Residual dynamics of emamectin benzoate in Chinese cabbage and cabbage.

A method for the determination of emamectin benzoate residues was developed,and residual dynamics of emamectin benzoate in Chinese cabbage and kohlrabi were studied.Residues of emamectin benzoate in Chinese cabbage,kohlrabi and soil were extracted by acetonitrile and cleanup with graphitic carbon,and determined by LC-MS.In this method,the lowest detectable amount was 0.5 ng,and the lowest concentration was 0.01 mg/kg.The recoveries of emamectin benzoate were 71.4%-93.2%,and RSD were 1.58%-8.98% when adding 0.01 mg/kg、0.05 mg/kg、0.50 mg/kg standard preparation.The results showed that in Chinese cabbage and soil trial,the half-lives of 1% emamectin benzoate were 1.3 d and 2.0 d respectively,and the half-lives of 5% emamectin benzoate in kohlrabi and soil were 1.0 d and 1.2 d respectively.Residue of emamectin benzoate in the Chinese cabbage and kohlrabi samples was lower than the MRL when adding 337.5 g/hm2 of 1% emamectin and 162.0 g/hm2 of 5% emamectin.