The mass spectrometric characterization of polychlorinated n-alkanes and the methodology for their analysis in the environment

The major objective of the research was to develop a method for sensitive and specific andysis of C,&, polychloroalkanes (PCAs) Ui environmental sarnples. Our method of choice became high resolution gas chromatography/electron capture negative ion high resolution mass spectrometry (HRGCIECNI-HRMS) in the selected ion monitoring (SLM) mode. 'Ine development of the method involved several steps: (a) Because commercial PCA preparations may contain several thousands of compounds, eight representative compounds of known structure were synthesized in order to examine tbeir chromatographie and mass spectral properties. (b) The electron ionization (EI) positive ion mass spectra, generated with a Kratos Concept (EBE geometry) mass spectrometer, were interpreted with the aid of unimolecular and collision assisted dissociation mass spectra, and enthalpy of formation and forcefield estirnates of strain energy of ions. (c) ECNI mass spectra were investigated under various ion sourcc conditions to find optimum parameters for sensitivity. (d) Based on these results, a profile of the components of significant abundance in the PCA is detemined by an ECM selected ion monitoring method. The profile cm be used not only for quantitative measurements but aiso for assessrnent of origin, mode of environmental transport, and biological modification of PCAs. (e) Finally, a quantitative analytical procedure was developed. The protocol has been applied to the quantification of PCAs in a wide variety of environmental sarnples fiom Canada and the United States. Total PCA concentrations (ZPCAs) in sediment sampies fkom the mouth of the Detroit River (Ml) (0.3 pgg) were higher than of CDDT (DDT plus metabolites) (0.19 pg/g) but lower than of ZPCBs (1.5 pg/g) and ZPCTs (2.5 @g). CPCA levels in yellow perch (1 -0 pg/g) were similar to XPCB ievels in silver bass (0.091.2pg/g) Mean mCA levels (n=5) in air sarnples fiom Egbert, Ont . , (44" 1 4' N, 79' 47' W), coliected in 1990, were 543 & 3 18 pg/m3, which is similar to ZPCB levels (74-682 pg/m3) reported =lier. The highest observed XPCA concentration of 924 pg/m3 was higher than the highest ZPCB concentration (2 = 9 1 congeners), 682 pg/m3. The mean ZPCA concentration for water collected over a six month period fiom Selkirk, MB, of 30 14 n& was significantly higher than that of ZPCBs (1.1 * 1.2 ngL). Concentrations of ZPCAs in beluga whales (Delphinapterus leucas) from the St. Lawrence River estuary were higher than in blubber samples fiom a variety of marine mamrnals fiom various regions of the Arctic; the similaritof its PCA composition to that of an industrial formulation suggests local source contamination. CPCAs îeveis were also cornpared to other organochlo~es. Sediment cores nom 4 Canadian lakes ranging from 49W to 8 1"N, were also analyzed for PCAs. Concentrations of total PCAs in surface sedirnents fiom Lake Winnipeg (5OW/96"W, Manitoba) and Hazen lake (8 1 W/7 1 W, High Arctic) were 176 and 4.5 nglg (w (dry), respectively; corresponding surficial flues were 147 and 0.9 pg/m2 yr. The high flux of PCAs to Lake W ' i p e g suggests local contamination. The su&ial flux of PCAs to Fox lake (6 1 W/ 135OW), a sub-arctic lake in theYukon, was also high, 34 pg/m' yr, but much lower in Lake Nipigon (49"N/890W, N.Ontario), 3 pg /m$. PCA concentrations were highest in sediment slices àated fiom the early 1980s to the 1990s, which is consistent with the usage patterns of PCAs. The change in congener profiles with increasing sediment depth observed in sedhents fiom Fox lake and Lake Winnipeg suggests that biodegradation has occurred. The detection of PCAs in lakes fiom both populated and remote regions suggests that these organochlorines, are widespread trace contaminaats of fieshater environments in Canada.