Quantitative high-resolution gas chromatography and mass spectrometry of toxaphene residues in fish samples

This report describes an analytical method which permits the determination of ppb (1 microgram/kg) level of toxaphene in fish tissues. Interferences both from biogenic and from xenobiotic substances are reduced even with low-resolution mass spectrometry. The methodology has a low susceptibility to false positive determinations, which could result from the presence of a wide variety of co-contaminants. The method is based on the measurement of a signal representative of the toxaphene residue (m/z 158.9) relative to a known amount of an internal standard 37Cl-labelled compound. A modular approach to toxaphene enrichment has permitted a moderately simple procedure, significantly reducing analytical time requirements and the number of sample manipulations, and making the procedure amenable to automation. The reliability and accuracy of the procedure are demonstrated by the results of intra- and interlaboratory studies. The methodology has been validated and the presented data indicate that the detection limit is 1 microgra/kg of total toxaphene. Toxaphene recovery from fish at concentration levels between 0.1 and 10 micrograms/g is 84 +/- 12%.