[Show abstract][Hide abstract] ABSTRACT: Valnemulin, a semisynthetic pleuromutilin derivative related to tiamulin, is broadly used to treat bacterial diseases of animals. Despite its widespread use, metabolism in animals has not yet been fully investigated. To better understand valnemulin biotransformation, in this study, metabolites of valnemulinin in in vitro and in vivo rats, chickens, swines, goats and cows were identified and elucidated using ultra-performance liquid chromatography-quadrupole/time-of-flight hybrid mass spectrometry (UPLC-Q/TOF-MS). As a result, there were totally 7 metabolites of valnemulin identified in vitro, and 75, 61 and 74 metabolites detected in in vivo rats, chickens and swines, respectively, and the majority metabolites were reported for the first time. The main metabolic pathways of valnemulin were found to be hydroxylation in the mutilin-part (the ring system) and the side chain, oxidization on the sulphur of the side chain to form S-oxides, hydrolysis of the amido bond and acetylization in the amido of the side chain. In addition, hydroxylation in the mutilin-part was proposed to be the primary metabolic route. Furthermore, the results revealed that the 2β-hydroxy-valnemulin (V1) and 8α-hydroxy-valnemulin (V2) were the major metabolites for rats and swines and S-oxides (V6) in chickens.
Journal of agricultural and food chemistry. 08/2014;
[Show abstract][Hide abstract] ABSTRACT: Quinoxaline feed additives are antimicrobial growth promoters (AGPs); use three of them is permitted, and two of them are illegally used. It results in residue of quinoxaline AGPs and their metabolites in edible animal tissues, which are potentially harmful to human health. In order to effectively monitor the multiple residues of them in swine liver, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) was developed based on polyclone antibody preparation. Protein conjugates were synthesized and immune to New Zealand white rabbit according to designed schemes. The effective antiserum with 50 % inhibiting concentration (IC50) value of 1.34 μg L−1 was obtained. A new synthesized quinoxaline with similar chemical structure to olaquindox but longer spacer arm was used as coating antigen. Cross-reactivity of other four quinoxaline AGPs and their eight metabolites was tested; seven of them have cross-reactivity over 10 %, with IC50 of 0.10–2.50 μg L−1. At the spike level of 1 to 100 μg kg−1 in swine liver, the recoveries of all compounds ranged from 80.14 % to 96.90 %, with the inter-day variation coefficient (CV) of 5.67–13.82 % and the intra-assay CV of 6.22–14.19 %. The limit of detection ranged from 0.03 ± 0.002 to 0.79 ± 0.05 μg L−1. Positive samples were determined by the ic-ELISA method and successfully confirmed by liquid chromatography-tandem mass spectrometry. The proposed ELISA is feasible for screening quinoxaline AGPs and their metabolites in swine liver.
[Show abstract][Hide abstract] ABSTRACT: A gas chromatographic-tandem mass spectrometric method (GC-MS/MS) has been developed for sensitive and reliable detection of 8 organochlorine pesticide residues in wild L. chuanxiong and chestnut. The target compounds were extracted from both samples and simultaneously rudely cleaned up by water-acetone and dichloromethane. Then, the obtained dichloromethane phase was evaporated to dry, treated with H2SO4, centrifuged, evaporated and redissolved in 0.5 mL of benzene for GC-MS/MS detection. When spiked from 5 to 500 μg/kg, the average recoveries of organochlorine pesticides in two kinds of sample ranged from 74.2 to 110.9% with the intra-day RSD of 0.1 to 10.1% and the inter-day RSD of 0.7 to 10.5%. The limit of detection of eight compounds varied from 0.13 to 1.2 μg/kg in two kinds of samples.
