Residue and dissipation for different formulations of imidacloprid in tobacco leaf and soil

The field trial on tobacco leaf and soil on four formulations of imidacloprid,including soluble concentrate (SL),wettable powder (WP),micro-emulsion (ME) and granule (GR) were performed through orthogonality experiment considering different dosages,different application times and recovery intervals in year 2010-2011.The samples were analyzed by high-performance liquid chromatography (HPLC).Imidacloprid residue dissipation and final residues of different formulations of imidacloprid in tobacco leaf and soil were studied.The average recoveries at 3 different levels and 5 replicates were from 85.6% to 89.3%,85.0% to 88.3% and 84.1% to 91.5%,with relative standard deviations (RSDs) from 5.0% to 5.7%,3.5% to 5.0%,and 3.4% to 8.0% in fresh tobacco leaf,cured tobacco leaf and soil,respectively.The limit of detection (LOD) was 0.3 ng(S/N=3),and the limit of quantification(LOQ) was 0.01,0.01 and 0.03 mg/kg in fresh tobacco leaf,soil and cured tobacco leaf.The dissipation rates of four kinds formulation of imidacloprid were fast with half-lives of 5.7-6.6,3.1-3.7,5.0-5.1,10.5-11.4 d,respectively.The pesticide residues at different dosages,different frequencies and intervals in cured tobacco leaves varied in these situations.According to the GRL of CORESTA,14 days harvest intervals were recommended for three formulations sprayed at the growth phase and 70 days for granules which used into soil when transplanting.