Co-reporter:Jincan He;Gongke Li
Microchimica Acta 2017 Volume 184( Issue 7) pp:2365-2373
Publication Date(Web):27 April 2017
DOI:10.1007/s00604-017-2263-7
The authors describe a fluorescence amplification strategy for selective and sensitive fluorescent assays based on aptamer-triggered directional hydrolysis and on the use of metal organic frameworks (MOFs) of type MIL-101. The method is implemented by mixing MIL-101, fluorescein-labeled DNA probes, exonuclease of type RecJf, and targets. A smart design of the three-adenine bulge on the DNA probe facilitates exonuclease-assisted directional hydrolysis, making the strategy universal for determination of both proteins and small molecules as well. Good selectivity is accomplished due to the use of MIL-101 protected aptamers, while high sensitivity resulted from exonuclease-assisted target-recycling signal amplification. The power of the method is demonstrated by analyzing the two model analytes thrombin (a fairly large protein) and oxytetracycline (OTC; a small molecule antibiotic). The limits of detection are 15 pM for thrombin and 4.2 nM for OTC. This is two orders of magnitude lower than that of conventional 1:1 homogeneous fluorescence assays. The strategy was successfully applied to the analysis of thrombin and OTC in real samples. In our perception, the strategy presented here has a wide scope for selective and sensitive detection of trace analytes for which appropriate DNA probes can be identified.
Co-reporter:Langjun Zhou;Yi Peng;Gongke Li
Journal of Analysis and Testing 2017 Volume 1( Issue 1) pp:
Publication Date(Web):2017 January
DOI:10.1007/s41664-017-0006-8
Conjugated microporous polymers (CMPs) are a kind of porous skeleton polymers, which are characterized by extended conjugated skeletons, large specific surface area and structure stability. In this work, a facile and versatile method was developed to fabricate flexible conjugated microporous polymer films for fast detecting the total quantity of developing agents and their oxidation products. Conjugated microporous polymer films were synthesized through in situ one-step approach by Suzuki coupling reaction. With such merits such as intense luminescence, easy synthesis and disposability, the polymer films were employed to detect developers based on fluorescence quenching in the printing wastewater. A linear response to p-benzoquinone, oxidation product of developers, was obtained in the range of 0.05–0.5 μmol·L−1, with a detection limit of 0.015 μmol·L−1. The strategy for in situ growth of flexible polyphenylene-conjugated microporous polymer (PP-CMP) films seems to be a very portable and general method for meeting different analytic purposes.
Co-reporter:Langjun Zhou, Yuling Hu, and Gongke Li
Analytical Chemistry 2016 Volume 88(Issue 13) pp:6930
Publication Date(Web):June 10, 2016
DOI:10.1021/acs.analchem.6b01708
Conjugated microporous polymers (CMPs), linked by a covalent bond to form an extension of the aromatic ring skeleton, are microporous materials characterized by a highly conjugated structure and high stability. The present study reported on a novel strategy for the synthesis of CMPs with built-in magnetic nanoparticles for excellent enrichment of trace hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) in human urine. We modified Fe3O4 nanoparticles with boronic acid groups and then reacted the nanoparticles with reactive monomers of polyphenylene conjugated microporous polymer (PP-CMP) to anchor the magnetic components in the PP-CMP framework. Chemical bonding between Fe3O4 nanoparticles and PP-CMP networks, together with equally firm covalent linkage and rigidity of the PP-CMP network, endows the magnetic PP-CMP with remarkable chemical stability and durability, even in harsh conditions. Magnetic PP-CMP has the characteristics of high conjugation ability, highly porous structure, and magnetism, which makes it an ideal magnetic adsorbent for trace analytes with aromatic conjugation structure. The adsorption mechanism of OH-PAHs on magnetic PP-CMP was investigated and demonstrated that hydrophobic interaction was important for the contribution of interaction between adsorbents and target analytes, together with the assistance of π–π stacking interaction. For the application, the magnetic PP-CMP was used for the enrichment of trace OH-PAHs in human urine of both smokers and nonsmokers in combination with high-performance liquid chromatography with fluorescence detection (HPLC-FLD). It showed good selectivity and excellent sensitivity to these OH-PAHs. Their detection limits were low and in the range of 0.01–0.08 μg·L–1. The OH-PAHs were detected with different amounts from 0.054 to 0.802 μg·L–1 in urine samples from smokers and nonsmokers. The recoveries were found to be 76.0%–107.8%. The results indicate that the magnetic PP-CMP offers an efficient enrichment method for trace OH-PAHs in human urine.
Co-reporter:Kaige Zhang, Su Yao, Gongke Li and Yuling Hu
Nanoscale 2015 vol. 7(Issue 6) pp:2659-2666
Publication Date(Web):24 Dec 2014
DOI:10.1039/C4NR07082H
A simple, fast, reproducible and efficient one-step fabrication method was successfully developed to prepare gold nanoparticle/carbon nanosheet (Au NP/CNS) hybrids by using sonoelectrochemistry. This method involved simultaneous generation of carbon nanosheets (CNSs) by oxidation of a graphite anode and generation of Au NPs by reduction of AuCl4− on the surface of the cathode. Then the Au NPs modified with poly(diallyl dimethyl ammonium chloride) were self-assembled on the surface of the CNS. A homemade sonoelectrochemical device that provided both high-intensity electric and ultrasonic fields was applied. The ability to obtain Au NPs with a controlled size and distribution on the surface of the CNS benefitted from the synergistic effect of the electric field and ultrasonic field. The Au NPs on the CNS surface exhibited distinctive and high-quality SERS activity. The enhancement factor of the developed substrate was 1.2 × 106 using 4-aminothiophenol as the probe molecule. The Au NP/CNS hybrid showed a great increase of Raman signals for aromatic molecules because of the high affinity of the CNS for aromatic molecules and the SERS activity of Au NPs. This SERS substrate also showed charge selectivity for cationic aromatic dyes, due to the negative charge on the surface of the CNS. Subsequently, the potential practical application of the SERS substrate was evaluated by quantitative analysis of adenine. The results suggest that Au NP/CNS materials as sensitive SERS-active substrates have great potential for detection of biomolecules.
