Method Validation and Dissipation Behaviour of Dimethyl Disulphide (DMDS) in Cucumber and Soil by Gas Chromatography-Tandem Mass Spectrometry.

In this study, a useful analytical method was developed and validated for measuring the residues of dimethyl disulphide (DMDS) in cucumbers and soil by gas chromatography-tandem mass spectrometry (GC-MS/MS). The dissipation dynamics and residual levels of DMDS in cucumber and soil were also studied in Shandong, Jilin, and Hebei provinces by using this method. Dichloromethane was selected and used as the extraction solvent to extract the target pesticide from the soil and cucumber samples. The soil and cucumber samples were cleaned up by the combination of multiwalled carbon nanotubes (MWCNT) and biochar. The average recoveries of the DMDS in cucumbers and soil were in the range of 84-101.5%, with relative standard deviations (RSD) of 0.7-4.9%, when they spiked at 0.05, 0.5, and 5 mg/kg DMDS respectively. The limit of quantification (LOQ) of this method was 0.05 mg/kg. First-order and second-order kinetic equations were used to fit dissipation data. Results show that the half-lives of DMDS in the soil at Shandong, Jilin, and Hebei were 1.63-4.47 days, 1.96-6.49 days, and 1.35-2.51 days, respectively. The final residues of DMDS were less than 0.05 mg/kg in cucumbers and 0.36 mg/kg in the soil. The dissipation rates of DMDS in different soils were different. The method provides a basis for the risk assessment of DMDS in cucumber and soil.