Co-reporter:Zhaofu Fu, Wanting Huang, Gongke Li, Yufei Hu
Journal of Pharmaceutical Analysis 2017 Volume 7, Issue 4(Volume 7, Issue 4) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.jpha.2017.05.005
A novel flow-injection chemiluminescence (FI-CL) method free of CL reagent was developed for the determination of captopril based on its enhancing effect on the CL derived from diperiodatoargentate(III)-sulfuric acid system. Compared with the conventional CL system, the CL system based on trivalent silver was characterized of good selectivity for the absence of CL reagent. The CL mechanism was discussed through CL spectra and UV–vis absorption spectra. The conditions of the FI-CL system were investigated and optimized. Under the optimal conditions, the relative CL intensity was linear with the captopril concentration in the range of 0.3–15.0 μg/mL. The detection limit for captopril was 0.05 μg/mL, and the relative standard deviation (n=11) was 2.0% for 5.0 μg/mL captopril. The proposed method was applied to the analysis of captopril in tablet and human urine with the recoveries of 83.1%–112.5%, and the relative standard deviations of 0.5%–4.4%. The results obtained by the proposed method agreed well with those obtained from HPLC method. The proposed method is fast, convenient, and cost-effective for the determination of captopril in medicine and biological samples.
Co-reporter:Xialin Luo, Gongke Li, Yufei Hu
Talanta 2017 Volume 165() pp:377-383
Publication Date(Web):1 April 2017
DOI:10.1016/j.talanta.2016.12.050
•A NH2-MIL-53(Al) polymer monolith column prepared by in situ polymerization.•The monolithic column showed high extraction capacity to estrogens.•An in-tube SPME for online coupled to HPLC method was developed.•The method applied to directly online sensitive analysis of estrogens in urine.In this work, a novel NH2-MIL-53(Al) incorporated poly(styrene-divinylbenzene-methacrylic acid) (poly(St-DVB-MAA)) monolith was prepared via chemical fabrication. Moreover, it has been efficiently applied to the in-tube solid-phase microextraction (SPME) for online coupling with high-performance liquid chromatography (HPLC) to the direct determination of five estrogens in human urine samples. The NH2-MIL-53(Al)-polymer monolith was suitable for in-tube SPME owing to its good permeability, high extraction efficiency, chemical stability, good reproducibility and long lifetime. The extraction conditions including extraction solvent, pH of sample solution, flow rate of extraction and desorption, and desorption volume were investigated. Under the optimum conditions, the enrichment factors were 180–304 and saturated amounts of extraction were 2326–21393 pmol for estriol, 17β-estradiol, estrone, ethinyl estradiol and progesterone, respectively. The adsorption mechanism was also explored which contributed to its strong extraction to target compounds. The proposed method had low limit of detection (2.0–40 ng/L) and good linearity (with R2 between 0.9908 and 0.9978). Four endogenous estrogens were detected in urine samples and the recoveries of all five analytes were ranged from 75.1–120% with relative standard deviations (RSDs) less than 8.7%. The results showed that the proposed online SPME-HPLC method based on NH2-MIL-53(Al)-polymer monolithic column was highly sensitive for directly monitoring trace amount of estrogens in human urine sample.
Co-reporter:Runkun Zhang, Gongke Li, and Yufei Hu
Analytical Chemistry 2015 Volume 87(Issue 11) pp:5649
Publication Date(Web):April 27, 2015
DOI:10.1021/acs.analchem.5b00722
To study the interesting chemical reaction phenomenon can greatly contribute to the development of an innovative analytical method. In this paper, a simple CL reaction cell was constructed to study the chemiluminescence (CL) emission from the thermal oxidation of carbon disulfide (CS2). We found that the CL detection of CS2 exhibits unique characteristics of excellent selectivity and rapid response capacity. Experimental investigations together with theoretical calculation were performed to study the mechanism behind the CL reaction. The results revealed that the main luminous intermediates generated during the thermal degradation of CS2 are SO2* and CO2*. Significantly, this CL emission phenomenon has a wide application due to many sulfur-containing compounds that can convert to CS2 under special conditions. On the basis of this scheme, a CS2-generating and detection system was developed for rapid measurement of CS2 or other compounds that can convert to CS2. The usefulness of the system was demonstrated by measuring dithiocarbamate (DTC) pesticides (selected mancozeb as a representative analyte) based on the evolution of CS2 in spiked agricultural products. Results showed that the system allows online and large volume detection of CS2 under nonequilibrium condition, which greatly reduces the analytical time. The concentrations of mancozeb in the spiked samples were well-quantified with satisfied recoveries of 76.9–97.3%. The system not only addresses the urgent need for rapid in-field screening of DTC residues in foodstuffs but also opens a new opportunity for the fast, convenient, and cost-effective detection of CS2 and some other sulfur-containing compounds in complex samples.
