Sample handling in analysis of pesticide residues in foodstuffs

To get a good precision of data generated determination of pesticide residues in foodstuffs, an efficient clean-up of primary extracts has to be carried out. In our experiments, automated (ASPEC XL. Gilson, France) gel permeation chromatography was used for purification of ethyl acetate extracts of spinach, carrots and apples which were spiked by 42 pesticides (0.05-0.4 mg.kg(-1)) currently detected in respective crops. The advantages of rigid Pl gel over soft BioBeads SX-3 were demonstrated. In system consisting of a Pl gel column (10 mm, 600 x 0.75 mm) with ethyl acetate-cyclohexane (1:1, v/v) as a mobile phase, good efficiency and high repeatability of clean-up step were obtained, the recoveries of pesticides ranging from 70 to 105 %.