SPME determination of low concentration levels of monoaromatic chemical markers in soils after remediation by supercritical fluid extraction

Soil contamination by organic compounds has been a serious concern over the years. Among the various forms of pollutant release, gas station contamination has been widely emphasized. The presence of simple aromatic compounds in soils sampled near gas stations may indicate contamination, considering that such compounds are frequently found in petroleum-derived products. The present paper reports on the development of a process that uses pressurized fluids for the remediation of contaminated soils. Supercritical fluid extraction (SFE) employing CO2 as the solvent and an 11.0 g capacity extraction cell was utilized. In order to demonstrate the efficiency of the process, an analytical procedure employing headspace-solid phase micro extraction (HS-SPME) as the sample preparation method and GC-MS as the separation technique was optimized and validated. Limits of quantification and detection obtained were in agreement with the values established by national and international regulatory agencies. The linear range obtained was from 10 to 260 mu g kg(-1), with determination coefficients r(2) > 0.98 for all analyses. Different removal rates were observed for the contaminants studied, the best results being achieved by employing CO2 in a supercritical state.