A congener-specific method for the quantification of camphechlor (toxaphene) residues in fish and other foodstuffs

To develop a method for the quantification of camphechlor without the use of complex technical toxaphene as gas-chromatographic standard, all important chlorobornane peaks have been identified in a mixed marine fish sample reflecting the fish consumption in Germany. Further ECD but not ECNI-MS has been found to be suitable for estimation of the relative concentrations of chlorobornanes. The three camphechlor congeners with the highest ECD response have been found in concentrations of 0.05-0.08 mg/kg (fat basis), representing about 50% of the total chlorobornanes present. A predominance of these congeners has also been observed in a standard reference material of cod liver oil (SRM 1588). As these three congeners are presumed to be dominant in human camphechlor intake, it is proposed to use them as indicator components for a congener-specific analysis of camphechlor residues together with a fourth heptachlorobornane which does not accumulate in fish. Cleanup by gel permeation and silica gel chromatography with GC/ECD analysis has been tested for its suitability to determine these camphechlor congeners. The limit of determination found for each congener was about 5 mu g/kg. The determination of these four congeners allows an unambiguous identification without specific cleanup (e.g. complete separation from PCBs or chlordanes) and a simple quantification of camphechlor residues, thus eliminating systematic errors resulting from different technical standards or detectors.