Simultaneous determination of cypermethrin and fenvalerate residues in tomato by gas chromatography and their applications to kinetic studies after field treatment

In this study simultaneous determination of cypermethrin and fenvalerate residues in tomato fruit (Lycopesicon esculentum) grown in Khartoum, Sudan, was carried out using gas chromatography with electron capture detector (GC-ECD). The method was linear in the ranges of 0.075-0.009 and 0.75-0.037 mg/mL for cypermethrin and fenvalerate, respectively. The limits of detection and quantification were found to be 0.003 and 0.01 mg/mL and 0.014, 0. 047 mg/mL for cypermethrin and fenvalerate, respectively. The recoveries of cypermethrin and fenvalerate spiked in tomato were 97 ± 7.5 and 99.5 ± 1.8%, respectively. The kinetic study of the degradation of both pesticides was performed and the ultimate evaluation of the kinetic data revealed a first-order kinetics with respect to the tomato fruit; an explanation was put forward to account for the results.