Journal of Analytical Chemistry 03/2013; 68(3). · 0.62 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Methyl-3-quinoxaline-2-carboxylic acid (MQCA) is a possible residue marker for three quinoxaline veterinary medicines (olaquindox, mequindox, and quinocetone). The wide application of mequindox/quinocetone or the illegal use of olaquindox leads to MQCA residue in animal's original food, thereby threatening the safety of human food. The indirect competitive enzyme-linked immunosorbent assay (IC-ELISA) with a specific coating antigen and monoclonal antibody (MAB) was established and optimized for detecting MQCA in swine liver. Samples were acidified with 2 mol l(-1) hydrochloric acid, extracted with ethyl acetate-hexane-isopropanol (8 + 1 + 1, v/v/v) and then detected by IC-ELISA. The logarithm correlation of standards to OD values ranged from 0.2 to 200 μg l(-1), with IC(50) of 6.46 μg l(-1). Negligible cross-reactivity happened to five quinoxaline antibiotics (olaquindox, mequindox, quinocetone, carbadox, and cyadox) and the metabolite of carbadox and cyadox (quinoxaline-2-carboxylic acid). When spiked with 1 to 100 μg kg(-1) of MQCA, the recoveries ranged from 85.44 to 100.02 %, with the intra-assay coefficient of variation (CV) of 6.64-10.57 % and inter-assay CV of 7.29-10.88 %. The limit of detection for MQCA was 1.0 μg kg(-1) in swine liver. Furthermore, incurred samples were detected by the IC-ELISA and then conformed by a reported LC/MS/MS method, it shown that there was good correlation between the two methods. All these results indicated that the IC-ELISA method is appropriate for surveillance MQCA residue in animal tissues.
Analytical and Bioanalytical Chemistry 01/2013; · 3.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed for the determination of mequindox (MEQ) and its two metabolites (1-desoxymequindox and 1, 4-bisdesoxymequindox, 1-DMEQ and BDMEQ) in swine liver. This method was validated on the basis of Commission Decision 2002/657/EC. Target analytes were extracted from swine liver with acid acetonitrile, purified by an Oasis MAX cartridge, and separated by UPLC. The chromatography total time was less than 8 min with gradient elution of 0.1% formic acid in methanol. Data acquisition was carried out by electrospray ionization tandem mass spectrometry (ESI/MS/MS) operated in a multiple reaction monitoring mode. At fortified levels from 2 to 100 μg kg−1 in swine liver, recoveries of target analytes ranged from 80% to 85% with the intra-day coefficient of variation (CV) being ≤ 14.48% and inter-day CV ≤ 14.53%, respectively. The limit of detection (LOD) ranged from 0.58 to 1.02 μg kg−1 and the limit of quantification (LOQ) range was 1.93 to 3.40 μg kg−1 for each analyte. The result indicated that this method was specific, sensitive, and suitable for the quantification and conformation of MEQ and its two metabolites in swine liver.
[Show abstract][Hide abstract] ABSTRACT: A rapid and sensitive ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed for the determination of cyadox (CYX) and its three major metabolites, quinoxaline-2-carboxylic acid (QCA), 1-desoxycyadox (1-DCYX) and 1,4-bisdesoxycyadox (BDCYX) in fish. Samples were extracted with acetonitrile–0.5 M hydrochloric acid (9 + 1) and cleaned up using Oasis MAX cartridges. The total time taken for separation by UPLC was less than 5 min. The four target compounds were then determined by ESI-MS/MS. At the fortified levels of 2–50 μg kg−1 in fish, recoveries of all the compounds ranged from 80.2% to 88.2%, with a relative standard deviation of 6.8 to 14.6%. Limits of detection for CYX, QCA, 1–DCYX and BDCYX were 0.52, 1.07, 0.69 and 0.38 μg kg−1, respectively.
[Show abstract][Hide abstract] ABSTRACT: An ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/ MS) method was established for the determination of 3-methyl-quinoxaline-2-carboxylic acid (MQCA) in animal tissues and aquatic products. The analyte was extracted with 0.2 mol/L hydrochloric acid. The extract was cleaned up on a Bond Elut C18 cartridge. Then the eluate was collected and evaporated to dryness under nitrogen gas at 35 degrees C. The residue was redissolved in acetonitrile containing 0.1% (v/v) formic acid. The identification was performed by multiple reaction monitoring in positive electrospray ionization. The quantification was done by external standard method. The calibration curves showed good linearity within the range of 2-500 microg/L with the correlation coefficients (r2) greater than 0.990. The limits of detection (LODs) of MQCA in pork, swine liver, pig kidney, fish, prawn, and crab were 0.90, 1.51, 0.94, 1.04, 1.62 and 1.80 microg/kg, respectively; and the limits of quantification (LOQs) were 3.00, 5.02, 3.13, 3.46, 5.40 and 6.00 microg/kg, correspondingly. The recoveries of MQCA in animal tissues and aquatic products were 73.6%-89.0% at the spiked levels of 3-100 microg/kg. The intra-day relative standard deviations (RSDs, n = 5) were less than 15%, and inter-day RSDs (n = 3) were less than 20%. The results demonstrated that the sensitivity, accuracy, and precision were fit for the requirements of veterinary drug residue analysis.
