Persistence and Metabolism of Imidacloprid After Seed Treatment in Cotton Field Soil

A field study was carried out to determine the persistence and metabolism of imidacloprid in soil following its seed treatment @ 3.5 g and 14 g a.i. kg⁻¹ of seed. Soil samples were collected at different time intervals from 7–90 days after application and the residues of imidacloprid and its metabolites (6-chloronicotinic acid, imidacloprid-nitrogunidine, olefin, nitrosimine, urea and 5-hydroxy) were quantified by high-performance liquid chromatography. The total imidacloprid residues in soil were mainly constituted by the parent compound followed by olefin and nitrosimine. The limit of quantification for the analysis of imidacloprid and its metabolites was worked out to be 0.01 mg kg⁻¹. The maximum residues of total imidacloprid in soil samples collected 7 days after seed treatment were found to be 1.59 and 3.39 mg kg⁻¹for the two dosages, rspectively. These residues could not be detected after 60 days for both the dosages. Nitrosamine metabolite was found to be the maximum followed by olefin. The half-life values (t _1/2) of total imidacloprid were calculated to be 23.89 and 26.65 days, respectively, when applied at recommended dose and four times the recommended dose, respectively.