Determination of polychlorinated biphenyls in biota samples using simultaneous pressurized liquid extraction and purification

In order to reduce time and cost of analysis, a new pressurised liquid extraction method that automatically and rapidly achieves quantitative and selective (i.e., lipid-free) extraction of polychlorinated biphenyls (PCBs) in biota tissues was optimized. It consists of on-line clean-up by inclusion of sorbents in the extraction cell. The freeze–dried sample is dispersed with Florisil and loaded in the extraction cell containing an extra amount of Florisil. The extraction is performed under mild conditions using 55 ml of a dichloromethane–pentane (15:85) mixture, a temperature of 40 °C, a static extraction time of 10 min and two extraction cycles. The Florisil retains coextracted lipids from the matrix, and the extract, after pre-concentration, is clean enough for direct injection into GC–MS and GC–electron-capture detection (ECD). Quantitative recoveries (from 90 to 106%) are obtained for both native and spiked PCB congeners in samples with a high lipidic content (up to 42% dry mass, in spoonbill eggs). The reproducibility of replicate extractions was better than 11% relative standard deviation. Method detection limits were in the ranges of 0.001–0.004 and 0.002–0.07 ng g−1 dry mass for GC–ECD and GC–MS–MS, respectively. The method was validated using the standard reference material SRM 2974 (a mussel tissue) from the US National Institute of Standards and Technology, compared to Soxhlet and matrix solid-phase dispersion extraction methods, and used to evaluate the contamination by PCBs in bivalves from South of Spain.