Determination of thiamethoxam and its metabolite clothianidin residue and dissipation in cowpea by QuEChERS combining with ultrahigh-performance liquid chromatography–tandem mass spectrometry
2021
Chen, Li | Li, Fugen | Jia, Chunhong | Yu, Pingzhong | Zhao, Ercheng | He, Min | Jing, Junjie
The dissipation and residue levels of thiamethoxam and its metabolite clothianidin in cowpea were investigated under field conditions. Samples of cowpea were analyzed using a QuEChERS technique with ultra-performance liquid chromatography tandem mass spectrometry. The recoveries were 86.5–118.9% for thiamethoxam and 75.6–104.1% for clothianidin, with the coefficient of variation of < 13%. The water dispersible granule formulation of thiamethoxam was applied on cowpea at 30 and 45 g active ingredient ha⁻¹ in accordance with good agricultural practice. The half-life of thiamethoxam in cowpea was 0.8–1.6 days. The cowpea samples were gathered at 3, 7, and 10 days after the last application, and the residues of thiamethoxam in cowpea were < 0.005–0.054 mg kg⁻¹, while those of clothianidin were < 0.005–0.008 mg kg⁻¹. The final residues of thiamethoxam and clothianidin were below the European Union (EU) maximum residue level (0.3 mg kg⁻¹ for thiamethoxam; 0.2 mg kg⁻¹ for clothianidin) in cowpea after a preharvest interval (PHI) of 7 days. This study provided basic data on the use and safety of thiamethoxam and clothianidin in cowpea to help the Chinese government formulate a maximum residue level for thiamethoxam in cowpea.
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