Solid-phase extraction for replacing dichloromethane partitioning in pesticide multiresidue analysis

The Deutsche Forschungsgemeinschaft S 19 method is widely used for pesticide multiresidue analysis in crops. It includes a liquid-liquid partition step with dichloromethane, which is undesirable for toxicological and ecological reasons. Therefore, this step was replaced by a solid-phase extraction (SPE) of the diluted acetone extract with a mixture of RP-18-Polar-Plus and cyano material, which was afterwards eluted with ethyl acetate. Using this novel approach for extraction, concentration and clean-up, the recovery rates from fruits and vegetables fortified with 0.12-0.48 mg/kg of 31 pesticides with different chemical structures and polarities averaged 80% in most cases, except for some extremely polar compounds. The variation coefficients observed were near 5%, Compared to the partitioning step used hitherto, even higher recoveries were obtained by SPE for non-polar and medium-polar pesticides. In addition, the gas chromatograms often showed fewer interfering peaks from plant coextractives.