Gas-liquid chromatographic determination of chlorinated norbornene derivatives in fish

1,2,3,4,7,7-Hexachloro-2,5-norbornadiene (I), 1,2,3,4,5-endo,7,7-heptachloro-2-norbornene (II), and 1,2,3,4,7,7-hexachloro-5,6-endo-epoxy-2-norbornene (III) have been identified as contaminants in Mississippi River fish by combined gas-liquid chromatography (GLC)-mass spectrometry. The method used to determine residues of these compounds, which are associated with production of the pesticide endrin, is similar to the AOAC multiresidue method for chlorinated pesticides. The residues are extracted from the sample with acetonitrile, transferred to petroleum ether, and chromatographed on a Florisil column. Compounds I and II are eluted from the Florisil with petroleum ether and compound III is eluted with ethyl ether-petroleum ether (6 + 94). The concentrated eluates are analyzed by using electron capture GLC. The method provides adequate recoveries of all 3 chlorinated norbornene derivatives and allows quantitation at or below the 0.05 ppm level in fish with a 20 mg sample equivalent injection.