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Cao Z.,China National Rice Research Institute | Cao Z.,Laboratory of Quality and Safety Risk Assessment for Rice | Ma Y.,Zhejiang University | Mou R.,China National Rice Research Institute | And 5 more authors.
Chinese Journal of Chromatography (Se Pu) | Year: 2015

A method was developed for the determination of 17 cytokinins in rice by solid phase extraction and liquid chromatography-tandem mass spectrometry. The rice samples were cryogenically ground under liquid nitrogen and extracted with methanol-water (80:20, v/v) at 4 °C for 16 h. The supernatant was purified on a column packed with polymer cation exchange resin (PCX). The samples were transported and eluted on an analytical column ZORBAX Extend-C18 (100 mm×2.1 mm, 1.8 μm) by methanol and 5 mmol/L ammonium formate aqueous solution. All the analytes were detected in selected reaction monitoring (SRM) mode under positive electrospray ionization (ESI+) and quantified by external standard method. The separation conditions were optimized in order to achieve the sufficient separation for the several isomers of cytokinins, such as trans-zeatin-7-glucoside (tZ7G), trans-zeatin-9-glucoside (tZ9G), and trans-zeatin-O-glucoside (tZOG). Moreover, the extraction efficiency of different extraction solvents and clean-up effects of PCX cartridge for each analyte were further investigated. The results showed that the correlation coefficients were not less than 0.9984 in the linear range, and the limits of detection were ranged from 0.01 to 0.05 ng/g. The mean recoveries of the 17 cytokinins at three spiked levels of 0.2, 1 and 5 ng/g were from 60.2% to 125.4% with the relative standard deviations (RSDs) of 5.4%-29.7% (n=6). Finally, five endogenous cytokinins were successfully quantified in real sample, and their contents were between 0.02 and 0.93 ng/g. It means that this method is reliable for quantitative analysis of cytokinins in rice. Source


Cao Z.,China National Rice Research Institute | Cao Z.,Laboratory of Quality and Safety Risk Assessment for Rice | Mou R.,China National Rice Research Institute | Mou R.,Laboratory of Quality and Safety Risk Assessment for Rice | And 8 more authors.
Chinese Journal of Chromatography (Se Pu) | Year: 2014

An analytical method was developed for the simultaneous determination of 32 pesticides including organophosphorus, organochlorine, pyrethroid and carbamate pesticides in fruits and vegetables using gas chromatography-mass spectrometry (GC-MS). The sample was extracted with acetonitrile, and the organic layer was cleaned up with ENVI-Carb and LC-NH2 cartridges. A large volume of 20 μL purified solution was injected into the GC system using programmable temperature vaporizer (PTV). The mass spectrometry detection was operated with full scan mode. The automated mass spectral deconvolution and identfication system (AMDIS) and an isotopic internal standard were used for the qualitative and quantitative determination of the 32 pesticides, respectively. The conditions for PTV-large volume injection were studied. Furthermore, the selectivity and durability of the method were also assessed. Under the optimized conditions, the experimental results showed that all the linearities were good within their test ranges, with correlation coefficients more than 0.995, and the method detection limits of the pesticides were 2. 0-5. 0 μg/kg. The spiked recoveries (n=6) at three levels in the 0. 010-0. 50 mg/kg using spinach, snap bean and cucumber samples as blank matrices were in the range of 65. 2% -120. 3% with the relative standard deviations (RSDs) varying from 4. 1% to 22. 3o/o, showing good accuracy of the method. The advantages of the proposed method include high throughput, high sensitivity, reliability, robustness, and the ability to meet the demand of multi-residue pesticide analysis in fruits and vegetables. Source

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