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 (C
t = 0.2627 e
-0.17t, C
t = 3.7183
e
-0.275t, C
t = 0.1778 e
-0.407t, C
t = 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).
