Comprehensive Mass Spectrometry Workflows to Systematically Elucidate Transformation Processes of Organic Micropollutants: A Case Study on the Photodegradation of Four Pharmaceuticals

Organic micropollutants (OMPs) in the aquatic environment
challenge
conventional water treatment processes. Advanced oxidation processes,
such as UV photolysis, serve as effective strategies to remove OMPs.
However, these often yield unknown transformation products (TPs).
High-resolution mass spectrometry (HRMS)-based non-target analysis
(NTA) is commonly used to screen large numbers of chemicals but faces
specific challenges such as low concentrations of compounds of interest,
lack of reference standards, and the need for sophisticated data analysis
workflows when used for TP identification. This article describes
comprehensive workflows to study UV photolysis-related processes and
the resulting TPs, by combining an automated photodegradation setup
and HRMS and advanced NTA approaches. Four pharmaceuticals were successfully
degraded in a case study, and 38 NTA features were effectively prioritized
from complex sample matrices and identified as TPs through complementary
approaches developed in this work. The identified TPs were structurally
diverse and mostly novel. Semi-quantitation suggested that the TPs
explained a relevant part of the parent removal. The developed workflows
are a step toward systematic comprehensive analysis of transformation
processes in water and beyond. The openly available data-processing
tools and data enhance transformation data repositories and algorithms
and support NTA studies in general.