Concentration and biotoxicity assay of dilute aqueous solutions of volatile chlorinated organics using supercritical fluid extraction

Abstract Chlorinated volatile organic compounds (VOCs) were extracted from dilute aqueous samples into methanol to provide sufficient concentration for bacterial toxicity measurements. Using equipment designed to prevent loss of volatiles, standards and biological reactor effluents were filtered, adsorbed onto XAD‐2 resin, extracted using supercritical carbon dioxide, and cryotrapped in liquid nitrogen with methanol as a keeper solvent for toxicity measurements using the Microtox bioassay system. The levels of 15 VOCs were increased 7–36 times in the methanol concentrates over the aqueous concentrations which ranged from 5 to 100 μg/L. Mass recoveries averaged 76%. Using this system, the effluent of an anaerobic bioreactor treating a complex mixture of chlorinated organics was found to be significantly less toxic than the influent (46% less), but the toxicity of the total organic halide fraction increased by 80%.