Degradation of Fipronil and Its Metabolites during Processing of Yunnan Black Tea and Dietary Exposure Assessment

The purpose of this study was to investigate the residual degradation of fipronil and its metabolites during the processing of black tea and its dietary exposure risk. In this study,ultra-high performance liquid chromatography-tandem mass spectrometry and TPT SPE columns were used to establish a high-sensitivity and rapid determination method for fipronil and its metabolites in black tea. In the negative ion MRM monitoring mode,the linear range of fipronil and its metabolites was 0.5~100 μg/mL,the linear relationship was good,and the minimum detection limit was 0.4 μg/kg. The average recovery rate under different additive concentrations was 84.4%~95.5%,which met the requirements of trace detection. By spraying fipronil and its metabolites in the fresh leaves of the black tea,and simulating the processing of the indigo tea,and sampling and measuring the content of fipronil and its metabolites in the main steps of the processing of the indigo tea,the results showed that the content of fipronil and its metabolites was continuously reduced during the processing of Yunnan black tea,and fipronil and its metabolites were largely degraded in the two steps of rolling and drying,and the degradation rates of these two steps ranged from 37.5% to 41.2% and 65.1% to 70.1%,respectively. The results of HQ calculation showed that the dietary exposure risk of fipronil and its metabolites was low,while the total hazard index HI was greater than 1,and the dietary risk was unacceptable. At present,fipronil and its metabolites have been banned in tea. It is less likely to use four pesticides in sapling tea,but should be taken seriously.