Headspace solid phase microextraction (HSSPME) for the determination of volatile and semivolatile pollutants in soils

We have investigated the use of headspace solid phase microextraction (HSSP ME) as a sample concentration and preparation technique for the analysis of volatile and semivolatile pollutants in soil samples. Soil samples were su spended in solvent and the SPME fibre suspended in the headspace above the slurry. Finally, the fibre was desorbed in the Gas Chromatograph (GC) injec tion port and the analysis of the samples was carried out. Since the transf er of contaminants from the soil to the SPME fibre involves four separate p hases (soil-solvent-headspace and fibre coating), parameters affecting the distribution of the analytes were investigated. Using a well-aged artificia lly spiked garden soil, different solvents (both organic and aqueous) were used to enhance the release of the contaminants from the solid matrix to th e headspace. It was found that simple addition of water is adequate for the purpose of analysing the target volatile organic chemicals (VOCs) in soil. The addition of 1 ml of water to 1 g of soil yielded maximum response. Wit hout water addition, the target VOCs were almost not released from the matr ix and a poor response was observed. The effect of headspace volume on resp onse as well as the addition of salt were also investigated. Comparison stu dies between conventional static headspace (IIS) at high temperature (95 de grees C) and the new technology HSSPME at room temperature ( similar to 20 degrees C) were performed. The results obtained with both techniques were i n good agreement. HSSPME precision and linearity were found to be better th an automated headspace method and HSSPME also produced a significant enhanc ement in response. The detection and quantification limits for the target V OCs in soils were in the sub-ng g(-1) level. Finally, we tried to extend th e applicability of the method to the analysis of semivolatiles. For these s tudies, two natural soils contaminated with diesel fuel and wood preservati ve, as well as a standard urban dust contaminated with polyaromatic hydroca rbons (PAHs) were tested. Discrimination in the response for the heaviest c ompounds studied was clearly observed, due to the poor partition in the hea dspace and to the slow kinetics of all the processes involved in HSSPME. (C ) 1999 Elsevier Science B.V. All rights reserved.