Automated fast extraction of nitrated polycyclic aromatic hydrocarbons from soil by focused microwave-assisted Soxhlet extraction prior to gas chromatography–electron-capture detection

An approach for the automated fast extraction of nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) from soil, using a focused microwave-assisted Soxhlet extractor, is proposed. The main factors affecting the extraction efficiency (namely: irradiation power, irradiation time, number of cycles and extractant volume) were optimised by using experimental design methodology. The reduction of the nitro-PAHs to amino-PAHs and the derivatisation of the reduced analytes with heptafluorobutyric anhydride was mandatory prior to the separation-determination step by gas chromatography–electron-capture detection. The proposed approach has allowed the extraction of these pollutants from spiked and “real” contaminated soils with extraction efficiencies similar to those provided by the US Environmental Protection Agency methods 3540-8091, but with a drastic reduction in both the extraction time and sample handling, and using less organic solvent, as 75–85% of it was recycled.