Molecularly Imprinted Polymers for Compound-Specific Isotope Analysis of Polar Organic Micropollutants in Aquatic Environments

Compound-specific isotope analysis (CSIA) of polar organic micropollutants in environmental waters requires a processing of large sample volumes to obtain the required analyte masses for analysis by gas chromatography/isotope-ratio mass spectrometry (GC/IRMS). However, the accumulation of organic matter of unknown isotopic composition in standard enrichment procedures currently compromises the accurate determination of isotope ratios. We explored the use of molecularly imprinted polymers (MIPs) for selective analyte enrichment for C/C and N/N ratio measurements by GC/IRMS using 1 H-benzotriazole, a typical corrosion inhibitor in dishwashing detergents, as example of a widely detected polar organic micropollutant. We developed procedures for the treatment of >10 L of water samples, in which custom-made MIPs enabled the selective cleanup of enriched analytes in organic solvents obtained through conventional solid-phase extractions. Hydrogen bonding interactions between the triazole moiety of 1 H-benzotriazole, and the MIP were responsible for selective interactions through an assessment of interaction enthalpies and N isotope effects. The procedure was applied successfully without causing isotope fractionation to river water samples, as well as in- and effluents of wastewater treatment plants containing μg/L concentrations of 1 H-benzotriazole and dissolved organic carbon (DOC) loads of up to 28 mg C/L. MIP-based treatments offer new perspectives for CSIA of organic micropollutants through the reduction of the DOC-to-micropollutant ratios.