Methods for the Stable Isotopic Analysis of Chlorine in Chlorate and Perchlorate Compounds

Chlorate and perchlorate compounds, used as herbicides, solid fuel propellants, and explosives, arc increasingly recognized as pollutants in groundwater. Stable isotope characterization would permit both environmental monitoring of extent of remediation and forensic characterization. Stoichiometric reduction to chloride (greater than 98% yield), by Fe(II) for chlorate and alkaline fusiondecomposition for perchlorate, allows analysis by standard methods to give highly reproducible and accurate delta^37Cl results (0.05%o, 2 x standard error). Analysis of various compounds from different suppliers yielded delta^37CI values for chlorate samples near to +0.2% (SMOC), but one has within-sample heterogeneity of 0.5%o, possibly due to crystallization processes during manufacture. Results for perchlorate samples also are generally near +0.2%, but one is +2.3% (SMOC). The initial results suggest that both forensic and environmental applications might be feasible.