Residue and decline dynamics of nitenpyram in rice and rice field

The residual dynamics and final residues of nitenpyram in water,soil,paddy and rice samples in supervised field residue trials were determined by high performance liquid chromatography equipped with ultraviolet detector (HPLC-UVD).Water samples were extracted with methylene chloride.Soil samples were extracted with water only,and paddy and rice samples firstly with water then with acetone.The extracts were cleaned up by liquid-liquid extraction,and further cleaned up by column chromatography.Under the fortified level 0.1 to 5 mg/L for water,0.1 to 5 mg/kg for soil,and 0.2 to 5 mg/kg for paddy and rice,the recovery ranged from 77.2% to 100.3% with the relative standard deviations of 1.9%-12.9%.The limit of quantification (LOQ) of the method was 0.1 mg/L for water,0.1 mg/kg for soil,0.2 mg/kg for paddy and rice.The limit of detection (LOD) of the method was 0.04 mg/L for water,0.04 mg/kg for soil,0.08 mg/kg for paddy and rice.The results of simulating dynamic test in greenhouse showed that applied at exaggerated rate of dosage (1 500 g a.i./hm2), the half-life of nitenpyram was 0.58 days in water,3.31 days in soil and 2.70 days in paddy,respectively.When sprayed for 3 and 4 times at 1.5 times of the recommended dosage (112.5 g a.i./hm2),at interval time of 7 d after the last application,the final residues of nitenpyram in rice were lower than LOD (0.08 mg/kg) or the MRL of Japan (0.5 mg/kg).