The wide use of pesticides in agriculture is necessary to guarantee adequate food production worldwide. However, pesticide residues have caused global concern because of their potential health risk to consumers. In this study, we could identify β-cypermethrin (β-CY) and its degradation product 3-phenoxybenzoic acid (3-PBA) by liquid chromatograph-mass spectrometry. Few studies on the simultaneous determination of β-CY and its metabolites have been carried out so far; hence, we established a high-performance liquid chromatography method to determine the concentrations of both β-CY and 3-PBA simultaneously in microbial degradation systems. In this study, a novel β-CY degrading strain, Bacillus licheniformis B-1, was isolated from a tea garden soil, utilizing β-CY as a growth substrate. Good linear relationships between β-CY and 3-PBA were observed and the concentrations of reference solutions were between 0.50 and 60.00 µg/mL. Satisfactory stability and intra- and interday precision were obtained. The limits of detection were 0.06 and 0.13 µg/mL for β-CY and 3-PBA, respectively, and the corresponding limits of quantification were 0.21 and 0.34 µg/mL, respectively. Spiking recoveries for β-CY varied from 98.38 to 105.80%, with relative standard deviations (RSDs) varying from 1.49 to 3.93%. Spiking recoveries for 3-PBA varied from 99.59 to 101.20%, with RSDs varying from 0.58 to 3.64%. The proposed method has advantages of simplicity, rapidity, high accuracy, good separation and reproducibility; thus, it is ideally suitable for simultaneous determination of β-CY and 3-PBA in microbial degradation systems.

The analytical method for the residue analysis of a novel herbicide, oxaziclomefone, and its dissipation in soil, water, rice plants and husked rice in rice fields at GAP (Good Agricultural Practices) conditions were studied. Oxaziclomefone residues were determined by GC-NPD. Mean recoveries ranged from 84.4 to 108.2% with relative standard deviations (RSDs) of 2.4 to 17.2% at three different spiking levels for each different matrix. The limits of quantification (LOQ) were found to be 0.01 mg/kg in soil, water, rice plants and husked rice and 0.02 mg/kg in rice hull. The mean half-lives of oxaziclomefone residues in water, soil and rice plants were 11.3, 37 and 4.4 days, respectively. At harvest, soil, straw, rice hull and husked rice samples were found to contain oxaziclomefone below the maximum residue level (0.1 mg/kg) set by Japan and Korea. Following the recommended application method, this herbicide is therefore safe to apply to rice fields.

The dissipation of ethofenprox in cabbage and soil under open conditions was investigated at two primary cabbage-growing regions, Beijing and Kunming in China. Samples were extracted with acetonitrile and determined by ultra-performance liquid chromatography with a single quadrupole detector. Dissipation of ethofenprox from cabbage and soil can be best explained by a first-order decay process. The half-lives of ethofenprox were 1.9 and 2.3 days in cabbage and 20.0 and 13.0 days in soil at Beijing and Kunming, respectively. The concentration of ethofenprox residue was reduced by 90% taking 7 and 60 days in cabbage and soil. Dissipation rates in cabbage and soil at two geographically separated experimental fields differed, suggesting that this was affected by complicated factors, such as local climate and soil characteristics. These data could provide guidance for the proper and safe use of this pesticide on cabbage in China.

A sensitive and effective analytical method for the determination of hymexazol in cucumber and soil samples by gas chromatography with a flame photometric detector was developed. This method was validated with fortified at three different levels of 0.2, 1.0 and 5.0 mg/kg. Average recoveries obtained from cucumber and soil samples at three fortified levels were 94.0%-107.8% with relative standard deviations (RSDs) of less than 11.4%. Limits of quantification (LOQ) in cucumber and soil were 0.2 mg/kg. The method was successfully applied to determine hymexazol in real samples of cucumber and soil under open fields.

Mefenoxam is the systemic phenylamide fungicide, which is widely used in controlling phytophthora disease of tomato, cucumber, pepper and watermelon, etc. The dissipation behaviour of mefenoxam residues in watermelons and soils was studied. The whole watermelon, melon flesh and soil matrices of mefenoxam were analyzed by GC-NPD. At three different spiking levels mean recoveries and relative standard deviation from spiked samples in six replicated experiments for each matrix were in the range 89.6-98.2% and 1.5-8.1%, respectively. Under field conditions, mefenoxam dissipation rate was found to be faster in the whole watermelons than in the soils. The results showed that the half lives in whole watermelon and soil from Beijing were 3.9 and 10.0 days, respectively, and the half lives in whole watermelon and soil from Shanxi were 3.7 and 28.4 days.