Se pu = Chinese journal of chromatography / Zhongguo hua xue hui 01/2012; 30(1):45-50.
[Show abstract][Hide abstract] ABSTRACT: A rapid and sensitive method based on competitive indirect enzyme-linked immunosorbent assay (ciELISA) was developed and validated for the detection of DON (deoxynivalenol) in cereals with the confirmation of the reliable ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Within this method, the IC50 (half maximal inhibitory concentration of a substance) of the DON-specific monoclonal antibody (MAb) we produced was 61.10 ng/mL. The limit of detection (LOD) value, measured by IC10, was 6.12 ng/mL, which is below the maximum residue levels (MRLs) established for DON in various cereals. In spiked samples, the recoveries ranged from 79.3% to 115.2% for maize and from 74.3% to 118.3% for wheat. This method was compared with the UPLC-MS/MS method by testing four concentrations. The correlation coefficient for the two methods was 0.9884 in a linear-regression analysis. The results illustrated the reliability of the ciELISA method for the determination of cereal samples.
Food and Agricultural Immunology 01/2012; 23(1):41-49. · 0.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: With the profile of ultra-performance liquid chromatography/electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC/ESI-QTOF-MS), the metabolites of quinocetone (QCT) in swine were identified and investigated. On the basis of finding, the biodistribution and elimination characters of them were revealed. Through data-dependent acquisition ways, both MS and MS/MS scans of metabolites were simultaneously acquired on the same sample injection. The metabolites were reliably characterized by their accurate MS/MS spectra and their different fragmentation pathways. A total of 42 metabolites were found in swine, 11 (Q32-Q42) of them were identified to be novel in vivo. The results demonstrated that QCT was extensively metabolized and distributed in vivo, especially in gastrointestinal tract. The reductions of the N → O group, carbonyl, double-bond in QCT were the main metabolic pathways observed in swine. Elimination of the four major metabolites (Q1, Q2, Q7, Q39) of QCT suggest that QCT was mainly metabolized at 12 h in swine, then excreted gradually together with its main metabolites after that. QCT and its major metabolites are excreted more and more rapidly in swine liver, kidney and muscle, respectively. It afforded prima research of QCT metabolism in vivo of swine and given an important basis for further study of its toxicological safety evaluation and marker residue finding.
European Journal of Drug Metabolism and Pharmacokinetics 09/2011; 37(2):141-54. · 1.31 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The molecular recognition of hapten-antibody is a fundamental event in competitive immunoassay, which guarantees the sensitivity and specificity of immunoassay for the detection of haptens. The aim of this study is to investigate the correlation between binding ability of one monoclonal antibody, 1H9B4, recognizing and the molecular aspects of α-zearalanol analogs. The mouse-derived monoclonal antibody was produced by using α-zearalanol conjugated to bovine serum albumin as an immunogen. The antibody recognition abilities, expressed as IC(50) values, were determined by a competitive ELISA. All of the hapten molecules were optimized by Density Function Theory (DFT) at B3LYP/ 6-31G* level and the conformation and electrostatic molecular isosurface were employed to explain the molecular recognition between α-zearalanol analogs and antibody 1H9B4. Pearson Correlation analysis between molecular descriptors and IC(50) values was qualitatively undertaken and the results showed that one molecular descriptor, surface of the hapten molecule, clearly demonstrated linear relationship with antibody recognition ability, where the relationship coefficient was 0.88 and the correlation was significant at p < 0.05 level. The study shows that computational chemistry and Pearson Correlation analysis can be used as tool to help the immunochemistries better understand the processing of antibody recognition of hapten molecules in competitive immunoassay.