Co-reporter:Su Yao, Yufei Hu, Gongke Li
Electrochimica Acta 2015 Volume 155() pp:305-311
Publication Date(Web):10 February 2015
DOI:10.1016/j.electacta.2014.12.151
A flowing electrolytic device equipped with large electrode area and high electric field intensity was designed for the preparation of fluorescent carbon nanoparticles (CNPs) and carbon nanosheets (CNSs). Comparing with normal electrolysis, the flowing electrolysis showed higher efficiency for the preparation and separation of the products. In the high intensity electric field, the CNPs and CNSs were enriched to the flowing electrolyte and the anode surface respectively. The obtained CNPs were regarded as a fluorescent probe of Fe3+, and the CNSs modified electrode was fabricated to be an electrochemical sensor of acetaminophen for its electrocatalytic properties. So the CNPs and CNSs were expected for the application of fluorescent and electrochemical detection.
Co-reporter:Zhaofu Fu, Gongke Li and Yufei Hu
Analytical Methods 2015 vol. 7(Issue 11) pp:4590-4595
Publication Date(Web):22 Apr 2015
DOI:10.1039/C5AY00447K
In this paper, a novel flow-injection chemiluminescence method was developed for the determination of indole-3-acetic acid (IAA). The chemiluminescence signal from the reaction of an Ag(III) complex and a sulfuric acid system was enhanced in the presence of IAA. The conditions of the CL system were investigated and optimized. Under the optimal conditions, the relative chemiluminescence intensity was linear with the IAA concentration in the range of 1.0 × 10−10 g mL−1 to 1 × 10−8 g mL−1. The detection limit for IAA was 7.7 × 10−11 g mL−1, and the relative standard deviation (n = 11) was 0.5%. The proposed method was applied to the analysis of IAA in human urine, mung bean sprouts and soil samples with recoveries of 103.5–117.1%, 87.0–98.4% and 94.1–118.8%, respectively, and the relative standard deviations was 0.6–2.7%. The results obtained by the proposed method agreed well with those obtained from the HPLC method. The chemiluminescence mechanism is discussed by comparison of fluorescence spectra and the UV-vis absorption spectra.
Co-reporter:Yahong Chen, Gongke Li and Yufei Hu
Analytical Methods 2015 vol. 7(Issue 5) pp:1971-1976
Publication Date(Web):08 Jan 2015
DOI:10.1039/C4AY02843K
In this paper, a novel electrochemical method is proposed for the determination of 5-hydroxytryptophan (5-HTP) based on a carbon nanosheets (CNSs)-modified electrode. The CNSs were prepared by a one-step flowing electrolysis using a home-made device. The surface morphology and composition of the CNSs were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The cyclic voltammetry method was used to study the electrochemical behavior of 5-HTP on the CNSs-modified electrode. The results suggested that the modified electrode exhibited high electrocatalytic activity, and that the anodic peak current of 5-HTP was significantly enhanced on the modified electrode. A differential pulse voltammetry method was developed for the determination 5-HTP at the modified electrode. In the optimum experimental conditions, the linear calibration range varied from 5 × 10−8 mol L−1 to 1 × 10−6 mol L−1, with a detection limit of 3 × 10−8 mol L−1. The proposed method was further successfully applied for the determination of 5-HTP in rats' brain tissue samples, with the recovery ranging from 90.3% to 98.0%.
Co-reporter:Runkun Zhang, Yufei Hu, and Gongke Li
Analytical Chemistry 2014 Volume 86(Issue 12) pp:6080
Publication Date(Web):May 19, 2014
DOI:10.1021/ac5012359
In this paper, we described a new concept of cyclic chemiluminescence (CCL) detection, and a homemade system was designed to realize such detection. The direction of the carrier in the CCL system is in a state of periodical change that can trigger a succession of chemiluminescence (CL) reactions in a single sample injection. Therefore, in contrast to the traditional CL detection, which only records a single signal, CCL allows us to obtain multistage signals. To evaluate the new method, the cataluminescence (CTL) reaction of the volatile organic compounds (VOCs) on a nanosized catalyst was selected as the analytical model. We found that each CCL reaction has a unique exponential decay equation (EDE) to describe the change law of its multistage signals. Further study showed that the initial amount (A) of the EDE is linear with the analyte concentration, while the decay coefficient (k) is a characteristic constant for a given reaction. The formation mechanism of the exponential function and the determinants of the decay coefficient were discussed in detail. As a distinct application, CCL is capable of rapidly discriminating various analytes and even structural isomers.
