A method for quantifying C 10 -C 13 polychloroalkanes (PCAs) in environmental samples by high-resolution gas chromatography/electron capture negative ion highresolution mass spectrometry in the selected ion monitoring (SIM) mode is presented. The molecular compositions of commercial PCAs and of PCA-containing extracts from environmental samples are first determined by monitoring [M -Cl] -ions of specific m/z value corresponding to formula groups present and by assuming that the integrated ion signals are proportional to molar concentration weighted by the number of chlorine atoms in the formula group. For quantitative measurement, one specific m/z peak is selected for each analyte and its SIM response is integrated. The integrated SIM responses have a linear dependence upon amount of PCA injected over the range 0.5-500 ng. An analytical protocol is then described. High-resolution (∼12 000 resolving power) mass spectrometry is shown to be desirable to eliminate self-interferences between PCAs at low resolving power (∼1000) and potential interferences from technical chlordane, toxaphene, PCBs, and other organochlorine pesticides. Extraction recoveries of PCAs from fish averaged

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Marine mammals from various regions of the Arctic and the St. Lawrence River estuary were examined for the first time for levels of C 10 -C 13 polychloro-n-alkanes (sPCAs). Respective mean total sPCA concentrations in the blubber of beluga whales (Delphinapterus leucas) from Saqqaq and Nuussuaq, western Greenland, were 0.23 ( 0.02 (n ) 2) and 0.164 ( 0.06 µg/g (n ) 2), similar to that in beluga from the Mackenzie Delta in the western Canadian Arctic 0.21 ( 0.08 µg/g (n ) 3). sPCAs levels were higher in beluga blubber from the St. Lawrence River (0.37 to 1.4 µg/g). Mean sPCA concentrations in the blubber samples from walruses (Odobenus rosmarus) (Thule, northwest Greenland) and ringed seal (Phoca hispida) (Eureka, southwest Ellesmere Island) were 0.43 ( 0.06 (n ) 2) and 0.53 ( 0.2 µg/g (n ) 6), respectively. Relative to commercial sPCA formulations, samples from the Arctic marine mammals showed a predominance of the shorter chain length lower percent chlorinated PCA congeners, the more volatile components of industrial formulations. This observation is consistent with long-range atmospheric transport of sPCAs to this region. The profiles of the belugas from the St. Lawrence River estuary, however, had higher proportions of the less volatile sPCA congeners, implying that contamination to this region is probably from local sources.