AN IMPROVED NON-TARGET ANALYSIS AND SUSPECT SCREENING WORKFLOW FOR ORGANIC ACID CONTAMINANTS IN DRINKING WATER

A novel and generalisable analytical workflow for non-target analysis (NTA) and suspect screening (SS) of organic acids in drinking water is presented, featuring selective extraction by silica-based strong anion exchange solid-phase extraction (SAX-SPE), mixed-mode liquid chromatography-high resolution mass spectrometric (LC-HRMS) analysis, non-targeted peak detection, features reduction and SS. To achieve this, a selection of 23 structurally diverse compounds with a broad range of polarities were evaluated. Importantly, the novel introduction of an elution solvent containing ammonium bicarbonate extended the current applicability of SAX-SPE for strong acids and subsequent mass spectrometry analysis. This new method performed with consistently higher recovery (88 ± 7 % at 500 ng L-1), improved selectivity and lower matrix interference (mean = 12%) over a generic mixed-mode weak anion exchange SPE method. In addition, a novel filter for reducing full-scan features from fulvic and humic acids was successfully introduced, reducing workload and potential for false positives. The workflow was then applied to NTA/SS of 10 London municipal drinking water samples, allowing the identification of 26 confirmed substances including several poorly investigated and potentially harmful compounds. In particular, predicted mutagenicity and occurrence frequency indicated the need for further investigation of halogenated hydroxy-cyclopentene-diones (HCDs) and dibromomethanesulfonic acid in drinking water. Overall, this approach demonstrated that employing some selectivity for general molecular properties in NTA overall helped shortlist suspect and potentially toxic chemical contaminants with higher confidence, in this case for organic acids.