Journal of Chromatography A, 774 (1997) 243–251 Evaluation of supercritical fluid extraction, microwave-assisted extraction and sonication in the determination of some phenolic compounds from various soil matrices a a a, b * ´ Marıa P. Llompart , Rosa A. Lorenzo , Rafael Cela , Ken Li , Jacqueline b b ´ ´ M.R. Belanger , J.R. Jocelyn Pare a ´ ´ ´ ´ ´ Departamento de Quımica Analıtica, Nutricion y Bromatologıa, Facultad de Quımica, Universidad de Santiago de Compostela, E-15706 Santiago de Compostela, Spain b Environment Canada, Microwave- Assisted Processes Division, Environmental Technology Centre, Ottawa, Ontario K1A 0H3, Canada Abstract Extraction methods using supercritical fluid extraction (SFE) and microwave-assisted process (MAP) techniques, with or without a one-step in situ derivatisation, were evaluated for the extraction of phenol, o-cresol, 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 analyte–matrix interaction. We also applied the methods to a real phenol contaminated 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 concentration steps. The results showed that SFE and MAP are more efficient 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 specific soils, SFE showed very low recoveries for the four phenols. However, recoveries were significantly improved when a derivatisation step was combined to SFE. In the real soil tested, the recoveries using derivatisation–extraction process were lower than the recoveries using extraction process. In general, derivatisation– extractions perform better and do not require extreme extraction conditions. Keywords: Extraction methods; Soil; Derivatisation, GC; Phenols; Cresols 1. Introduction tion carefully in the environment, specially for soil reclamation. Phenol and cresols are constituents of crude oil It has been recognized that the automatization of and coal tar. Also, phenol compounds are widely the measurement and determination stages in the used in the chemical industry. It is well known that analytical process has been developed significantly these compounds exhibit properties that are hazard- over the past decades. On the contrary sample ous to human health [1,2], thus making it necessary preparation automatization is comparatively much to identify the occurrence and levels of contamina- less developed. Much work has been carried out in the analysis of liquid samples [3]. However, solid or particulate samples represent a very important frac- * Corresponding author. tion in environmental studies. For these kind of 0021-9673 / 97 / $17.00 Copyright  1997 Elsevier Science B.V. All rights reserved PII S0021-9673(96)01025-4