Sequential determination of chlorine and carbon isotopic composition in single microliter samples of chlorinated solvent

Chlorinated hydrocarbons, significant environmental pollutants, may be characterized by stable isotopic compositions of carbon and chlorine. Previously published analytical methods needed separate preparations for carbon and chlorine and were not ideal for environmental studies because of low sensitivity and precision. This method quantitatively extracts both carbon and chlorine from a single aliquot of chlorinated solvent of a size practical applicable to natural systems, Samples of 1-2 mu L of chlorinated solvent are combusted in sealed tubes with cupric oxide at 620-820 degrees C. After separation of CO2 for isotopic analysis of carbon, the residue contains all the chloride in water-soluble form. It is then processed by conventional methods for chlorine isotopic analysis and gives a yield of 97 +/- 27% (SD) on standard trichloroethylene (TCE) and 97 +/- 4% on standard perchloroetlhylene (PCE) for the whole of the Cl preparation process. TCE and PCE laboratory standards show reproducibilities (SD) for both products of 0.08 parts per thousand for delta(13)C and 0.15 and 0.10 parts per thousand, respectively, for delta(37)Cl. The technique is applicable to all five types of chlorinated solvents investigated (TCE, PCE, dichloromethane, 1,1,1-trichloroethane, and chloroform) and was tested by application to apr environmental sample of a vacuum-extracted mixture of chlorinated solvents from a polluted site, giving excellent reproducibilities for both carbon and chlorine isotopic compositions (respectively +/-0.05 acid +/-0.08 parts per thousand).