Abstract
The number of chemicals with potential to reach the environment is still largely unknown, which poses great challenges for both environmental scientists and analytical chemists. Liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) is currently the instrumentation of choice for identification of wide-scope polar chemicals of concern (CECs) in water. This review critically evaluates all steps involved in screening for polar CECs in water, including sampling and extraction, analysis by LC-HRMS, data (pre-)treatment, evaluation and reporting. Passive samplers and direct injection, in combination with LC-HRMS, provide new opportunities compared with conventional grab water sampling, as do instrumental advances such as ion-mobility spectrometry coupled to HRMS (IM-HRMS). In this paper, we argue that target, suspect and non-target screening should not be viewed as three separate principles, but rather as conceptual approaches to general data treatment strategies that can be linked together. Due to the large amount of data generated, smart prioritisation strategies are needed, in particular for non-target screening, to reduce complexity and focus on data of high interest. We critically evaluate existing strategies and consider that each prioritisation step will result in data loss (as any other step in a screening study), requiring compromises depending on the research question to be tackled. Many different data treatment strategies have been developed in recent years, but structure elucidation remains a challenging and time-consuming task. We discuss current and potential future trends, e.g. effect-based methods that can be used as future prioritisation tools, technological advances like IM-HRMS and improved software solutions that can enable new data treatment strategies.
Highlights
With the development of high-resolution accurate mass spectrometry (HRMS), a whole new field opened up within analytical chemistry, providing new opportunities for analysis of organic substances [1,2]
This paper presents a critical review of reported screening approaches using liquid chromatography (LC)-HRMS to analyse polar and semi-polar organic contaminants in water, including marine and fresh water, groundwater, drinking water, stormwater, landfill leachate, and wastewater treatment plant (WWTP) influent and effluent
We propose standardised use of these terms, to avoid misunderstanding and improve clarity, with the term ‘non-target screening’ referring only to conceptual data treatment approaches that do not consider structural information from the start, and alternative terms like ‘nontarget analysis’, ‘untargeted screening’ or ‘untargeted analysis’ being used for studies generally based on HRMS data acquired by untargeted data acquisition methods (e.g. dependent acquisition (DDA) and data-independent acquisition (DIA))
Summary
With the development of high-resolution accurate mass spectrometry (HRMS), a whole new field opened up within analytical chemistry, providing new opportunities for analysis of organic substances [1,2]. This paper presents a critical review of reported screening approaches using LC-HRMS to analyse polar and semi-polar organic contaminants in water, including marine and fresh water (lake, river), groundwater, drinking water, stormwater, landfill leachate, and WWTP influent and effluent. It covers i) sampling and sample treatment, ii) instrumental methods using LC-HRMS, iii) data preprocessing, iv) conceptual approaches, v) prioritisation strategies and vi) structure elucidation and validation. It comprehensively compiles and critically questions available instrumentation, tools and strategies at every stage of a water screening study aimed at CECs using LC-HRMS.
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