Co-reporter:Kaige Zhang, Gongke Li and Yuling Hu
Nanoscale 2015 vol. 7(Issue 40) pp:16952-16959
Publication Date(Web):14 Sep 2015
DOI:10.1039/C5NR05718C
The surface-enhanced Raman spectroscopy (SERS) technique is of great importance for insight into the transient reaction intermediates and mechanistic pathways involved in heterogeneously catalyzed chemical reactions under actual reaction conditions, especially in water. Herein, we demonstrate a facile method for in situ synthesis of nanocrystalline magnesium oxide–Ag(0) (nano MgO–Ag(0)) hybrid nanomaterials with dispersed Ag nanoparticles (Ag NPs) on the surface of nanocrystalline magnesium oxide (nano MgO) via Sn2+ linkage and reduction. As a benefit from the synergy effect of nano MgO and Ag NPs, the nano MgO–Ag(0) exhibited both excellent SERS and catalytic activities for the reduction of 4-nitrothiophenol in the presence of NaBH4. The nano MgO–Ag(0) was used for real-time monitoring of the catalytic reaction process of 4-nitrothiophenol to 4-aminothiophenol in an aqueous medium by observing the SERS signals of the reactant, intermediate and final products. The intrinsic reaction kinetics and reaction mechanism of this reaction were also investigated. This SERS-based synergy technique provides a novel approach for quantitative in situ monitoring of catalytic chemical reaction processes.
Co-reporter:Jialiang Pan, Shu Jia, Gongke Li, and Yuling Hu
Analytical Chemistry 2015 Volume 87(Issue 6) pp:3373
Publication Date(Web):February 23, 2015
DOI:10.1021/ac504594d
Microporous organic polymers (MOPs) are an emerging class of functional porous materials for diverse potential applications. Typically, tailored microporous structures of MOPs are generated by linkages of organic polymerizable monomer building blocks, providing high permanent porosity and excellent stability. Herein, we reported the first example of the application of organic building block based MOPs (OBB-MOPs) as efficient enrichment media for sample preparation. A novel multilayer interbridging strategy was proposed to fabricate OBB-MOP coatings, and hereby SNW-1 (a kind of OBB-MOPs) was coated on silica substrate with well-controlled thickness. Strong covalent bonds throughout the network and interlayer bridging improved the durability of the coating significantly. Outstanding chemical stability was observed in diverse solvents as well as solutions with a wide range of pH or high ionic strength and even under extremely harsh conditions like boiling water. The SNW-1 coating possessed a microporous network structure constructed of conjugated and nitrogen-rich building blocks. Thus, the coating exhibited a superior enrichment performance of polycyclic aromatic hydrocarbons and volatile fatty acids (VFAs) over commercial coatings based on interactions including π–π affinity and acid–base interaction. For further application, this coating was combined with gas chromatography/mass spectrometry for the noninvasive analysis of VFAs from tea leaf and tobacco shred samples. The low detection limits of 0.014–0.026 μg/L were achieved with the relative standard deviations (RSDs) between 4.3 and 9.0%. Consequently, trace original VFAs from the samples were detected. Good recoveries were obtained in the range of 90–129% and 77–118% with the corresponding RSDs (n = 3) of 2.6–9.3% and 1.9–10%, respectively.
Co-reporter:Jincan He, Gongke Li, and Yuling Hu
Analytical Chemistry 2015 Volume 87(Issue 21) pp:11039
Publication Date(Web):October 5, 2015
DOI:10.1021/acs.analchem.5b03049
Poor selectivity and biocompability remain problems in applying surface-enhanced Raman spectroscopy (SERS) for direct detection of proteins due to similar spectra of most proteins and overlapping Raman bands in complex mixtures. To solve these problems, an aptamer recognition induced target-bridged strategy based on magnetic chitosan (MCS) and silver/chitosan nanoparticles (Ag@CS NPs) using SERS was developed for detection of protein benefiting from specific affinity of aptamers and biocompatibility of chitosan (CS). In this process, one aptamer (or antibody) modified MCS worked as capture probes through the affinity binding site of protein. The other aptamer modified Raman report molecules encapsulated Ag@CS NPs were used as SERS sensing probes based on the other binding site of protein. The sandwich complexes of aptamer (antibody)/protein/aptamer were separated easily with a magnet from biological samples, and the concentration of protein was indirectly reflected by the intensity variation of SERS signal of Raman report molecules. To explore the universality of the strategy, three different kinds of proteins including thrombin, platelet derived growth factor BB (PDGF BB) and immunoglobulin E (lgE) were investigated. The major advantages of this aptamer recognition induced target-bridged strategy are convenient operation with a magnet, stable signal expressing resulting from preventing loss of report molecules with the help of CS shell, and the avoidance of slow diffusion-limited kinetics problems occurring on a solid substrate. To demonstrate the feasibility of the proposed strategy, the method was applied to detection of PDGF BB in clinical samples. The limit of detection (LOD) of PDGF BB was estimated to be 3.2 pg/mL. The results obtained from human serum of healthy persons and cancer patients using the proposed strategy showed good agreement with that of the ELISA method but with wider linear range, more convenient operation, and lower cost. The proposed strategy holds great potential in highly sensitive and selective analysis of target proteins in complex biological samples.
