Conversion of chlorinated volatile organic compounds to carbon dioxide and methyl chloride for isotopic analysis of carbon and chlorine

A nonaqueous, high-temperature method is described for converting micromole quantities of chlorinated volatile organic compounds to CO2 and CH3Cl for C and Cl isotope ratio determinations. This method provides an improved analytical approach for using C and CI isotope ratios in studies of the biodegradation of chlorinated volatile organic compounds in the environment. Conversion of reagent CH3Cl to CO2 + CuCl and then conversion of the CuCl back to CH3Cl by the present method gives typical yields of 99 +/- 1% for CO2 and 91 +/- 1% for CH3Cl, both products of >99% purity. An offset of -0.23 +/- 0.05 parts per thousand is observed between the Cl-37/Cl-35 ratios of product and initial CH3Cl. Precision of the isotopic ratio measurements is better than +/- 0.1 parts per thousand for a variety of chlorinated volatile organic compounds.