Trace enrichment of polychlorinated biphenyls in soil: Efficiency of sonicated liquid-solid extraction with acetone/n-hexane mixture from different soil types

The efficiency and reproducibility of an analytical procedure for trace det ermination of polychlorinated biphenyls (PCBs) in soil/sediment samples wer e evaluated by analyses of soils differing in their sorption-controlling pr operties. PCBs were accumulated from soil by sonicated multiple extraction with a 1:1 acetone/n-hexane mixture. The extracts, purified by treatment wi th copper powder, mercury, and sulphuric acid were analyzed by gas chromato graphy. The extraction efficiency from a soil spiked with 4-430 mu g kg(-1) of Aroclor 1242/Aroclor 1260 mixture depended on the initial PCB mass frac tion. The matrix effect was evaluated by the analysis of PCBs added to five European reference soils differing in organic matter content, grain size d istribution, mineral composition, pH values, and iron and aluminium oxides content. In four of these soils, a linear correlation was found between the slopes of calibration lines for the determination of PCBs and soil organic matter content. An exception was the most acidic soil with the highest, bu t poorly humified, organic matter. The linear regression of calibration lin e slopes and the content of soil fine silt particles indicated a positive, but not statistically significant, correlation.