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Shen C.-Y.,Jiangsu Entry Exit Inspection and Quarantine Bureau of PRC | Shen D.-X.,Nanjing University | Ding T.,Jiangsu Entry Exit Inspection and Quarantine Bureau of PRC | Xu J.-Z.,Jiangsu Entry Exit Inspection and Quarantine Bureau of PRC | And 3 more authors.
Journal of Liquid Chromatography and Related Technologies | Year: 2011

A new method based on liquid chromatography-tandem mass spectrometry has been developed for simultaneous determination of 14 quinolones (QNs) residues, including ciprofloxacin, danofloxacin, difloxacin, enoxacin, enrofloxacin, flumequine, lomefloxacin, marbofloxacin, norfloxacin, orbifloxacin, ofloxacin, pipemidic acid, pefloxacin, and sarafloxacin in royal jelly. The proposed analytical procedure involves extraction of the QNs from samples by 0.1M sodium hydroxide aqueous solution, a step for clean-up and preconcentration of the analytes by anion-exchange solid-phase extraction (SPE) and liquid chromatographic separation with mass spectrometric detection. Internal standard calibration was applied with norfloxacin-D5 as internal standard (I.S.). Satisfactory recovery (from 64% to 113%), excellent repeatability precision (relative standard deviations, RSDs below 6%), reproducibility precision (RSDs below 10%), and low limits of quantifications (LOQs from 0.3 to 2.5μgkg -1) were evaluated from spiked royal jelly samples at 2.5, 5.0, and 10.0μgkg -1 three concentration levels. This protocol has been validated by five authoritative laboratories and successfully used for analysis of a large number of import-export samples (n>2000). Norfloxacin and ciprofloxacin were found to be the most common contamination in royal jelly in the ranges of 3.5-30μgkg -1 and 4.5-20μgkg -1, respectively. Copyright © Taylor & Francis Group, LLC. Source

Cao X.-W.,Nanjing University | Shen W.-J.,Jiangsu Entry Exit Inspection and Quarantine Bureau of PRC | Zhu J.,Nanjing University | Zhang J.,Nanjing University | And 7 more authors.
Food Analytical Methods | Year: 2013

A gas chromatography-mass spectrometry (GC-MS) multi-residue method with different ionization modes has been developed for the determination of 23 organochlorine pesticides and ten polychlorinated biphenyls (PCBs) in crayfish. The approach was based on an extraction with acetonitrile saturated by hexane (containing 0. 1 % acetic acid), followed by a dispersed solid-phase extraction cleanup with primary secondary amine and octadecylsilane, and finally analyzed by GC-MS/MS operated in electron impact (EI) and positive chemical ionization (PCI), and GC-MS in negative chemical ionization (NCI), respectively. An isotope internal standard, DDT-D8, was used for quantification. These three GC-MS procedures were validated and compared using crayfish samples fortified at three levels (5, 10 and 20 ng/g). Good linearity, accuracy, precision and sensitivity were achieved by all three ionization modes with recoveries in the range of 70 to 112 %, relative standard deviations (RSDs) below 10 % and limits of detection (LODs) in the range of 0.002 to 8 ng/g. Extremely high selectivity was obtained by both EI- and PCI-MS/MS, while PCI was more sensitive to compounds containing nitro and carbonyl groups, and EI was a better choice for dieldrin, endosulfan, and its metabolites. NCI-MS had the highest sensitivity but lower anti-interference ability and was not suitable for the determination of DDTs and PCBs. These three ionization modes can be used as complementary and alternative in routine GC-MS analysis of organochlorine pesticides and polychlorinated biphenyls in food. © 2012 Springer Science+Business Media, LLC. Source

Xia G.-H.,China Pharmaceutical University | Shen W.-J.,Jiangsu Entry Exit Inspection and Quarantine Bureau of PRC | Wu B.,Jiangsu Entry Exit Inspection and Quarantine Bureau of PRC | Lu H.-Y.,Jiangsu Entry Exit Inspection and Quarantine Bureau of PRC | And 8 more authors.
Chromatographia | Year: 2014

A modified quick, easy, cheap, effective, rugged, and safe sample preparation method combined with gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI/MS) has been developed for the determination of 7 dinitroaniline herbicide residues in complex matrices (garlic, olive oil, scallion, leek and chili). Dinitroaniline residues were extracted with hexane-saturated acetonitrile. After the cleanup with the dispersive solid-phase extraction, the extract was analyzed by GC-NCI/MS in selected ion monitoring mode. Two isotope internal standards (trifluralin-d 14 and pendimethalin-d 5) were employed for quantification. Compared with electron ionization (EI) mode, the superiorities of NCI in sensitivity and selectivity were investigated. Limits of the detection of 7 dinitroanilines were in the range of 0.014-0.096 μg kg-1, and there were no interfering peaks (unlike in EI) in the complex matrices. Recoveries of 7 dinitroanilines in five matrices at three spiked levels (10, 20 and 40 μg kg-1) ranged from 61 to 126 % and the relative standard deviations were all below 12 %. © 2014 Springer-Verlag. Source

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