The purpose of this investigation is to develop a simple method for the assessment of pesticides in Khat leaves,
Catha edulis
Forsk. (Celastraceae) shrub, chewed by about 60 % of the Yemeni people, producing amphetamine-like psychostimulation. The first procedures involve solid-phase extraction using Adsorbex® RP-C18 and Bakerbond® RP-C18 disposable cartridges with 40 % acetonitrile for elution. Isocratic and gradient analysis was carried out by means of high-performance liquid chromatography using different stationary phases to analyse methidathion, peconazole and dimethoate. An Ultrasphere®ODS RP-18-column with UV-detection at 210 nm and 80/20 % (v/v) acetonitrile/water as mobile phase (isocratic) was used to determine the content of methidathion, peconazole and dimethoate (detection limit 20-25 ng). The method was validated with fortified samples at pesticide concentration of 0.1 mg/ml. Average recoveries ranging from 97.9 and 101.6% with a relative standard deviation (RSD) of 1.7-3.8 %. Each recovery analysis was repeated four times. Limits of detection ranged from the analytical procedures were applied to 5 samples of khat and no detectable amounts of pesticides were found in any sample under the conditions described.
