A high-performance liquid chromatography (Agilent 1100 HPLC
system, USA), with quaternary pump, thermostat compartment for
the column and photodiode array detector was used. Separation
was carried out on a carbon 18 (250 4.6 mm, 5 lm). The mobile
phase was acetonitrile: water (60/40 v/v) at a flow rate of
0.7 mL min1. Detection wavelength was set at 254 nm. The retention
time of thiamethoxam was about 4.05 min. Residues were
estimated by comparison of peak area of standards with that of
the unknown or spiked samples run under identical conditions.