Co-reporter:Jia Liao, Dongmei Wang, Anqi Liu, Yuling Hu and Gongke Li
Analyst 2015 vol. 140(Issue 24) pp:8165-8171
Publication Date(Web):03 Nov 2015
DOI:10.1039/C5AN01657F
A novel porous Au@MIL-100 (Fe) core–shell structure in which a Au nanoparticle (AuNP) core is coated with a controllable uniform metal–organic framework shell has been fabricated by using a facile step-by-step procedure. The as-synthesized Au@MIL-100 (Fe) takes advantage of the high adsorption capability of the MIL-100 (Fe) shell and the localized surface plasmon resonance properties of the AuNP core, and was used as a hybrid surface enhanced Raman scattering (SERS) substrate. We discussed the fabrication, physical characterization, and SERS activity of our novel substrate, and found that this new substrate had controllable shell thickness, high stability and good SERS activity. The potential practical application of the novel SERS substrate was firstly evaluated by quantitative analysis of malachite green in aquaculture water. The method showed good linearity between 3.0 × 10−8–1.0 × 10−6 mol L−1 for malachite green with a correlation coefficient of 0.9945. The limit of detection (LOD) was 8.0 × 10−9 mol L−1. Then the applicability of Au@MIL-100 (Fe) as the SERS substrate for in situ detection of malachite green on the fish body indicated its great potential as a rapid and on-site detection analytical strategy. In addition, the preliminary investigation also shows that the Au@MIL-100 (Fe) has SERS activity toward carbon disulfide which would be a new strategy for SERS-based gas sensors.
Co-reporter:Yuling Hu, Dongmei Wang and Gongke Li
Analytical Methods 2015 vol. 7(Issue 15) pp:6103-6108
Publication Date(Web):15 Jun 2015
DOI:10.1039/C5AY01272D
Inspired by the bioadhesive and redox properties of the 3,4-dihydroxy-phenylalanine (DOPA) contained in marine mussels, a facile, rapid and economic colorimetric strategy for Hg2+ detection was developed. The abundant catechol chains on the surface of Ag@DOPA can reduce Hg2+ to Hg0 and form a Ag@DOPA@Hg nanostructure with the deposition of Hg0. The nanostructures of Ag@DOPA and Ag@DOPA@Hg were confirmed by X-ray photoelectron spectroscopy, transmission electron microscopy, elemental mapping and Fourier transform infrared spectroscopy. The formation of the Ag@DOPA@Hg nanostructure causes a change in the color of the Ag@DOPA colloids from golden yellow to purple blue, making it directly possible to detect Hg2+ using a colorimetric strategy within 5 minutes. With increasing concentrations of Hg2+ from 10 nM to 4 μM, the surface plasmon resonance absorbance peak of the Ag@DOPA colloids decreased in intensity and exhibited a good linear relationship with the Hg2+ concentration. The limit of detection was determined as 5 nM. Furthermore, this response was found to be highly selective for Hg2+ as the absorption spectrum was not affected by other metal ions such as Pb2+, Cr3+, Cu2+, Al3+, Ni2+, Co2+, etc. The excellent stability, selectivity and sensitivity of this strategy offer analytical practicability for Hg2+ detection in real water samples with recoveries in the range of 104–105% and cosmetic samples with recoveries in the range of 85–103%.
Co-reporter:Yuling Hu, Jia Liao, Dongmei Wang, and Gongke Li
Analytical Chemistry 2014 Volume 86(Issue 8) pp:3955
Publication Date(Web):March 19, 2014
DOI:10.1021/ac5002355
Surface-enhanced Raman scattering (SERS) signals strongly rely on the interactions and distance between analyte molecules and metallic nanostructures. In this work, the use of a gold nanoparticle (AuNP)-embedded metal–organic framework was introduced for the highly sensitive SERS detection. The AuNPs were in situ grown and encapsulated within the host matrix of MIL-101 by a solution impregnation strategy. The as-synthesized AuNPs/MIL-101 nanocomposites combined the localized surface plasmon resonance properties of the gold nanoparticles and the high adsorption capability of metal–organic framework, making them highly sensitive SERS substrates by effectively preconcentrating analytes in close proximity to the electromagnetic fields at the SERS-active metal surface. We discussed the fabrication, physical characterization, and SERS activity of our novel substrates by measuring the Raman signals of a variety of model analytes. The SERS substrate was found to be highly sensitive, robust, and amiable to several different target analytes. A SERS detection limit of 41.75 and 0.54 fmol for Rhodamine 6G and benzadine, respectively, was demonstrated. The substrate also showed high stability and reproducibility, as well as molecular sieving effect thanks to the protective shell of the metal–organic framework. Subsequently, the potential practical application of the novel SERS substrate was evaluated by quantitative analysis of organic pollutant p-phenylenediamine in environmental water and tumor marker alpha-fetoprotein in human serum. The method showed good linearity between 1.0 and 100.0 ng/mL for p-phenylenediamine and 1.0–130.0 ng/mL for alpha-fetoprotein with the correlation coefficients of 0.9950 and −0.9938, respectively. The recoveries ranged from 80.5% to 114.7% for p-phenylenediamine in environmental water and 79.3% to 107.3% for alpha-fetoprotein in human serum. These results foresee promising application of the novel metal–organic framework based composites as sensitive SERS-active substrates in both environmental and clinical samples.