Journal of Molecular Recognition 08/2011; 24(5):815-23. · 3.01 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new method using ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS) was developed for determination of quinocetone (QCT) and its major metabolites, 1–desoxyquinocetone (1–DQCT), 4–desoxyquinocetone (4–DQCT), 1,4–bisdesoxyquinocetone (DQCT) and ethyl–3–quinoxaline–2–carboxylicacid (MQCA) in swine liver. Tissue samples were extracted by a two-step method. Firstly, all analytes except MQCA were extracted with ethyl acetate. Then a hydrochloric acid solution was added in the remained sediment for hydrolysis of combined MQCA. The MQCA in the acid extract was transferred to ethyl acetate by liquid-liquid extraction (LLE) approach. All the ethyl acetate extract were combined, evaporated, resolved in a phosphate buffer, and cleaned up using a Oasis MAX cartridges. The chromatographic separation of all the analytes was achieved in less than 5 min using UPLC. The identification and confirmation by accurate mass measurement and their different fragmentation pathways were performed on ESI-Q-TOF-MS (MS/MS). The quantitation was carried out in TOF mode using narrow window extracted ion chromatogram of each compound. In the range of 1-100 µg·kg–1, the calibration curve equations of MQCA, QCT, 4-DQCT, 1-DQCT and DQCT were y=0.7878x+10.49, y=4.656x+42.244, y=5.5825x+24.919, y=8.491x+21.195 and y=10.733x+160.72, respectively. And the relative coefficients of all calibration curves were higher than 0.98. The limit of detection and the limit of quantification were 1.4–4.8 µg·kg–1 and 4.6–15.9 µg·kg–1, respectively. The established method was validated for determination of incurred swine liver samples in an actual residue study.
Journal of Analytical & Bioanalytical Techniques. 11/2010; 01(03):1000108.
[Show abstract][Hide abstract] ABSTRACT: A fluorescence polarization immunoassay (FPIA) for the determination of salinomycin (SAL) was developed by using anti-SAL
monoclonal antibodies (mAb). Fluorescein labeled SAL (tracer) was synthesized by the N-hydroxysuccinimide active ester method
and purified using thin layer chromatography (TLC). The developed FPIA for SAL had a dynamic range from 0.60 to 2193 ng/mL
with an IC50 value of 33.2 ng/mL and a detection limit (LOD) of 0.08 ng/mL. No significant cross-reactivities were observed with other
drugs but 67.6% with narasin.
Keywordssalinomycin-tracer-fluorescence polarization immunoassay-monoclonal antibody
[Show abstract][Hide abstract] ABSTRACT: A robust, reliable and sensitive method is described for the simultaneous determination of diazepam, methaqualone, chlorpromazine
and promethazine in swine muscle and liver tissues by GC–MS. The analytes were extracted with ethyl acetate and further clean-up
performed with MCX solid-phase extraction cartridges. LODs and LOQs in the two tissues ranged from 0.2 to 0.3μgkg−1 and 0.5 to 1μgkg−1, respectively. Mean recoveries for the analytes ranged between 87.6 and 106.8%.
[Show abstract][Hide abstract] ABSTRACT: A method was developed to simultaneously detect six resorcylic acid lactones in feed by GC–MS. Samples were extracted with
methanol followed by a two step liquid–liquid extraction and an HLB SPE clean-up. The samples were derivatized with BSTFA + TMCS
(99/1; v/v) and determined by GC–MS. For all analytes, the ranges of recoveries were 81.2–98.2%, with RSDs of 3.2–15.2%, and the LODs
were 0.2–0.6 μg kg−1.
[Show abstract][Hide abstract] ABSTRACT: A liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI MS/MS) method for the determination of 5 polyether antibiotics (lasalocid, salinomycin, monensin, narasin and maduramicin) in chicken tissues was developed. The polyether antibiotics were extracted from chicken tissues with methanol. The extract was evaporated to dry, and redissolved in hexane, then cleaned up on a Sep-Pak Silica solid-phase extraction cartridge. The target drugs were eluted with 6 mL methylene chloride-methanol (90:10, v/v), and the eluate was collected and dried under a gentle stream of nitrogen gas, then the residue was dissolved with 1 mL acetonitrile (containing 0.1% formic acid) and analyzed by LC-MS/MS. The LC separation was performed on a Symmetry Shield reversed phase C18 bonded silica column with acetonitrile (containing 0.1% formic acid)-0.1% formic acid (97:3, v/v) as mobile phase. The quantification was carried out by positive electrospray ionization and multiple reaction monitoring (MRM) mode. The validation was carried out on spiked chicken muscle (spiked at 0.1 -1500 microg/kg) and chicken liver (spiked at 0.2-4500 microg/kg), the average recoveries of target drugs ranged from 71.6%-99.1% with intra-day relative standard deviations (RSDs) of 3.2%-10.7% and inter-day RSDs of 4.6%-14.7%. The limits of quantification (LOQs) in chicken muscle and liver were 0.1-1.0 kg/kg. The results demonstrated that the sensitivity, accuracy and precision of this method meet the requirements of veterinary drug residue analysis. The method is applicable to detect 5 polyether antibiotics in chicken muscle and liver.
