Residual characteristics and dietary exposure risk assessment of valifenalate and mancozeb
A trace analytical method for valifenalate,mancozeb and its metabolite ethylenethiourea(ETU)was established in grape and cucumber in this study.Based on the favorable storage stability,the fate characteristics of targeted compounds were clarified,and then highlighted their dietary exposure risks in combination with Chinese dietary structure.The samples were extracted with acetonitrile,then derivatized,salted out and centrifuged,and purified by dispersive solid-phase extraction(d-SPE),finally determined by ultra-high performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS).The mean recoveries of valifenalate,mancozeb and ETU in grape and cucumber matrices were 84％-103％,86％-106％and 83％-104％with relative standard deviations(RSD)of 1.1％-5.7％,0.8％-11.4％and 4.4％-11.5％.Target compounds could be stored stably for 720 d and 758 d at-20℃ in cucumbers and grapes under dark,respectively.The half-lives of valifenalate(1.7-2.4 d)and mancozeb(1.4-2.7 d)in cucumber were shorter than those in grape(6.5-30.1 d and 8.6-12.8 d).The residue levels of valifenalate and mancozeb in grape(＜0.01-0.69 mg/kg)were higher than those in cucumber(＜0.01-0.16 mg/kg).The acute dietary risks(％ARfD)of mancozeb in children and general population were 0.70％to 3.68％and 0.48％to 2.53％,respectively.The joint chronic dietary risks of mancozeb and valifenalate were 201.3％to 831.7％,of which mancozeb accounted for 99.9％.Therefore,valifenalate would not cause unacceptable exposure risk to consumers,however,the high potential exposure risk of mancozeb should be alerted and more attention should be paid to its bioaccumulation risk in the food chain.The dietary structure should also be optimized to provide a theoretical basis for the scientific application and risk avoidance of valifenalate and mancozeb.
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