Supercritical fluid extraction of polychlorinated biphenyls from lyophilized fish tissue

A method for the rapid interference free analysis of polychlorinated biphenyl congeners (chlorinated biphenyls, CBs) in lyophilized fish tissue is presented. The method was developed on a lyophilized tuna muscle tissue that contained 2.8% lipid (dry mass based), and native CB concentrations in the range of 3-84 ng/g. Sample preparation was made by supercritical fluid extraction using pure CO2 as extraction fluid. Analysis by high-resolution gas chromatography-electron-capture detection analysis was carried out with on-column injection on two parallel coupled columns, a 60 m DB-17 column and a series combination of a 25 m SIL-8 column and a 25 m HT-5 column. Supercritical fluid extraction was compared with Soxhlet extraction and found to give quantitative recoveries, detection limits of 0.5-2 ng/g and standard deviations of less than 5% on average. The developed method was confirmed on nine different lyophilized fish samples which contained 6.1-26.5% lipid (dry mass based), and native CB concentrations in the range 0.8-134 ng/g.