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Yao Z.,Zhejiang Academy of Agricultural Sciences | Yao Z.,MOA Key Laboratory for Pesticide Residue Detection | Yao Z.,Zhejiang University of Technology | Lin M.,Zhejiang Academy of Agricultural Sciences | And 9 more authors.
Journal of Separation Science | Year: 2015

An efficient enantioselective method for the simultaneous determination of isocarbophos and its main metabolite isocarbophos oxon in rice, soil, and water was developed using liquid chromatography with tandem mass spectrometry. The enantioseparation was performed on a Chiralpak AD-3R column at 30°C using gradient elution. Target compounds were extracted from soil and rice using acetonitrile with omission of a clean-up procedure, while a C18 solid-phase extraction column was used for water samples. Quantification was achieved using matrix-matched calibration. The overall mean recoveries for isocarbophos and isocarbophos oxon enantiomers from the five matrices were 89.7-103 and 90.1-98.7%, with relative standard deviations of 2.1-5.4 and 2.5-4.7%, respectively. Moreover, the absolute configurations of isocarbophos oxon enantiomers were determined by liquid chromatography with tandem mass spectrometry through incubation of each isocarbophos enantiomer in soil, the first eluting enantiomer being confirmed as (R)-(-)-isocarbophos oxon. The proposed method was applied to real soil samples and satisfactory results were obtained. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Yao Z.,Zhejiang Academy of Agricultural Sciences | Yao Z.,MOA Key Laboratory for Pesticide Residue Detection | Yao Z.,Zhejiang University of Technology | Li X.,CAS Shanghai Institute of Organic Chemistry | And 8 more authors.
Analytical and Bioanalytical Chemistry | Year: 2015

A novel, sensitive, and efficient enantioselective method for the determination of triadimefon and its metabolite triadimenol in edible vegetable oil, was developed by gel permeation chromatography and ultraperformance convergence chromatography/tandem triple quadrupole mass spectrometry. After the vegetable oil samples were prepared using gel permeation chromatography, the eluent was collected, evaporated, and dried with nitrogen gas. The residue was redissolved by adding methanol up to a final volume of 1 mL. The analytes of six enantiomers were analyzed on Chiralpak IA-3 column (150 × 4.6 mm) using compressed liquid CO2-mixed 14 % co-solvents, comprising methanol/acetonitrile/isopropanol = 20/20/60 (v/v/v) in the mobile phase at 30 °C, and the total separation time was less than 4 min at a flow rate of 2 mL/min. Quantification was achieved using matrix-matched standard calibration curves. The overall mean recoveries for six enantiomers from vegetable oil were 90.1-97.3 %, with relative standard deviations of 0.8-5.4 % intra-day and 2.3-5.0 % inter-day at 0.5, 5, and 50 μg/kg levels. The limits of quantification were 0.5 μg/kg for all enantiomers based on five replicate extractions at the lowest fortified level in vegetable oil. Moreover, the absolute configuration of six enantiomers had been determined based on comparisons of the vibrational circular dichroism experimental spectra with the theoretical curve obtained by density functional theory calculations. Application of the proposed method to the 40 authentic vegetable oil samples from local markets suggests its potential use in enantioselective determination of triadimefon and triadimenol enantiomers. [Figure not available: see fulltext.] © 2015 Springer-Verlag Berlin Heidelberg. Source


Zhang H.,Nanjing Agricultural University | Zhang H.,Key Laboratory of Integrated Management of Crop Diseases and Pests | Zhang H.,State Key Laboratory Breeding Base for Zhejiang Sustainable Plant Pest Control | Zhang H.,MOA Key Laboratory for Pesticide Residue Detection | And 15 more authors.
Journal of Separation Science | Year: 2012

The enantiomeric separation of 21 triazole fungicides was carried out on four polysaccharide-derived chiral stationary phases in the reversed phase separation mode using high performance liquid chromatography coupled with tandem mass spectrometry. All fungicides were detected in electrospray ionization (ESI) positive mode with selected reaction monitoring (SRM). Complete enantioseparation was achieved for 21 fungicides except for difenoconazole based on cellulose tris (3,5-dimethylphenylcarbamate) and cellulose tris (3-chloro-4-methylphenyl carbamate) columns by optimizing experimental conditions including mobile phase and column temperature. Mobile phase was 0.1% formic acid aqueous solution mixed with methanol or acetonitrile in different proportions. Among all the fungicides, 15 with two enantiomers and three with four stereoisomers (bitertanol, bromuconazole, and cyproconazole) were successfully separated at 25°C. Enantioseparation for the other three fungicides (propiconazole, triadimenol, and difenoconazole) with four stereoisomers could be achieved by changing the column temperature from 10 to 40°C. Propiconazole and triadimenol were enantioseparated on baseline at 40 and at 35°C, respectively, and difenoconazole was enantioseparated partially with the Rs > 1.1 at 25°C. Moreover, linearities and limits of detection (LODs) of 21 fungicides except for difenoconazole were studied, showing coefficients of determination (R2) higher than 0.99 and LODs lower than 2.5 μg/L. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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