Residue and dissipation of clothianidin in tomatoes and soil

A two-year field experiment was conducted to study the residue and dissipation dynamics of clothianidin (50% WDG) in tomatoes and soil in three locations. The dispersive solid phase extraction (DSPE) combined with high performance liquid chromatography-tandem mass spectrometry (HPLCMS/MS) method was developed for the rapid determination of the clothianidin residue in tomatoes and soil. The results indicated that the recoveries at spiked level of 0.005, 0.01 and 0.05 mg/kg in tomatoes were in the range of 90%-121%, with relative standard deviation of 4.0%-4.5% (n=5); and the recoveries for soil samples were in the range of 88%-92%, with relative standard deviation of 3.6% -5.8% (n=5). The limits of quantitation (LOQ) for clothianidin in tomatoes and soil were both 0.005 mg/kg, which could meet the requirement of max residue limits (MRLs) of clothianidin. The dissipation dynamics of clothianidin in tomatoes fitted the pseudo-first-order kinetics equations, and the half-lives of clothianidin were estimated to be 3.5-17.3 d in tomatoes. If tomatoes were treated three times and interval of 7 days with the available dosage of 60 g/hm2 during the growing season, the final residue of clothianidin is