Determination of dithiocarbamate pesticide residues in tea by gas chromatography-tandem mass spectrometry

A method based on gas chromatography-tandem mass spectrometry (GC-MS/MS) was developed for the determination of dithiocarbamates pesticides (DTCs) in tea. Firstly, DTC pesticides were reacted with stannous chloride-hydrochloric acid solution in a closed headspace bottle in a water bath. The released carbon disulfide CS₂ was extracted by n-heptane and was detected and analyzed in multiple reaction monitoring (MRM) mode with GC-MS/MS. The results showed that the linear relationship (R²≥0.999) of CS₂ was good in the mass concentration ranges of 1-1000 μg/L. The method detection limit and quantification limit were 0.002 mg/kg and 0.005 mg/kg, respectively. The fortified recoveries were 81%-94% at three CS₂ equivalent levels of 0.005, 0.05, and 0.5 mg/kg, with the relative standard deviation of 3.7%-5.2%, and the detection repeatability was good. The established method was applied to 30 batches of tea samples, and it was found that the detection rate of DTCs was 10.0%, and the maximum detection value was 0.32 mg/kg. The method has the advantages of high sensitivity, simple operation and good selectivity, and is suitable for the detection and analysis of dithiocarbamate pesticides in tea.