Rapid screening of fish tissue for polychlorinated dibenzo-p-dioxins and dibenzofurans

A rapid, simple method for screening polychlorinated dibenzo-p-dioxin and dibenzofuran classes in shellfish tissue at pg g–1 wet mass concentrations is described. The method does not require a clean room facility and is based on saponification followed by extraction into hexane, clean-up using gel-permeation chromatography and sulfuric acid treatment, and measurement using capillary gas chromatography–low resolution mass spectrometry with selected ion monitoring. Selected ion monitoring using multiple ions eliminates interferences not removed by clean-up or chromatography. The detector response factor is constant for isomers within a class, e.g., tetrachlorodibenzo-p-dioxin isomers gave a mean response of 0.977 ± 0.075 area counts fg–1, but varied significantly between classes. Thus one isomer serves as a ‘standard’ for all members of its class. Recoveries of added polychlorinated dibenzo-p-dioxins and dibenzofurans (20-500 pg g–1 wet mass) averaged 95.6 ± 6.9 and 99.0 ± 5.7%, respectively. The limits of detection (five times the noise level) are 20 pg g–1 tetrachlorodibenzo-p-dioxins and dibenzofurans, 20 pg g–1 pentachlorodibenzo-p-dioxins and dibenzofurans, 40 pg g–1 hexachlorodibenzo-p-dioxins and dibenzofurans, 40 pg g–1 heptachlorodibenzo-p-dioxins and dibenzofurans, and 100 pg g–1 octachlorodibenzo-p-dioxin and dibenzofuran. Above the limits of detection, the method gave results for polychlorinated dibenzo-p-dioxin and dibenzofuran classes in shellfish tissue comparable to those obtained by gas chromatography–high reolution mass spectrometry.