dissipation of imidacloprid in greenhouse cucumbers at single and double dosages spraying

in this study, residues of imidacloprid (confidor) were measured in greenhouse cucumbers in mazandaran province, iran. confidor 200 sl was applied at the recommended rate (30.0 g ai ha-1) and its double (60.0 g ai ha-1). samples were collected at 1 h to 21 days after application and analyzed to determine the content and dissipation rate of imidacloprid. . analysis was carried out by the quechers method using hplc-uv. the average initial deposits of imidacloprid on the cucumber fruits were found to be 1.93 and 3.65 mg kg-1 at the single and double dosages, respectively. results showed that imidacloprid was rapidly dissipated in cucumbers following a first order reaction kinetics at both application rates. the amount of dissipation in 21 days was 94.48% and 99.18% for, respectively, the single and double dosages. residues of imidacloprid dissipated below the maximum residue limit (mrl) of 1 mg kg_1 in 3 days. half-life (t1/2) for degradation of imidacloprid in cucumber was observed to be 3.40 and 2.70 days at the single and double dosages, respectively. a waiting period of 3 days is suggested for safe consumption of cucumber. also, results showed that the dissipation was dependent on the initial application dose and followed a first order rate kinetics.