Degradation Dynamics of Imidacloprid in Hainan Cowpea and the Soil
The HPLC method for imidacloprid in soil and cowpea was developed. The degradation dynamics of the imidacloprid in the soil and cowpea and the terminal residue in the cowpea were studied. The method recovery ranged 78% to 89% and the linear relationship was good from 0.05 to 5 μg/mL with a relative standard deviation less than 7%. The method limit of quantification was 0.01 μg/mL. The method could cover the detection requirement.The half-life of the imidacloprid in the soil and cowpea was 2.8 d and 3.7 d, respectively. The residue of the imidacloprid in the cowpea was less than 0.5 μg/g 2.5 days later when 1.5 times of the recommended dose of imidacloprid was sprayed. The half-life of the imidacloprid was short, which belongs to the easy degradation pesticide. The cowpea was sprayed once per 2 days for three times, respectively with 1.5 times and 2 times of the recommended dose. The results showed that the imidacloprid residue in the cowpea were less than 0.5 μg/g,respectively 4 days and 6 days later.