Se pu = Chinese journal of chromatography / Zhongguo hua xue hui 11/2009; 27(6):815-9.
[Show abstract][Hide abstract] ABSTRACT: A rapid method has been developed for the determination of tiamulin (TML) residue in swine tissues by high performance liquid chromatography. The samples were extracted with phosphate buffer-ethyl acetate solution, and then centrifuged by 5000 rpm for 10 min, 0.1% fartrate solution was added in the supernatant obtained with liguid-liquid-liquid extraction, and the organic phase was eveporated. After fats having been removed with hexan, further purification was performed with Oasis HLB solid phase extraction column. The TML residue was determined by HPLC with a mobile phase of acetonitrile-0.0125% acetic acid(42:58, V/V) and UV detection at 210 nm. The average recovery rates of TML in pork and swine liver were in the range of 80.1% - 92.7% when spiked 25 - 500 mu g/kg. The RSD ranged from 2.0% to 13.9%. The detection limits were 5 mu g/kg and 8 mu g/kg for pork and swine liver, respectively.
[Show abstract][Hide abstract] ABSTRACT: The three-dimensional quantitative structure-activity relationship (3D-QSAR) model of sulfonamide analogs binding a monoclonal antibody (MabSMR) produced against sulfamerazine, was carried out by comparative molecular field analysis (CoMFA). The affinities of MabSMR, expressed as Log10IC50, for 17 sulfonamide analogs were determined by competitive fluorescence polarization immunoassay (FPIA). Removal of two outliers from the initial set of 17 sulfonamide analogs improved the predictability of the models. The 3D-QSAR model of 15 sulfonamides resulted in q2cv values of 0.600, and r2 values of 0.995, respectively. This novel study combining FPIA with CoMFA demonstrates that multidisciplinary research can be used as a useful tool to investigate antigen-antibody interactions and provide information required for design of novel haptens, which may result in new antibodies with properties already optimized by an antibody-based immunoassay.
[Show abstract][Hide abstract] ABSTRACT: A reliable and sensitive liquid chromatography–electrospray ionization-tandem mass spectrometry (LC–ESI-MS/MS) confirmation method has been developed for the simultaneous determination of chloramphenicol (CAP), thiamphenicol (TAP), florfenicol (FF), and florfenicol amine (FFA) in chicken muscle. Samples were extracted with basic ethyl acetate, defatted with hexane, and cleaned up on Oasis MCX cartridges. LC separation was achieved on a XTerra C18 column with gradient elution using a mobile phase composed of acetonitrile and water at a flow rate of 0.20 mL/min. The analysis was carried out on a triple–quadrupole tandem mass spectrometer in the multiple reaction monitoring (MRM) mode via electrospray interface operated in the positive and negative ionization modes, with deuterated chloramphenicol-d5 (d5-CAP) as the internal standard. The method validation was performed according to the criteria of Commission Decision 2002/657/EC. Four identification points were obtained for each analyte with one precursor ion and two product ions. Limits of detection (LODs) were 0.1 μg/kg for CAP, 0.2 μg/kg for FF and 1 μg/kg for TAP and FFA in chicken muscle. Linear calibration curves were obtained over concentration ranges of 0.3–20 μg/kg for CAP, 0.5–20 μg/kg for FF and 3–100 μg/kg for TAP and FFA in tissues. Mean recoveries of the 4 analytes ranged from 95.1% to 107.3%, with the corresponding intra- and inter-day variation (relative standard deviation, R.S.D.) less than 10.9% and 10.6%, respectively. The decision limit (CCα) and detection capability (CCβ) of the method were also reported.
Journal of Chromatography B 01/2008; · 2.49 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A rapid and sensitive gas chromatography method was developed for the simultaneous determination of florfenicol (FF) and its metabolite florfenicol amine (FFA) in fish, shrimp, and swine muscle. The extracted samples were defatted with hexane and cleaned up by solid-phase extraction using Oasis MCX cartridges. The eluate was evaporated to dryness, and residues were derivatized and determined by gas chromatography with a microcell electron capture detector. Overall average recoveries ranged from 81.7 to 109.7% for fish, 94.1 to 103.4% for shrimp, and 71.5 to 91.4% for swine muscle. The detection limit was 0.5 ng/g for FF and 1 ng/g for FFA, respectively. The method was validated for the determination of incurred swine muscle samples in an actual residue study.
Journal of AOAC International 01/2006; 89(5):1437-41. · 1.23 Impact Factor