Dissipation of four insecticides in tomato fruit using high performance liquid chromatography and QuEChERS methodology
Insecticides play an important role in increasing agricultural production, but their extensive use has led to environmental problems including health hazards to humans. The present study was carried out to investigate the residual levels and dissipation behavior of four insecticides, namely abamectin, thiamethoxam, spinosad, and chlorpyrifos, in tomato (Solanum lycopersicum L.) fruits under Egyptian field condition. The insecticide residues were determined after application of insecticides for three times at recommended rates. The extraction of insecticide residues was carried out by using QuEChERS method. The determination of residual levels was performed by high performance liquid chromatography coupled with diode array detector (HPLC-DAD). Recoveries were between 85% and 130%, with relative standard deviations from 1.8% to 17.0% at two fortified levels. The dissipation rates of insecticides followed first-order kinetics (Ct = 0.2627 e-0.17t, Ct = 3.7183 e-0.275t, Ct = 0.1778 e-0.407t, Ct = 0.6074 e-0.11t for abamectin, chlorpyrifos, spinosad and thiamethoxam, respectively). The values of half-life of insecticides were 4.1, 2.5, 1.7, and 6.3 d for abamectin, chlorpyrifos, spinosad and thiamethoxam, respectively. The results indicated that tomato fruits could be safely consumed after 7, 15, < 1 and 10 d of application at recommended rates for abamectin, chlorpyrifos, spinosad and thiamethoxam, respectively, according to the recommended EU maximum residue limits (MRLs).