DIATOMACEOUS EARTH-ASSISTED EXTRACTION FOR THE MULTIRESIDUE DETERMINATION OF PESTICIDES

An effective multiresidue diatomaceous earth-assisted extraction and g as chromatographic-electron capture detection and thermionic sensitive detection of over 90 pesticides belonging to several chemical familie s is described. The homogeneous vegetal sample pulp was mixed with dia tomaceous earth to obtain a free-flowing powder which was extracted wi th ethyl acetate. Recoveries of several pesticides including apolar an d polar ones were tested in 10 replicates on apple material and the an alysis performed on two GLC systems, each one equipped with two column s of different polarities and two detectors. The recovery of pesticide residues belonging to different chemical classes on the matrix studie d was satisfactory (72-116%) for the pesticides studied and no further clean-up was required for subsequent gas chromatographic analysis. Re sults are discussed according to the combination column-detector used.