High extraction efficiency for POPs in real contaminated soil samples using accelerated solvent extraction

Systematic investigations were performed to study the dependence of the ext raction efficiency of persistent organic pollutants (POPs), including chlor obenzenes, HCH isomers, DDX, PCB congeners, and PAHs, on the accelerated so lvent extraction (ASE) operating variables solvent and temperature. Mixed s oil samples from two locations with considerable differences in soil proper ties and contamination in the Leipzig-Halle region (Germany) were used. The objective was to optimize ASE for the extraction of POPs from real soil sa mples and to improve on the results achieved with Soxhlet extraction (SOX). Solvents with differing polarities were tested. Quadruple and triple deter minations were performed on the two soils, respectively, between 20 and 180 degrees C in 20 degrees C steps. All the results were compared with those obtained by SOX, as well as, in some cases during preliminary studies, by u ltrasonic extraction (USE). In ASE, the optimum conditions proved to be two extraction steps at 80 and 140 degrees C (average RSD 10.7%) with three st atic cycles (extraction time 35 min) using toluene as solvent and at a pres sure of 15 MPa. Owing to the superior analyte/matrix separation by ASE, in many cases for real soil samples analytical values better by up to 1 order of magnitude or even more were obtained compared to SOX results.