Co-reporter:Haixian Lian;Gongke Li
Journal of Separation Science 2014 Volume 37( Issue 1-2) pp:106-113
Publication Date(Web):
DOI:10.1002/jssc.201301049
A novel metal-ion-mediated complex-imprinted-polymer-coated solid-phase microextraction (SPME) fiber used to specifically recognize thiabendazole (TBZ) in citrus and soil samples was developed. The complex-imprinted polymer was introduced as a novel SPME coating using a “complex template” constructed with Cu(II) ions and TBZ. The recognition and enrichment properties of the coating in water were significantly improved based on the metal ion coordination interaction rather than relying on hydrogen bonding interactions that are commonly applied for the molecularly imprinting technique. Several parameters controlling the extraction performance of the complex-imprinted-polymer-coated fiber were investigated including extraction solvent, pH value, extraction time, metal ion species, etc. Furthermore, SPME coupled with HPLC was developed for detection of TBZ, and the methods resulted in good linearity in the range of 10.0–150.0 ng/mL with a detection limit of 2.4 ng/mL. The proposed method was applied to the analysis of TBZ in spiked soil, orange, and lemon with recoveries of 80.0–86.9% and RSDs of 2.0–8.1%. This research provides an example to prepare a desirable water-compatible and specifically selective SPME coating to extract target molecules from aqueous samples by introducing metal ions as the mediator.
Co-reporter:Yuling Hu;Zelin Huang;Langjun Zhou;Dongmei Wang ;Gongke Li
Journal of Separation Science 2014 Volume 37( Issue 12) pp:1482-1488
Publication Date(Web):
DOI:10.1002/jssc.201400100
Nanoscale anatase titania was embedded within the porous chromium terephthalate MIL-101 under low-temperature hydrothermal treatment. The metal–organic framework shell acting as host matrix can effectively prevent the titania nanoparticles from aggregating and enable a good dispersion of these nanoparticles. The X-ray diffraction spectra, transmission electron micrography and X-ray photoelectron spectra clearly showed successful impregnation of the nano-sized anatase titania within the body of MIL-101. The resulting TiO2/MIL-101 nanocomposite was considered as bifunctional material with abundant adsorptive domains and catalytic domains, and was packed in a quartz tube as a convenient trapping and photocatalytic reactor for hazardous volatile pollutants. The composite showed great potential for adsorptive and photocatalytic degradation of these volatile pollutants, such as formaldehyde and o-xylene, which were online monitored by thermal desorption gas chromatography with mass spectrometric detection.
Co-reporter:Kaige Zhang;Lizhen Liang;Meiying Huang;Gongke Li
Microchimica Acta 2014 Volume 181( Issue 11-12) pp:1301-1308
Publication Date(Web):2014 August
DOI:10.1007/s00604-014-1248-z
We have developed a simple, rapid, and sensitive method for the determination of iodate in iodized salt and water samples. The method is making use of shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) and is based on the oxidation of hydroxylammonium chloride by iodate to produce nitrite which then is used to diazotize with p-nitroaniline. The resulting diazonium ion is then coupled to N-(1-naphthyl) ethylenediamine dihydrochloride to form an azo dye whose concentration is determined by SHINERS. The active substrate used in SHINERS is composed of gold nanoparticles coated with an ultrathin silica shell possessing pinholes on their surface. Various factors that influence the chemical reaction and the intensity of SHINERS were investigated. Under the optimal conditions, the Raman intensity is linearly related to the concentration of iodate in the 7.5–130.0 μg L−1 range, with a correlation coefficient of 0.9920. The limit of detection is 2.0 μg L−1, and the relative standard deviation is 7.5 % (for n = 5) at 1,138 cm−1 without additional sample pre-concentration. The method was successfully applied to the determination of iodate in iodized salt and water samples. The accuracy was assessed through recovery tests and independent analysis by a conventional titrimetric method.
Co-reporter:Yuling Hu, Zelin Huang, Jia Liao, and Gongke Li
Analytical Chemistry 2013 Volume 85(Issue 14) pp:6885
Publication Date(Web):June 13, 2013
DOI:10.1021/ac4011364
A facile and efficient strategy about the synthesis of a novel kind of hybrid magnetic metal–organic framework (MOF)-5 via chemical bonding assembly was reported. The covalent bonding established between the amino functionalized Fe3O4 nanoparticles and the surface of the metal organic framework improved the chemical stability and structure uniformity of the hybrid microcrystals. Combination of MOF-5 with Fe3O4 nanoparticles allows for facile withdrawal of the porous materials by magnetic decantation. The powder X-ray diffraction patterns of the hybrid magnetic MOF-5 showed the structure of the metal organic framework was not disturbed with the decoration of magnetic nanoparticles. The as-synthesized materials combine the favorable attributes of both magnetic characteristics of Fe3O4 nanoparticles and high porosity of metal organic framework, making them excellent candidates as adsorbents for magnetic enrichment of trace analytes. Their potential applications were explored by preconcentrating polycyclic aromatic hydrocarbons and gibberellic acids from environmental, food, and plant samples prior to gas chromatography–mass spectrometry (GC/MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), respectively. The results showed that the magnetic MOF-5 exhibited superior enrichment capacity for both of these nonpolar and polar analytes. The method demonstrated good precision (relative standard deviations (RSDs) of 1.7–9.7%), low detection limits (0.91–1.96 ng·L–1 for polycyclic aromatic hydrocarbons and 0.006–0.08 μg L–1 for gibberellic acid), and good linearity (correlation coefficients higher than 0.9949). The RSDs of batch-to-batch extraction were 2.9–11.2%. The magnetic MOF-5 was robust enough for repeatable use without damage of extraction performance.
