Sample Enrichment for Bioanalytical Assessment of Disinfected Drinking Water: Concentrating the Polar, the Volatiles, and the Unknowns

Daniel Stalter, Leon I. Peters, Elissa O’Malley, Janet Yat-Man Tang, Marion Revalor, Maria José Farré, Kalinda Watson, Urs von Gunten, Beate I. Escher

Enrichment methods used in sample preparation for the bioanalytical assessment of disinfected drinking water result in the loss of volatile and hydrophilic disinfection by-products (DBPs) and hence likely tend to underestimate biological effects. We developed and evaluated methods that are compatible with bioassays, for extracting non-volatile and volatile DBPs from chlorinated and chloraminated drinking water to minimize the loss of analytes. For non-volatile DBPs, solid-phase extraction (SPE) with TELOS ENV as solid phase performed superior compared to ten other sorbents. SPE yielded >70% recovery of non-purgeable adsorbable organic halogens (AOX). For volatile DBPs, cryogenic vacuum distillation performed unsatisfactorily. Purge and cold-trap with crushed ice serving as condensation nuclei achieved recoveries of 50-100% for trihalomethanes and haloacetonitriles and approximately 60-90% for purged AOX from tap water. We compared the purgeable versus the non-purgeable fraction by combining purge-and-trap extraction with SPE. The purgeable DBP fraction enriched with the purge-and-trap method exerted a lower oxidative stress response in mammalian cells than the non-purgeable DBPs enriched with SPE after purging, while contributions of both fractions to bacterial cytotoxicity was more variable. 37 quantified DBPs explained almost the entire AOX in the purge-and-trap extracts but <16% in the SPE extracts demonstrating that the non-purgeable fraction is dominated by unknown DBPs.