Critical review on the role of mass spectrometry in the AOP based degradation of contaminants of emerging concern (CECs) in water

Elimination of organic contaminants of emerging concern (CECs) from precious environmental resources is an important process for reducing adverse effects to living species. Advanced oxidation processes (AOPs) have already been adopted by many researchers to detoxify several CECs. However, hydroxyl (OH) radical reaction, the primary degradation mechanism in most AOPs, with CECs might generate structurally (and possibly toxicologically) similar transformation products. In-depth mechanistic investigations are, therefore, required before adapting AOPs for real water purification purposes. Mass spectrometry (MS)-based transformation product studies, either alone or in combination with a suitable chromatographic technique, has extensively been utilized to achieve this crucial information. In this report, we reviewed recent mass spectrometry-based investigations conducted to explore the degradation mechanism of CECs by various AOPs. The importance and advantages of conducting mass spectrometric studies along with any AOPs to eliminate CECs are thoroughly discussed. Further, the traditional (targeted) and newly emerged (non-targeted) MS approaches are briefly compared. The prime focus of this review is devoted to explain how the scientific community utilised the results obtained from the cutting-edge MS techniques, such as high-resolution mass spectrometry (HRMS), to explore the degradation mechanism of CECs. The MS-based mechanistic approaches, an extremely important, but under explored area related with the widely used advanced oxidation and related wastewater purification plants, discussed in this review might be utilized as a reference data for the implementation of AOPs into real environment uses. [Display omitted] •Advanced oxidation processes (AOPs) are effective ways to degrade contaminants of emerging concern (CECs).•The extensive role of mass spectrometry (MS) in AOP has been reviewed.•MS use at different stages helps to identify toxic products formed during the course of degradation.•Combining computational calculations with MS data enhances the accuracy.•High-resolution mass spectrometric (HRMS) analyses are highly recommended as a prerequisite for any AOP based degradation.