo Chen, Zhide Hu
Journal of Molecular Structure (26 November 2007) Volume 846(Issues 1–3) pp:
Publication Date(Web):26 November 2007
DOI:10.1016/j.molstruc.2007.01.034
The effect of Cal-Red on the structure of human serum albumin (HSA) was studied using Resonance light scattering (RLS), Fourier transformed Infrared (FT-IR) and Circular dichroism (CD) spectroscopic methods. The RLS spectroscopic results show that the RLS intensity of HSA was significantly increased in the presence of Cal-Red. The binding parameters of HSA with Cal-Red were studied at different temperatures of 289, 299, 309 and 319 K at pH 4.1. It is indicated by the Scatchard plots that the binding constant K decreased from 4.03 × 108 to 7.59 × 107 l/mol and the maximum binding number N decreased from 215 to 152 with increasing the temperature, respectively. The binding process was exothermic and spontaneous, as indicated by the thermodynamic analyses, and the major part of the binding energy is hydrophobic interaction. The enthalpy change ΔH0, the free energy change ΔG0 and the entropy change ΔS0 of 289 K were calculated to be −42.75 kJ/mol, −47.56 kJ/mol and 16.66 J/mol K, respectively. The alterations of protein secondary structure in the presence of Cal-Red in aqueous solution were quantitatively calculated from FT-IR and CD spectroscopy with reductions of α-helices content about 5%, β-turn from 10% to 2% and with increases of β-sheet from 38% to 51%.
Co-reporter:Ximin Zhou, Wenjuan Lü, Li Su, Yalei Dong, Qianfeng Li and Xingguo Chen
Organic & Biomolecular Chemistry 2012 - vol. 10(Issue 41) pp:NaN8321-8321
Publication Date(Web):2012/08/28
DOI:10.1039/C2OB25967B
The binding affinity between hydroxyproline (Hyp) and human serum albumin (HSA) was investigated under simulated physiological conditions, using molecular modeling in combination with steady-state fluorescence, synchronous fluorescence, time-resolved fluorescence, UV-vis absorption, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopy. Molecular modeling studies suggested that the Hyp molecule was situated within subdomain IIA of HSA. The fluorescence quenching analysis indicated that the fluorescence of HSA was quenched by Hyp with a dynamic quenching mechanism. The binding constants were calculated according to Scatchard's equation and implied that Hyp can bind to different binding sites on HSA. The thermodynamic analysis implied that hydrophobic forces were the main interaction in the Hyp–HSA system, which was found to be in line with the results of molecular modeling. Furthermore, the conformational structure of HSA was changed with various amounts of Hyp, which was confirmed by synchronous fluorescence, UV-vis absorption, CD, and FT-IR spectra.
Co-reporter:Hui-qing Song, Qian Zhu, Xue-jing Zheng and Xing-guo Chen
Journal of Materials Chemistry A 2015 - vol. 3(Issue 19) pp:NaN10377-10377
Publication Date(Web):2015/04/01
DOI:10.1039/C5TA00280J
In this paper, a simple one-pot hydrothermal procedure to create three-dimensional (3D) graphene/multiwalled carbon nanotubes/Pd (G/MWCNTs/Pd) composite hydrogels with a unique porous nanostructure was reported. During the formation of the G/MWCNTs/Pd composites, 2D graphene sheets and 1D MWCNTs were self-assembled to form interconnected porous microstructures and ultrafine Pd NPs were in situ grown on the 3D carbon-based skeleton simultaneously. In the as-obtained nanocomposites, MWCNTs not only prevented the close restacking of graphene sheets to increase the specific surface area but also provided an additional transport path to the catalyst surfaces which facilitated reactant transport. The G/MWCNTs/Pd composites proved to be an efficient, recyclable, and robust catalyst for the Suzuki cross-coupling reactions under mild aerobic conditions, which was attributed to the 3D macroporous framework with high specific surface area, numerous activation sites, and efficient transport pathways for improving the catalytic performance. Moreover, catalyst separation could be easily achieved by simple filtration, and the catalyst could be reused for at least six runs without significant loss in catalytic activity. Additionally, nearly no Pd species was released from the G/MWCNTs/Pd composites during the catalytic reactions, showing the heterogeneity in the present catalysis system.
Co-reporter:
Analytical Methods (2009-Present) 2013 - vol. 5(Issue 4) pp:
Publication Date(Web):
DOI:10.1039/C2AY26391B
In this study, a novel colorimetric method for rapid, sensitive and low-cost detection of glyphosate was developed using cysteamine-stabilized gold nanoparticles (CS-AuNPs). The CS-AuNPs could be aggregated easily in the presence of glyphosate through electrostatic interaction in acidic medium, resulting in a shift in the surface plasmon band and a consequent color change from red to blue (or purple). Therefore, the content of glyphosate could be determined by monitoring with the naked eyes or a UV-Vis spectrophotometer. The detection limit of the present method for glyphosate was 5.88 × 10−8 M, with the linear range of 0.500–7.00 μM. The proposed method is a promising approach for on-site screening of glyphosate content in environmental water samples without using any costly instruments.
Co-reporter:Hai-juan Zhang, Sheng-da Qi, Xiao-ying Niu, Jing Hu, Cui-ling Ren, Hong-li Chen and Xing-guo Chen
Catalysis Science & Technology (2011-Present) 2014 - vol. 4(Issue 9) pp:NaN3024-3024
Publication Date(Web):2014/04/16
DOI:10.1039/C4CY00072B
Separation and recycling of catalysts after catalytic reactions are critically required to reduce the cost of catalysts as well as to avoid the generation of waste in industrial applications. In this paper, ultrafine noble metallic nanoparticles are incorporated into cauliflower-like porous magnetic metal–organic frameworks (MOFs). With the restriction effects of the pore/surface structure in the MOFs, “surfactant-free” metallic nanoparticles are successfully obtained on a 2–3 nm scale. In addition, both the thickness of MOFs shell and the content of noble metallic NPs are tunable on the MOFs coating. Moreover, the microspheres exhibit excellent performance for the catalytic reduction of p-nitrophenol with a turnover frequency of 3094 h−1. The uniform cavities in the MOFs shell provide docking sites for p-nitrophenol and act as confinement nanoreactors, which greatly improves the catalytic performance. Most importantly, the magnetically responsive microspheres can be easily recovered by a magnetic field and show excellent reusability. The as-prepared catalyst also shows good activity for the reduction of other nitrobenzenes. Consequently, this work provides a highly active, magnetically isolable, and recyclable catalyst, which can be used for various catalytic industrial processes. The fundamental model can be further employed in a variety of biomedical fields including drug delivery and biological molecules separation.
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