Gas Chromatographic Determination of Pesticide Residues in Plant Material after Clean-up by Gel Chromatography and Mini-silica Gel Column Chromatography. 1st Report: Organochlorine Pesticides in Tobacco and Tobacco Products/Gaschromatographische Bestimmung von Rückständen an Pflanzenbehandlungsmitteln nach Clean-up über Gelchromatographie und Mini-Kieselgel-Säulenchromatographie. 1. Mitteilung: Organochlor-Pflanzenbehandlungsmittel in Tabak und Tabakerzeugnissen

This report contains the first description of a method for pesticide residue determination using automated gel permeation chromatographic clean-up. The example of organochlorine pesticides in tobacco and tobacco products has been taken here to illustrate this method. Water is added to the sample which is then extracted with acetone such that the ratio of the volume of acetone used to the total volume of water is 2 :1. The key step in the method is the efficient removal of co-extracted plant constituents, by gel permeation chromatography on a polystyrene gel (Bio-Beads S-X3). The pesticides are recovered, without loss, in 65 ml of eluate. This eluate is further purified by very simple chromatography on a 1 g column of deactivated silica gel, two 10 ml fractions being collected. No interfering substances are present m these fractions and the pesticides may be identified and quantified without ambiguity. The limit of detection was, for example, for α-BHC 0.002 mg/kg and for p,p'-DDT 0.02 mg/kg. The recoveries of pesticides from spiked samples lay between 90 and 100 %. The method is also suitable for the extraction and purification of polar pesticides so that with a single sample processing a large number of different pesticides may be determined by GLC. This will be described in a forthcoming paper.