Co-reporter:Jialiang Pan, Yichun Huang, Li Liu, Yuling Hu, Gongke Li
Journal of Chromatography A 2013 Volume 1316() pp:29-36
Publication Date(Web):5 November 2013
DOI:10.1016/j.chroma.2013.09.082
•A novel peak compression strategy (FSS) was proposed for online hyphenation of SPBE to UPLC.•SPE was online coupled with FSS-UPLC for the analysis of triazins.•An online in-tube SPME-derivatization-FSS-UPLC method for 24-epibrassinolide analysis.We have developed a novel ultrasensitive online analytical system which integrated solid-phase-based extraction (SPBE) techniques with ultra-high performance liquid chromatography (UPLC) based on a fractionized sampling and stacking (FSS) strategy. FSS was proposed as a novel peak compression strategy to prevent band broadening and distortion caused by excessive solvents with high elution strength, which has been a main obstacle to conjunction of sample preparation techniques with UPLC. Such a strategy was based on online dividing a sample solution into fractions by plugs of weak mobile phase, followed by head-column stacking process, aiming to obtain a quite sharp sample zone. FSS enables UPLC to tolerate much larger injection volume of solvents with high elution strength, which facilitates hyphenation of SPBE with UPLC without peak distortion or loss of sensitivity. On the basis above, an online SPBE-UPLC system was realized by FSS, and its applicability was preliminarily verified by the successful development of a sensitive solid phase extraction-FSS-UPLC method for the determination of triazines. Subsequently an integrated online system incorporating molecularly imprinted in-tube solid phase microextraction, derivatization and FSS-UPLC was developed for the analysis of ultra trace 24-epibrassinolide. The developed method was ultrasensitive with detection limit as low as 0.7 ng/L, and the linear range of the method was 3–5000 ng/L. The endogenous 24-epibrassinolide in pollen, flower and seed samples was determined, which showed satisfactory recoveries in the range of 81.2–116% and good precision with relative standard deviation (RSD) values between 4.7 and 9.7%. This online analytical method was sensitive, reliable, rapid and applicable to trace analysis in complex samples.
Co-reporter:Yuling Hu, Chaoyong Song, Jia Liao, Zelin Huang, Gongke Li
Journal of Chromatography A 2013 Volume 1294() pp:17-24
Publication Date(Web):14 June 2013
DOI:10.1016/j.chroma.2013.04.034
•Metal-organic framework MIL-101 was firstly fabricated in a PEEK tube.•This material demonstrated high adsorption of naproxen and its metabolite.•A special online extraction system coupled with HPLC was designed.•The developed approach offers a good sensitivity and repeatability.The metal-organic framework MIL-101 was fabricated in a polyetheretherketone (PEEK) tube as micro-trapping device, and applied to sorptive extraction of naproxen and its metabolite in urine samples. The remarkable water stability of the MIL-101 characterizes the material as being different from other moisture sensitive metal-organic framework. It is therefore suitable for extraction of pharmaceuticals from biological fluids. The adsorption isotherms in aqueous solution showed that the adsorption of naproxen on MIL-101 is endothermic. Additionally, MIL-101 exhibited higher extraction capacity to naproxen than that of C18-bonded silica and multi-walled nanotube. A specially designed in-tube sorptive extraction (ITSE) device endows the extraction process with the characteristic of rapidness, convenience, and easy of conjunction with high performance liquid chromatography (HPLC). Finally the MIL-101 based ITSE method coupled with HPLC and fluorescence detection was applied to analysis of naproxen and 6-O-desmethylnaproxen in urine samples. Parameters that influence the online extraction procedure, including pH of the sample solution, flow rate of extraction, sample volume, desorption solvents and time were investigated. The method is proved to be highly sensitive with the linear range of 0.05–6.0 μg L−1 and the limits of detection of 0.034 and 0.011 μg L−1 for naproxen and 6-O-desmethylnaproxen, respectively. The recoveries in urine samples were 85.3–98.3% for naproxen and 94.0–97.3% for 6-O-desmethylnaproxen with intra- and inter-day RSDs of 2.7–5.2% and 7.1–8.1%, respectively. Urine samples could be directly subjected to analysis without any additional sample pretreatment. The proposed method was demonstrated an efficient, flexible and versatile extraction tool which is ideally suitable for online conjunction with chromatographic methods.
Co-reporter:Jianxiang Huang, Yuling Hu and Gongke Li
Analytical Methods 2013 vol. 5(Issue 18) pp:4680-4686
Publication Date(Web):26 Jun 2013
DOI:10.1039/C3AY40745D
A selective, water-compatible and disposable complex imprinted polymer (CIP) membrane was prepared for L-phenylalanine detection combined with solid phase fluorescence detection. L-Phenylalanine coordinated with aluminum(III) acted as a complex template. The solid phase fluorescent signal was monitored to quantify L-phenylalanine after in situ derivatization with o-phthalaldehyde. Several parameters determining the performance of the CIP membrane were studied and optimized. The resulting CIP membrane exhibited good fluorescent response and selectivity towards L-phenylalanine in aqueous environments. The linear response of the CIP membrane to L-phenylalanine was in the range of 5.0–100 μmol L−1 with a limit of detection of 0.90 μmol L−1. The prepared CIP membrane was successfully applied in the analysis of L-phenylalanine in drinks and human urine with recoveries of 83.5–101.3% and RSDs ranging from 7.2% to 9.5%. The proposed method was compared with a high performance liquid chromatography method. The results showed that the developed method has satisfactory sensitivity, accuracy and precision for the selective determination of L-phenylalanine in water-abundant systems.
