Airborne concentrations of toxaphene congeners at Point Petre (Ontario) using gas-chromatography-electron capture negative ion mass spectrometry (GC-ECNIMS).

A reliable analytical method has been developed using GC-ECNIMS for the determination of individual toxaphene congeners in ambient air. To allow a reasonable comparison with previous data for toxaphene reported by Muir and co-workers using GC-ECD, this method has adopted their approach of focussing upon the identification and quantification of specific peaks or clusters ("T" species) typically observed in environmental samples, with the sum of these "T" species then being reported as "total toxaphene". Technical toxaphene has been used as the analytical standard, but independent response factors have been assigned to the target peaks and clusters. Because of the appreciable variability in ECNIMS response shown by individual toxaphene congeners, this is considered to be a reasonable and potentially more accurate procedure than the application of a "single response factor" used by many other workers. The methodology has been used for the determination of toxaphene in air samples collected over the annual cycle in 1992 and then from October 1995 to September 1997 at Point Petre, Ontario. Of the forty-four calibrated components, only 10 were detected in all of the air samples collected over the latter 2-year period. Airborne concentrations of toxaphene (defined as the sum of the calibrated components) range from 0.9 pg/m3 to 10.1 pg/m3. A clear seasonality has been observed, with a summer-to-winter concentration ratio of about 6.