Micelle formation for improvement of continuous subcritical water extraction of polycyclic aromatic hydrocarbons in soil prior to high-performance liquid chromatography–fluorescence detection

A new method for the extraction–individual separation–determination of polycyclic aromatic hydrocarbons (PAHs) in soil is reported. The method is based on the integration of three steps: continuous subcritical extraction, solid-phase clean-up/preconcentration, and HPLC separation with post-column fluorimetric determination. Sodium dodecyl sulfate (SDS) was added to the water for favouring the extractability of the low-polarity analytes. Soil samples spiked with the target PAHs were subjected to static–dynamic extraction with SDS–water at 50 bar, 150°C, for 15 min of static extraction and 10 min dynamic extraction at a flow-rate of 3 ml/min. Recoveries from 73.6 to 110.4% were obtained in the presence of SDS versus 30 to 80% obtained with water as extractant. The calibration graphs provided by HPLC–fluorimetric detection were run between 0.031 and 0.375 μg/ml for each analyte with regression coefficients between 0.917 and 0.999 and precision, expressed as RSD, between 1.2 and 11.5%. The method was applied to a certified reference material [CRM 524, BCR (Community Bureau of Reference), industrial soil/organic] for validation and the results obtained were in agreement with the certified values.