Co-reporter:Su Yao, Yufei Hu, Gongke Li
Carbon 2014 Volume 66() pp:77-83
Publication Date(Web):January 2014
DOI:10.1016/j.carbon.2013.08.044
A simple and efficient sonoelectrochemical method was proposed for the preparation of blue fluorescent carbon nanoparticles (CNPs) in pure water. Benefiting from the combination of the high intensity electric field and the ultrasonic field, pure blue fluorescent CNPs were rapidly generated without any complex purification. The obtained CNPs possess excellent fluorescent property and thermodynamic stability in aqueous solution. The effects of the high intensity electric field and the ultrasonic field on the fluorescent property of the electrolytic products were also investigated. Compare to the normal electrolysis, the high intensity electric field played a crucial role in improving the product purity. On the other hand, the electrolytic efficiency was obviously enhanced, since the ultrasonic field could act synergistically with the high intensity electric field. The obtained CNPs have the potential for application in bioimaging, immuno-labeling and fluorescence detection.
Co-reporter:Xiaoting Yang, Yufei Hu, Gongke Li
Journal of Chromatography A 2014 Volume 1342() pp:37-43
Publication Date(Web):16 May 2014
DOI:10.1016/j.chroma.2014.03.041
•A boronate affinity monolithic column was prepared by in situ polymerization.•The monolithic column showed high extraction capacity to four monoamines.•An online micro-solid-phase extraction coupled with HPLC method was developed.•The method was successfully applied to online analysis of monoamines in human urine.Quantification of monoamine neurotransmitters is very important in diagnosing and monitoring of patients with neurological disorders. We developed an online analytical method to selectively determine urinary monoamine neurotransmitters, which coupled the boronate affinity monolithic column micro-solid-phase extraction with high-performance liquid chromatography (HPLC). The boronate affinity monolithic column was prepared by in situ polymerization of vinylphenylboronic acid (VPBA) and N,N′-methylenebisacrylamide (MBAA) in a stainless capillary column. The prepared monolithic column showed good permeability, high extraction selectivity and capacity. The column-to-column reproducibility was satisfactory and the enrichment factors were 17–243 for four monoamine neurotransmitters. Parameters that influence the online extraction efficiency, including pH of sample solution, flow rate of extraction and desorption, extraction volume and desorption volume were investigated. Under the optimized conditions, the developed method exhibited low limit of detection (0.06–0.80 μg/L), good linearity (with R2 between 0.9979 and 0.9993). The recoveries in urine samples were 81.0–105.5% for four monoamine neurotransmitters with intra- and inter-day RSDs of 2.1–8.2% and 3.7–10.6%, respectively. The online analytical method was sensitive, accurate, selective, reliable and applicable to analysis of trace monoamine neurotransmitters in human urine sample.
Co-reporter:Qisheng Zhong;Gongke Li
Journal of Separation Science 2013 Volume 36( Issue 24) pp:3903-3910
Publication Date(Web):
DOI:10.1002/jssc.201300874
An online system that can perform dynamic microextraction, on-coating derivatization and desorption, and subsequent GC–MS analysis with a large-volume injection was developed. A derivatization cell as the conjunction of the online system was developed for the online extraction and derivatization. To evaluate the feasibility of the online system, methyltestosterone molecularly imprinted polymer filaments (MIPFs) were prepared for the selective online extraction of five androgenic steroids, namely, methyltestosterone, testosterone, epitestosterone, nandrolone, and metandienone. Under the optimized conditions, the detection limits of testosterone and epitestosterone were 0.09 and 0.12 μg/L, respectively, which were under the minimum required performance limits between 2 and 10 μg/L from the World Anti-Doping Agency. The detection limits of the other three androgenic steroids were varied from 0.04 to 0.18 μg/L. Finally, the MIPFs–GC–MS method was applied for the determination of androgenic steroids in urine, and satisfactory recovery (78.0–96.9%) and reproducibility (3.2–8.9%) were obtained. The proposed online coupling system offers an attractive alternative for hyphenation to GC instruments and could also be extended to other adsorptive materials.
