Determination Of Fipronil And Its Metabolites In Tea And Tea Infusion And Study Of The Leaching Rate

Based on QuEChERS technique,a method for the simultaneous determination of fipronil and its metabolites in tea was developed by gas chromatography-tandem mass spectrometry.The samples were added with internal standard of fipronil-¹³C₂,¹⁵N₂,then extracted with acetonitrile from tea after water soaking.The extract was dehydrated with sodium chloride?NaCl?and anhydrous magnesium sulfate?MgSO₄?and purified by dispersive solid phase extraction?d-SPE?with N-propyl Ethylenediamine?PSA?and Graphite carbon?GCB?.The analytes were detected by tandem mass spectrometry with multiple reaction monitoring?MRM?mode,and the internal standard method was used for quantification.A good linearity in the range of0.4¹00?g/L with correlation coefficients?R²?>0.995 was observed.The limits of the quantification?LOQs?for fipronil and its metabolites were 1?g/kg.The recoveries of the fipronil and its metabolites at four spiked levels?1,5,20 and 200?g/kg?were in the range of 76.72%⁹6.53%with the relative standard deviations?RSD,n=6?between 4.76%¹3.07%.The method was simple,sensitive and accurate,and was suitable for the rapid quantitative analysis of fipronil and its metabolites in tea.The sensitivity of the method can meet the requirement for residual limitation of EU and Japan.At the same time,we based on two different ways to analyse tea infusion:Liquid-Liquid extraction?LLE?and solid phase extraction?SPE?,the methods for the simultaneous determination of fipronil and its metabolites in brewing tea was developed by gas chromatography-tandem mass spectrometry.In LLE,the samples were added with internal standard of fipronil-¹³C₂,¹⁵N₂,then extracted with dichloromethane from tea infusion after brewing.The extract was demulsificated with anhydrous magnesium sulfate?MgSO₄?,The analytes were detected by tandem mass spectrometry with multiple reaction monitoring?MRM?mode,and the internal standard method was used for quantification.A good linearity in the range of 0.4¹00.0?g/L with correlation coefficients?R²?>0.999 was observed.The limits of the quantification?LOQs?for fipronil and its metabolites were 0.02?g/L.The recoveries of the fipronil and its metabolites at three spiked levels?0.10,0.40 and 4.00?g/kg?were in the range of 71.72%⁹5.76%with the relative standard deviations?RSD,n=6?between 4.05%¹0.30%;In SPE,the samples were added with internal standard of fipronil-¹³C₂,¹⁵N₂,then concentrated and purificated with C₁₈ after prewashing by dichloromethane,methanol and water.The analytes were detected by tandem mass spectrometry with multiple reaction monitoring?MRM?mode,and the internal standard method was used for quantification.A good linearity in the range of0.08¹00.0?g/L with correlation coefficients?R²?>0.997 was observed.The limits of the quantification?LOQs?for fipronil and its metabolites were 0.48 ng/L.The recoveries of the fipronil and its metabolites at three spiked levels?0.02,0.80 and 8.00?g/L?were in the range of 95.25%¹19.75%with the relative standard deviations?RSD,n=6?between 3.24%⁶.34%.The method was simple,sensitive and accurate,and was suitable for the rapid quantitative analysis of fipronil and its metabolites in tea infusion.The leaching rate of fipronil and its metabolites during tea and tea infusion was studied by the above methods.The total leaching rate of fipronil and its metabolites were less than 52.4%,the residues of fipronil and its metabolites in the samples with the highest content were not higher than 31?g/kg around this leaching rate.Calculated the maximum intake of the human body is 0.00369?g/kg?d?bw,this is only 1.85%of the fipronil acceptable daily intake?ADI?value?0.0002mg/kg?d?bw?.That means at this concentration is theoretically safe for drinking.