Microwave assisted solvent extraction (MASE) of organochlorine pesticides from soil samples

The use of Microwave Assisted Solvent Extraction (MASE) for the liquid-solid extraction of a group of organochlorine pesticides from soil samples was investigated. Analysis of the pesticides took place by gas chromatography with electron-capture detection. To optimize MASE, several extraction solvents and solvent mixtures were tested. Also the influence on the extraction of the amount of water added to the soil samples before MASE was studied. The developed procedure was applied to the extraction of a group of 16 organochlorine pesticides and metabolites from different soil types (clay, sand, peat and upper layer). The same samples were extracted by a conventional liquid extraction method. Comparing the obtained results indicated that MASE yields recoveries that are equal to or better than obtained by the conventional method, e.g 90-100% vs. 45-102% with RSDs in the range 2-6% vs. 4-22%, respectively. The developed MASE procedure also considerably reduces organic solvent consumption, extraction time and the amount of manual operation. The selectivity of MASE was highly dependent on soil composition. For samples with a high organic content, a simple SPE clean up procedure over silica is required before analysis. The sensitivity of the method is at the sub ppb level in soil for all the compounds analysed (ppb level for upper layer). The developed MASE procedure was applied to the analysis of 120 soil samples with possibly incurred residues.