Co-reporter:Su Yao, Yufei Hu, Gongke Li, Yukui Zhang
Electrochimica Acta 2012 Volume 77() pp:83-88
Publication Date(Web):30 August 2012
DOI:10.1016/j.electacta.2012.05.078
In this paper, carbon nanoparticle (CNP) with abundant oxygen-containing groups was prepared. The adsorption behavior of ractopamine on the CNP surface was investigated by electrochemical study. Two oxidative peaks of ractopamine were observed at 0.60 and 0.82 V. The oxidative peaks were distinctly enhanced on the CNP surface and the enhancements were result from the adsorption. The adsorption mechanism was discussed in detail and deduced to be via π–π interaction and salt linkage. The salt linkage between the secondary amide of ractopamine and the carboxyl group on CNP surfaces was confirmed. It provided a novel electron transfer channel for the electrochemical oxidation of phenolic groups. A sensitive differential pulse voltammetry method based on the adsorption was proposed for the determination of ractopamine with the detection limit of 2.0 × 10−10 mol L−1. This method was successfully applied to the analysis of ractopamine in urine sample.
Co-reporter:Qisheng Zhong, Yufei Hu, Yuling Hu, Gongke Li
Journal of Chromatography A 2012 Volume 1241() pp:13-20
Publication Date(Web):8 June 2012
DOI:10.1016/j.chroma.2012.04.017
A novel sample preparation technique termed dynamic liquid–liquid–solid microextraction (DLLSME) was developed and on-line coupled to high performance liquid chromatography (HPLC) for direct extraction, desorption, and analysis of trace estrogens in complex samples. The DLLSME consists of the aqueous donor phase, the organic medium phase and the molecularly imprinted polymer filaments (MIPFs) as solid acceptor phase. The organic solvent with lesser density was directly added on top of the aqueous sample, and the dynamic extraction was performed by circulating the organic solvent through the MIPFs inserted into a PEEK tube which served as an extraction and desorption chamber. Afterwards, the extracted analytes on the MIPFs were on-line desorbed and then introduced into the HPLC for analysis. To evaluate the feasibility of the on-line system, a new DLLSME-HPLC method was developed for the analysis of five estrogens in aqueous samples by using 17β-estradiol MIPFs as the solid phase. Under the optimized conditions, the enrichment factors of 51–70, limits of detection of 0.08–0.25 μg/L and precision within 4.5–6.9% were achieved. Furthermore, the proposed method was applied to the analysis of real samples including urine, milk and skin toner, satisfactory recovery (81.9–99.8%) and reproducibility (4.1–7.9%) were obtained. Especially, 0.59 μg/L of 17β-estradiol was determined in female urine sample. The DLLSME offers an attractive alternative for direct analysis of trace analytes in aqueous samples and could potentially be extended to other adsorptive materials.Highlights► Dynamic liquid–liquid–solid microextraction (DLLSME) was originally developed. ► DLLSME based on molecularly imprinted polymeric filaments as solid acceptor phase. ► DLLSME on-line coupled to HPLC for direct analysis of trace estrogens.
Co-reporter:Qisheng Zhong;Yuling Hu ;Gongke Li
Journal of Separation Science 2012 Volume 35( Issue 23) pp:3396-3402
Publication Date(Web):
DOI:10.1002/jssc.201200548
Based on a special homemade interface, the molecularly imprinted stir bar sorptive extraction was coupled to high performance liquid chromatography for the online desorption and analysis. During desorption, the analytes desorbed from stir bar were delivered to a sample loop and then was introduced into liquid chromatography for further analysis. The online desorption and introduction processes were real-time monitored by the ultraviolet detector of the liquid chromatography system. In this way, the method sensitivity and reproducibility was improved for the introduction timing of the desorption solvent with greatest concentration of the target analytes was accurately controlled. To demonstrate the feasibility of the method, terbuthylazine imprinted stir bar was synthesized and used for the analysis of nine triazines in rice. Under the optimized conditions, limits of detection of 0.02–0.11 μg/L and precision within 4.3–7.2% were achieved. The new method was compared with other two traditional offline desorption procedures, i.e. ultrasonic-assisted desorption and static thermal desorption. The comparison results showed that the proposed method is accurate, precise, fast, and suitable for the trace analysis of complex samples.
