Analysis, Detection, Residue Fate And Dietary Risk Of Tolfenpyrad In Four Leafy Vegetable

A novel and accurate analytical method was developed and applied on the investigation of dissipation dynamics and terminal residue of tolfenpyrad in Brassica bara L.(BBL),Spinacia oleracea L.(SOL),Lactuca sativa L.(LSL)and Brassica chinensis L.(BCL)samples under greenhouse conditions.Combined the field data with the dietary intake evaluation models,the safety and potential dietary intake risk of tolfenpyrad in BBL,SOL,LSL and BCL under greenhouse conditions were assessed for Chinese consumers.The leafy green vegetable samples were extracted with acetonitrile,salted out with anhydrous magnesium sulfate and sodium chloride.Then the organic phase was purified,concentrated and detected by gas chromatography with tandem mass spectrometry.The results showed that the established method had good linearity(R~2>0.999).The matrix effect(ME)values were-28 to-9 that a matrix inhibition effect was observed,so the matrix-standard curve based external standard method was used for quantification.The limits of detection(LODs)and quantitation(LOQs)were0.003 and 0.01 mg/kg,respectively.The average recoveries were from 79.2%to 92.9%and the relative standard deviations(RSDs)were<8%.The above data demonstrated that the accuracy and precision of the method met the requirements of pesticide residue analysis.In the greenhouse field trials,the formulation of tolfenpyrad(15%,suspension concentrate)was sprayed at two doses of 67.5 and 112.5 g a.i./ha and two spraying times of once and twice with an interval of 7 d.The sampling intervals were 0(2 h),1,2,3,5,7,10,14,21 and 28 d.The half-lives of tolfenpyrad in BBL,SOL,LSL and BCL were 4.0-6.8 d,5.3-6.6 d,3.5-4.5 d and 2.0-3.1 d,respectively,which indicated that tolfenpyrad dissipated fast in four vegetables.The terminal residual data showed that 21 d could be recommended as the pre-harvest interval(PHI)for BCL and 28 d could be recommended as the PHI for BBL,SOL and LSL under greenhouse conditions.Based on the dietary intake risk assessment data of tolfenpyrad in BBL,SOL,LSL and BCL,the chronic and acute risk quotients(RQ_cs and RQ_as)in BBL and SOL samples collected 14 d after the last application were less than 100%,indicating that the chronic and acute dietary intake risk of tolfenpyrad in BBL and SOL were safe for Chinese consumers.The RQ_cs and RQ_as in LSL and BCL samples collected 21 days after the last application were also less than 100%,which demonstrated that the residues of tolfenpyrad in LSL and BCL were safe for Chinese consumers.