The aim of this work was to develop and apply a comprehensive workflow for NTA of organic acids and to help identify potentially new toxic substances from this class in municipal drinking water with high confidence. The objectives included design, optimisation, evaluation and application of the sample preparation, instrumental analysis, peak detection, feature reduction and suspect screening stages using, initially, 23 selected hazardous organic acid substances followed by wider application to NTA and SS of drinking water samples from London, UK. Specifically, we present the novel use of SAX-SPE employing a high ionic strength elution solvent (ammonium bicarbonate) which can be eliminated conveniently before LC-HRMS for detection of both weak and strong organic acids. Additionally, a new RP-WAX LC-HRMS method was developed to separate organic acids with a broad range of polarities (LogD at pH 7.5 ranging from 3.6 to -3.9, Table , predicted with ACD/Labs Percepta). Lastly and importantly for NTA of acids in drinking water, a list of known elemental compositions present in drinking and surface water DOM was generated and to our knowledge, this is the first time such a list has been employed for feature reduction in NTA/SS. Overall, this new approach can be used to improve confidence of detection and identification of new acidic and potentially toxic agents in drinking water.