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

Abstract

Enrichment methods used in sample preparation for the bioanalytical assessment of disinfected drinking water result in the loss of volatile and hydrophilic disinfection byproducts (DBPs) and hence likely tend to underestimate biological effects. We developed and evaluated methods that are compatible with bioassays, for extracting nonvolatile and volatile DBPs from chlorinated and chloraminated drinking water to minimize the loss of analytes. For nonvolatile DBPs, solid-phase extraction (SPE) with TELOS ENV as solid phase performed superior compared to ten other sorbents. SPE yielded >70% recovery of nonpurgeable 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 nonpurgeable 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 nonpurgeable 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 nonpurgeable fraction is dominated by unknown DBPs.

Bioanalytical assessment of adaptive stress responses in drinking water: A predictive tool to differentiate between micropollutants and disinfection by-products

“…based on the detected DBPs, with EC IR1.5 values for the individual detected DBPs collected from Stalter et al (2016a) (provided in Table S1). This approach is justified because Stalter et al (2016b) demonstrated that the BEQ chem, volatile stems mainly from known DBPs, though it should be noted that not all known volatile DBPs were analysed in the current study. BEQ bio was also compared with BEQ chem, non-volatile for chemicals with a Henry's Law…”

“…However, this was not observed for the targeted DBPs. Different sample preparation methods were used for chemical analysis and bioanalysis, with sample enrichment for bioanalysis mainly extracting non-volatile and semi-volatile DBPs, while chemical analysis mostly targeted volatile DBPs (Stalter et al 2016b). Therefore, formation of undetected non-volatile or semi-volatile DBPs may explain the increased effect in September.…”

“…The BEQ concept was also applied to determine the contribution of volatile DBPs. As volatile DBPs are not captured by typical sample enrichment processes used for bioanalysis and the effects in the volatile fraction are typically well explained by the known volatile DBPs (Stalter et al 2016b), forty non-volatile and volatile DBPs including haloacetic acids (HAA), haloacetonitriles (HAN) and trihalomethanes (THM) were quantified by gas chromatography with electron capture detector (GC-ECD) and gas chromatography with mass spectrometry (GC-MS). Using the detected concentrations and the relative effect potency of the individual DBPs in the assays, bioanalytical equivalent concentrations from detected chemical concentrations (BEQ chem ) were calculated for volatile and non-volatile DBPs, which were then compared to BEQ bio .…”

Waterworks-specific composition of drinking water disinfection by-products

“…Bioluminescence inhibition assays indicate that DBPs in the non-purgeable fraction (in the specific study defined as the total amount of adsorbed organic halogens (AOX) present after purging the sample with nitrogen for 30 minutes) are of higher toxicological relevance than DBPs in the purgeable fraction. 12 In the same study, AOX and a range of known DBPs were analysed. Most of the AOX in the purgeable fraction, i.e.…”

“…non-volatile to semi volatile compounds, demonstrating the lack of available information of DBPs in this pool. 12 Recent work summarizing the challenges and opportunities within DBP research points towards the need of finding the key "toxicity drivers" that can explain the observed risk for bladder cancer, so that efforts to minimize exposure focus on the relevant targets. 13 A number of studies have been carried out to analyze the non-volatile fraction of DBPs using nontarget approaches, where some have focused on lab experiments, [14][15][16][17][18] and a few on real waterworks.…”