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 concen trations is described. The method does not require a clean room facili ty and is based on saponification followed by extraction into hexane, clean-up using gel-permeation chromatography and sulfuric acid treatme nt, and measurement using capillary gas chromatography-low resolution mass spectrometry with selected ion monitoring. Selected ion monitorin g using multiple ions eliminates interferences not removed by clean-up or chromatography. The detector response factor is constant for isome rs within a class, e.g., tetrachlorodibenzo-p-dioxin isomers gave a me an response of 0.977 +/- 0.075 area counts fg-1, but varied significan tly between classes. Thus one isomer serves as a 'standard' for all me mbers of its class. Recoveries of added polychlorinated dibenzo-p-diox ins and dibenzofurans (20-500 pg g-1 wet mass) averaged 95.6 +/- 6.9 a nd 99.0 +/- 5.7%, respectively. The limits of detection (five times th e noise level) are 20 pg g-1 tetrachlorodibenzo-p-dioxins and dibenzof urans, 20 pg g-1 pentachlorodibenzo-p-dioxins and dibenzofurans, 40 pg g-1 hexachlorodibenzo-p-dioxins and dibenzofurans, 40 pg g-1 heptachl orodibenzo-p-dioxins and dibenzofurans, and 100 pg g-1 octachlorodiben zo-p-dioxin and dibenzofuran. Above the limits of detection, the metho d gave results for polychlorinated dibenzo-p-dioxin and dibenzofuran c lasses in shellfish tissue comparable to those obtained by gas chromat ography-high reolution mass spectrometry.