Co-reporter:Jianxiang Huang, Yufei Hu, Yuling Hu, Gongke Li
Talanta 2013 Volume 107() pp:49-54
Publication Date(Web):30 March 2013
DOI:10.1016/j.talanta.2012.12.054
In this work, a simple, low cost, selective and sensitive complex imprinted membrane (CIM) for solid-phase fluorescent detection was developed with terbium (III) salicylate as complex template. Terbium-sensitized luminescence was employed for monitoring salicylic acid (SA) based on the fluorescence enhancement effect of benzoic acid derivatives on lanthanide ion Tb (III). The resulting CIM showed good fluorescent response and high selectivity towards SA with Tb as pivot in protic solvents, while demonstrating better analytical performance than the controlled membranes. The optimized adsorption time was 10 min, indicating rapid kinetics of the imprinted membrane. The linear response of CIM to SA was from 0.20 to 10 mg/L with limit of detection (LOD) of 0.040 mg/L. The prepared CIM was successfully applied to the analysis of salicylic acid in pharmaceuticals and spiked human urine with recoveries of 80.6%–88.1%. The analytical results of the proposed method were in good agreement with those obtained by high performance liquid chromatography (HPLC) method, indicating that the developed membrane has acceptable practicability for fast determination of SA in real samples.Highlights► A simple, fast and disposable metal complex imprinted membrane was fabricated. ► The CIM was used for detection of salicylic acid on solid phase surface fluorescence. ► Novel method was suitable for rapid analysis of salicylic acid in real samples.
Co-reporter:Haixian Lian, Yuling Hu, Gongke Li
Talanta 2013 Volume 116() pp:460-467
Publication Date(Web):15 November 2013
DOI:10.1016/j.talanta.2013.07.022
•A novel metal ion-mediated complex imprinted membrane (CIM) was originally prepared.•CIM could selectively recognize naproxen in water medium according to its metal ion coordination.•A solid phase fluorescence method using CIM as the recognition material was proposed for direct determination of naproxen in complex samples.A novel metal ion-mediated complex imprinted membrane (CIM) was prepared by immobilization of complex imprinted polymer (CIP) onto a polypropylene membrane. CIP was introduced as a novel imprinted material using a “complex template” constructed with Cu (II) ion and naproxen that could improve the selective recognition and enrichment properties of the membrane in water medium based on the coordination interaction rather than hydrogen bonding interactions, which could make CIP a promising material to mimic biological recognition process. A simple, sensitive and selective solid surface fluorescence method was proposed for the determination of naproxen in pharmaceuticals sample, using the CIM as the recognition material. Under the optimum conditions, the CIM exhibited large adsorption capacity and high selectivity to naproxen. A good linearity was obtained in the range of 0.50–20 mg/L with an estimated detection limit of 0.11 mg/L. Finally, the proposed method was applied to the analysis of naproxen in pharmaceuticals without complicated pretreatment. The recoveries were 85.0% and 89.1% and the RSDs were 9.2% and 12.0%. The results were consistent with that obtained by high performance liquid chromatography. CIM integrated extraction, concentration, and detection into one-step, which could make the analytical procedure more efficient.
Co-reporter:Yuling Hu, Yifeng Fan, Zelin Huang, Chaoyong Song and Gongke Li
Chemical Communications 2012 vol. 48(Issue 33) pp:3966-3968
Publication Date(Web):27 Feb 2012
DOI:10.1039/C2CC17048E
In this work we demonstrated a facile method for in situ fabrication of the Fe3+–1,3,5-benzenetricarboxylic acid (BTC) metal–organic coordination polymer gel in a capillary, which was efficiently applied to the online enrichment of trace polycyclic aromatic hydrocarbons (PAHs) in environmental water and amphetamines drugs in urine.
Co-reporter:Jialiang Pan, Yuling Hu, Tingan Liang, Gongke Li
Journal of Chromatography A 2012 Volume 1262() pp:49-55
Publication Date(Web):2 November 2012
DOI:10.1016/j.chroma.2012.09.008
Co-reporter:Yuling Hu, Yifeng Fan, Gongke Li
Journal of Chromatography A 2012 Volume 1228() pp:205-212
Publication Date(Web):9 March 2012
DOI:10.1016/j.chroma.2011.08.057
A porous monolithic capillary column based on poly (methacrylic acid-co-ethylene glycol dimethacrylate) (poly (MAA-co-EGDMA)) was prepared using methanol and polyethylene glycol 6000 as mixed porogens. The monolith has the characteristics of good permeability, high extraction efficiency and long lifetime. Improved permeability of the monolith could realize sample loading with high flow rate. A simple and convenient construction that employed valve-switch technique was designed for online coupling of the monolithic capillary column to high performance liquid chromatography. In order to obtain optimum extraction efficiency, the extraction conditions including sample pH, sample volume, extraction and desorption flow rate were investigated. Under the optimum conditions, the enrichment factors were 180–362 for five estrogens, indicating remarkable preconcentration ability of the monolithic capillary column. The dynamic binding capacity (DBC) was estimated to be 3.73 mg mL−1 via frontal analysis. Finally the monolithic capillary column was successfully applied to online enrichment of estrogens from urine and milk samples followed by high performance chromatography. Low detection limits (S/N = 3) of the proposed method were achieved in the range of 0.04–0.35 μg L−1. The recoveries were 95.6–106.1% and 76.5–116.8% for the spiked urine and milk samples respectively, with the RSDs of 1.7–9.9%.
