Polar organic chemical integrative sampler (POCIS) allows compound specific isotope analysis of substituted chlorobenzenes at trace levels

Compound specific isotope analysis (CSIA) is an established tool to demonstrate in situ degradation of traditional groundwater contaminants at heavily contaminated sites, usually at mg/L range aqueous concentrations. Currently, an efficient preconcentration method is lacking to expand CSIA to low aqueous concentration environmental samples. This work demonstrated the compatibility of polar organic chemical integrative sampler (POCIS) with CSIA of C, H, and N isotopes for four NH2- and NO¬2-substituted chlorobenzenes at low μg/L. Diffusion and sorption showed insignificant carbon isotope fractionation (<0.7‰) in laboratory experiment, except for a reproducible shift of 1.6‰ for 3,4-dichloronitrobenzene. A similar constant reproducible shift of 0.8-2‰ was evident for N-CSIA. Whereas, the compatibility of POCIS for H-CSIA seems to be analyte specific possibly reflecting the adsorption mechanism to POCIS by H-bonding. Performance of the POCIS-CSIA method was evaluated in a pilot constructed wetland where comparable C- and N-CSIA results were obtained from grab sampling and POCIS. This work opens the potential of CSIA application to the low concentration polar emerging contaminants in the environment, such as pesticides, pharmaceuticals, and flame-retardants.