Toxicologie environnementale et analytique

Permethrin and Cypermethrin Residues on Beans and Cucumber Plants Grown Under Greenhouse Conditions

Abstract

George Antonious

A simple, accurate, and cost-effective procedure for separation and quantification of two pyrethroid insecticides residues on bean and cucumber plants was achieved using a Gas Chromatograph (GC) equipped with an electron capture detector (GC-ECD) and GC equipped with a Mass Selective Detector (MSD). Following spraying fruits and leaves were collected to determine insecticides dissipation constants and half-lives (T^1/2 values). Residues of the two pyrethroids revealed the presence of permethrin isomers at retention times of 26 and 26.6 min that correspond to the cis and trans-isomers, respectively. The GC also revealed the presence of four cypermethrin isomers at retention times of 30.3, 30.9, 31.3, and 31.5 min. The average initial deposits of permethrin were 2.7 and 0.2 on cucumber leaves and fruits surfaces, respectively. Whereas cypermethrin initial deposits were 5.1 and 2 μg g-1 on cucumber leaves and fruits, respectively indicating greater deposits on leaves than fruits. T^1/2 values of permethrin and cypermethrin residues on beans pods (7.2 and 9.5 d, respectively) and cucumber fruits (13 and 3.3 d, respectively) indicated that a waiting period of 10 and 15 d are required for consumption of cucumber fruits and bean pods sprayed with cypermethrin at the recommended spraying dosage to drop the residues to the Maximum Residue Limits.