Residuesanddissipationofclothianidininpears

Residues and dissipation of clothianidin (20% SC) in pears were investigated in three locations through a two-year field experiment. Clothianidin in pears was determined by utra high performance liquid chromatography with photo-diode array detector. The samples were extracted by acetonitrile, cleaned up by the NH₂ column, and quantified by external standard method. At the fortified level of 0.05 to 2.5 mg/kg, the recoveries of clothianidin ranged from 95% to 103% with the relative standard deviations of 2.0% to 3.3%. The limit of quantification (LOQ) of this method was 0.05 mg/kg. The half-lives of clothianidin in pears were 12.0 d to 16.4 d. When the recommended dosage (a.i, 0.06 g/L) and 1.5 times of the recommended dosage (a.i, 0.09 g/L) of clothianidin (20% SC) were sprayed for 2-3 times, the terminal residues of clothianidin ranged from <0.05 mg/kg to 0.13 mg/kg 21 days after the last application. The final residues of clothianidin in pears were lower than the MRL of CAC (0.4 mg/kg).