Co-reporter:Yuling Hu, Chaoyong Song, Gongke Li
Journal of Chromatography A 2012 Volume 1263() pp:21-27
Publication Date(Web):9 November 2012
DOI:10.1016/j.chroma.2012.09.029
An on line fiber-in-tube solid-phase microextraction (SPME) method was developed by longitudinally packing molecularly imprinted fibers (MIP-fibers) into PEEK tube as the online extraction unit. The obtained device therefore offers a reduced back pressure and rapid kinetics for its longitudinal channels, as well as possesses improved extraction capacity compared with traditional SPME method thanks to the increase of coating volume. In addition, the extraction of analytes was specific by using molecularly imprinted coatings, which greatly reduced the interference of sample matrix. To evaluate the new strategy, the PEEK tube was firstly packed with multiple ofloxacin imprinted fibers (OFL-MIP-fibers) for the analysis of four fluoroquinolones in animal-producing food samples. The extraction yields were significantly increased with the enrichment factors from 69 to 136. Sensitive results were achieved with the limits of detection as low as 0.016–0.11 μg/L (S/N = 3). This method was applied successfully to analysis of fluoroquinolones in pork liver and chicken samples with good repeatability (RSDs less than 7.2%). To expand the method, the PEEK tube was then filling with two different fibers imprinted by ofloxacin and sulfamethazine respectively in order to obtain simultaneous extraction of these two categories of antibiotic drugs. Preliminary results showed the hybrid packing strategy could simultaneously enrich the target analytes from complicated samples. The possibility of applying the method to pork liver sample spiked with fluoroquinolones and sulfonamides was also studied.Highlights► A novel multiple MIP fibers packed in-tube SPME method was developed. ► The new strategy is suitable for online analysis of trace antibiotic drug. ► The method is suitable to simultaneous analysis of different kind of compounds.
Co-reporter:Yuling Hu, Yuanwen Li, Ruijin Liu, Wei Tan, Gongke Li
Talanta 2011 Volume 84(Issue 2) pp:462-470
Publication Date(Web):15 April 2011
DOI:10.1016/j.talanta.2011.01.045
Novel magnetic molecularly imprinted polymer (MIP) beads using ractopamine as template for use in extraction was developed by microwave heating initiated suspension polymerization. Microwave heating, as an alternative heating source, significantly accelerate the polymerization process. By incorporating magnetic iron oxide, superparamagnetic composite MIP beads with average diameter of 80 μm were obtained. The imprinted beads were then characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and vibrating sample magnetometer. Highly cross-linked porous surface and good magnetic property were observed. The adsorption isotherm modeling was performed by fitting the data to Freundlich isotherm model. The binding sites measured were 3.24 μmol g−1 and 1.17 μmol g−1 for the magnetic MIP beads and the corresponding non-imprinted magnetic beads, respectively. Cross-selectivity experiments showed the recognition ability of the magnetic MIP beads to analytes is relative to degree of molecular analogy to the template. Finally, this magnetic MIP bead was successfully used for enrichment of ractopamine, isoxsuprine and fenoterol from ultrasonically extracted solution of pork and pig liver followed by high performance chromatography with fluorescence detection. The proposed method presented good linearity and the detection limits was 0.52–1.04 ng mL−1.The recoveries were from 82.0% to 90.0% and from 80.4% to 86.8% for the spiked pork and pig liver, respectively, with the RSDs of 5.8–10.0%. Combination of the specific adsorption property of the MIP material and the magnetic separation provided a powerful analytical tool of simplicity, flexibility, and selectivity.
Co-reporter:Yuling Hu;Ruijin Liu;Yuanwen Li ;Gongke Li
Journal of Separation Science 2010 Volume 33( Issue 13) pp:2017-2025
Publication Date(Web):
DOI:10.1002/jssc.201000063
Abstract
Ractopamine, as an alternative β-agonist to clenbuterol, is more and more used as leanness-enhancing agent in the swine industry. This work presents a new molecularly imprinted polymer (MIP) using ractopamine as template for dispersive solid-phase extraction of trace ractopamine and the structural related β-agonists in animal tissues. The binding properties and selectivity of MIP were investigated. High selectivity in polar environment was found, since the extraction capacity of ractopamine with the MIP was 4.5-fold as much as that with the non-imprinted polymer in acetonitrile. Cross-selectivity investigation indicates that the MIP preferentially binds the template and then the structural analogues according to their molecular similarity. Thermodynamic and kinetic investigation was performed to interpret the specific adsorption and molecular recognition of the MIP for ractopamine. Standard free energy, standard enthalpy, and standard entropy were determined. Related information suggested that adsorption of ractopamine onto MIP was an exothermic, spontaneous process. The MIP can be applied as dispersive solid-phase extraction material for enrichment of ractopamine, isoxsuprine, fenoterol and clenbuterol in complex samples before HPLC analysis. The method revealed detection limits of 0.20–0.90 μg/L, recoveries of 83.8–115.2 and 85.2–110.2% for the spiked pig muscle and pig liver, respectively, with the RSD from 2.5 to 8.8%.
Co-reporter:Yuling Hu, Yangyang Wang, Yufei Hu, Gongke Li
Journal of Chromatography A 2009 Volume 1216(Issue 47) pp:8304-8311
Publication Date(Web):20 November 2009
DOI:10.1016/j.chroma.2009.09.063
A novel liquid–liquid–solid microextraction (LLSME) technique based on porous membrane-protected molecularly imprinted polymer (MIP)-coated silica fiber has been developed. In this technique, a MIP-coated silica fiber was protected with a length of porous polypropylene hollow fiber membrane which was filled with water-immiscible organic phase. Subsequently the whole device was immersed into aqueous sample for extraction. The LLSME technique was a three-phase microextraction approach. The target analytes were firstly extracted from the aqueous sample through a few microliters of organic phase residing in the pores and lumen of the membrane, and were then finally extracted onto the MIP fiber. A terbutylazine MIP-coated silica fiber was adopted as an example to demonstrate the feasibility of the novel LLSME method. The extraction parameters such as the organic solvent, extraction and desorption time were investigated. Comparison of the LLSME technique was made with molecularly imprinted polymer based solid-phase microextraction (MIP-SPME) and hollow fiber membrane-based liquid-phase microextraction (HF-LPME), respectively. The LLSME, integrating the advantages of high selectivity of MIP-SPME and enrichment and sample cleanup capability of the HF-LPME into a single device, is a promising sample preparation method for complex samples. Moreover, the new technique overcomes the problem of disturbance from water when the MIP-SPME fiber was exposed directly to aqueous samples. Applications to analysis of triazine herbicides in sludge water, watermelon, milk and urine samples were evaluated to access the real sample application of the LLSME method by coupling with high-performance liquid chromatography (HPLC). Low limits of detection (0.006–0.02 μg L−1), satisfactory recoveries and good repeatability for real sample (RSD 1.2–9.6%, n = 5) were obtained. The method was demonstrated to be a fast, selective and sensitive pretreatment method for trace analysis of triazines in complex aqueous samples.
