EVALUATION OF SUPERCRITICAL-FLUID EXTRACTION, MICROWAVE-ASSISTED EXTRACTION AND SONICATION IN THE DETERMINATION OF SOME PHENOLIC-COMPOUNDS FROM VARIOUS SOIL MATRICES

Extraction methods using supercritical fluid extraction (SFE) and micr owave-assisted process (MAP) techniques, with or without a one-step in situ derivatisation, were evaluated for the extraction of phenol, o-c resol, m-cresol and p-cresol from soils. Five artificially spiked soil matrices were prepared; three of them were prepared by adding various amounts of activated charcoal in order to increase the degree of anal yte-matrix interaction. We also applied the methods to a real phenol c ontaminated soil with a high carbon content (18%). To provide a basis for comparison, all the soils were extracted using an US Environmental Protection Agency-approved sonication protocol. The extracts obtained were analyzed on a GC-MS system without any preliminary clean-up or c oncentration steps. The results showed that SFE and MAP are more effic ient than sonication with at least twice the recovery in all the soils tested. MAP and MAP-derivatisation showed the best recoveries (>80%) for the five spiked matrices studied with the exception of o-cresol in soils with activated charcoal content higher than 5%. In these specif ic soils, SFE showed very low recoveries for the four phenols. However , recoveries were significantly improved when a derivatisation step wa s combined to SFE. In the real soil tested, the recoveries using deriv atisation-extraction process were lower than the recoveries using extr action process. In general, derivatisation-extractions perform better and do not require extreme extraction conditions.