An integrated approach to MS-based identification and risk assessment of pharmaceutical biotransformation in wastewater

The omnipresence of pharmaceuticals at relatively high concentrations (mu g/L) in environmental compartments indicated their inadequate removal by wastewater treatment plants. As such, batch reactors seeded with activated sludge were set up to assess the biotransformation of metformin, ranitidine, lidocaine and atorvastatin. The main objective was to identify transformation products (TPs) through the establishment of an integrated workflow for suspect and non-target screening based on reversed phase liquid chromatography quadrupoletime-of-flight mass spectrometry. To support the identification, hydrophilic interaction liquid chromatography (HILIC) was used as a complementary tool, in order to enhance the completeness of the developed workflow by identifying the more polar 1 Ps. The structure assignment/elucidation of the candidate TPs was mainly based on interpretation of MS/MS spectra. Twenty-two TPs were identified, with fourteen of them reaching high identification confidence levels (level 1: confirmed structure by reference standards and level 2: probable structure by library spectrum match and diagnostic evidence). Finally, retrospective analysis in influent and effluent wastewater was performed for the TPs for four consecutive years in wastewater sampled in Athens, Greece. The potential toxicological threat of the compounds to the aquatic environment was assessed and atorvastatin with two of its TPs showed a potential risk to the aquatic organisms. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study investigated the inadequate removal of pharmaceuticals by wastewater treatment plants, evaluated the biotransformation of four drugs using batch reactors, and identified 22 transformation products through various mass spectrometry techniques. The results revealed that some transformation products may pose a potential risk to aquatic organisms.