Co-reporter:Yuling Hu, Ruijin Liu, Yi Zhang, Gongke Li
Talanta 2009 Volume 79(Issue 3) pp:576-582
Publication Date(Web):15 August 2009
DOI:10.1016/j.talanta.2009.04.029
In this study, a novel and simple dual-phase solvent system for the improvement of extraction capability of magnetic molecularly imprinted polymer (MIP) beads in aqueous sample was proposed. The method integrated MIP extraction and micro-liquid–liquid extraction (micro-LLE) into only one step. A magnetic MIP beads using atrazine as template was synthesized, and was applied to aqueous media by adding micro-volume of n-hexane to form a co-extraction system. The magnetic MIP beads preferred to suspend in the organic phase, which shielded them from the disturbance of water molecule. The target analytes in the water sample was extracted into the organic phase by micro-LLE and then further bound to the solid-phase of magnetic MIP beads. The beads specificity was significantly improved with the imprinting efficiency of template increasing from 0.5 to 4.4, as compared with that in pure aqueous media. The extraction capacity, equilibration process and cross-selectivity of the MIP dual-phase solvent extraction system were investigated.The proposed method coupled with high-performance liquid chromatography was applied to the analysis of atrazine, simazine, propazine, simetryn, prometryne, ametryn and terbutryn in complicated sample such as tomato, strawberry juice and milk. The method is selective, sensitive and low organic solvent-consuming, and has potential to broaden the range of MIP application in biological and environmental sample.
Co-reporter:Yuling Hu, Yifeng Fan, Zelin Huang, Chaoyong Song and Gongke Li
Chemical Communications 2012 - vol. 48(Issue 33) pp:NaN3968-3968
Publication Date(Web):2012/02/27
DOI:10.1039/C2CC17048E
In this work we demonstrated a facile method for in situ fabrication of the Fe3+–1,3,5-benzenetricarboxylic acid (BTC) metal–organic coordination polymer gel in a capillary, which was efficiently applied to the online enrichment of trace polycyclic aromatic hydrocarbons (PAHs) in environmental water and amphetamines drugs in urine.
Co-reporter:
Analytical Methods (2009-Present) 2015 - vol. 7(Issue 15) pp:NaN6108-6108
Publication Date(Web):2015/06/15
DOI:10.1039/C5AY01272D
Inspired by the bioadhesive and redox properties of the 3,4-dihydroxy-phenylalanine (DOPA) contained in marine mussels, a facile, rapid and economic colorimetric strategy for Hg2+ detection was developed. The abundant catechol chains on the surface of Ag@DOPA can reduce Hg2+ to Hg0 and form a Ag@DOPA@Hg nanostructure with the deposition of Hg0. The nanostructures of Ag@DOPA and Ag@DOPA@Hg were confirmed by X-ray photoelectron spectroscopy, transmission electron microscopy, elemental mapping and Fourier transform infrared spectroscopy. The formation of the Ag@DOPA@Hg nanostructure causes a change in the color of the Ag@DOPA colloids from golden yellow to purple blue, making it directly possible to detect Hg2+ using a colorimetric strategy within 5 minutes. With increasing concentrations of Hg2+ from 10 nM to 4 μM, the surface plasmon resonance absorbance peak of the Ag@DOPA colloids decreased in intensity and exhibited a good linear relationship with the Hg2+ concentration. The limit of detection was determined as 5 nM. Furthermore, this response was found to be highly selective for Hg2+ as the absorption spectrum was not affected by other metal ions such as Pb2+, Cr3+, Cu2+, Al3+, Ni2+, Co2+, etc. The excellent stability, selectivity and sensitivity of this strategy offer analytical practicability for Hg2+ detection in real water samples with recoveries in the range of 104–105% and cosmetic samples with recoveries in the range of 85–103%.
Co-reporter:
Analytical Methods (2009-Present) 2013 - vol. 5(Issue 18) pp:
Publication Date(Web):
DOI:10.1039/C3AY40745D
A selective, water-compatible and disposable complex imprinted polymer (CIP) membrane was prepared for L-phenylalanine detection combined with solid phase fluorescence detection. L-Phenylalanine coordinated with aluminum(III) acted as a complex template. The solid phase fluorescent signal was monitored to quantify L-phenylalanine after in situ derivatization with o-phthalaldehyde. Several parameters determining the performance of the CIP membrane were studied and optimized. The resulting CIP membrane exhibited good fluorescent response and selectivity towards L-phenylalanine in aqueous environments. The linear response of the CIP membrane to L-phenylalanine was in the range of 5.0–100 μmol L−1 with a limit of detection of 0.90 μmol L−1. The prepared CIP membrane was successfully applied in the analysis of L-phenylalanine in drinks and human urine with recoveries of 83.5–101.3% and RSDs ranging from 7.2% to 9.5%. The proposed method was compared with a high performance liquid chromatography method. The results showed that the developed method has satisfactory sensitivity, accuracy and precision for the selective determination of L-phenylalanine in water-abundant systems.
