Effect of moisture on the extraction efficiency of polycyclic aromatic hydrocarbons from soils under atmospheric pressure by focused microwave-assisted extraction

The effects of the moisture content in the original, air-dried and re-moistened matrices as well as solvent have been studied on the recovery of polycyclic aromatic hydrocarbons (PAHs) from soil by a focused microwave-assisted extraction (FMAE) method. Solvents selected for the extractions were cyclohexane–acetone (1:1), hexane–acetone (1:1) and dichloromethane. On the extraction of 20-day aged spiked soil, the highest recovery was found by applying hexane–acetone mixture. Spiked soil sample, quality control sample and real soil sample were used for the evaluation of moisture effect. It indicated that the presence of water in the soil is important for the recovery enhancement of PAHs and with this presence it is possible to avoid drying step with the FMAE technique. A comparison between microwave and 16-h Soxhlet methods has been made. It evidenced that the microwave-assisted extraction under ambient atmospheric pressure is a suitable alternative to Soxhlet extraction for the analysis of PAHs in soils.