Untargeted screening of pesticide residues in coix seed by LC-MS/MS and dietary risk assessment

Coix seed (C. lacryma-jobi L.) is used as a medicinal and edible grain in China. In this study, nontargeted screening of pesticide residues in 126 coix seed samples was conducted in Guizhou Province, southwestern China. The 39 pesticides screened were detected and quantified using a liquid chromatography-tandem mass spectrometry method after modified QuEChERS pretreatment. The samples were extracted with an acetonitrile-formic acid (98:2;v/v) mixture. Method linearity was confirmed between 0.001-1 mg kg-1, with significant correlation coefficients (R2 >0.980). Mean recoveries were 72.2%-115% and the limit of quantification was 0.01 mg kg-1. Intraday repeatability and inter-day reproducibility ranged from 0.2% to 17.8% and 0.3% to 18.0%, respectively. Risk assessment showed that Hazard Quotient (HQ) and Hazard Index (HI) were well below 1. This method can help to regulate pesticide use in cultivation areas and improve the quality and safety of coix seed products.