Residue dissipation and risk assessment of tebuconazole, thiophanatemethyl and its metabolite in table grape by liquid chromatography-tandem mass spectrometry

An efficient method was developed and validated for simultaneous determination of tebuconazole, thiophanate-methyl and its metabolite carbendazim in grape and soil using QuEChERS procedure and liquid chromatography-tandem mass spectrometry. The average recoveries of the method were 83.2%-105.4%, the limit of detection (LOD) ranged from 2.1 x 10(-5) to 8.7 x 10(-4) mg L-1, and the limit of quantitation (LOQ) was 0.1 mg kg(-1). The field results showed that tebuconazole and thiophanate-methyl in soil and grape were rapidly dissipated with half-lives less than 24.7 days. The terminal residues of all analytes in grape were lower than the maximum residue limit (MRL) set by China (2 mg kg(-1) for tebuconazole; 3 mg kg(-1) for both thiophanate-methyl and carbendazim). Risk assessment showed that tebuconazole, thiophanate-methyl and its metabolite would be unlikely to cause health problems. However, carbendazim, the higher active metabolites of thiophanate-methyl, should receive more concerns.