Quenchers in advanced oxidation technologies for analysis of micropollutants by liquid chromatography coupled to mass spectrometry: Sodium sulphite or catalase? Ana M. Gorito a , Marta O. Barbosa a , C. Marisa R. Almeida b , M. Fernando R. Pereira a , Adrián M.T. Silva a , Ana R.L. Ribeiro a, ⁎ a Laboratory of Separation and Reaction Engineering, Laboratory of Catalysis and Materials (LSRE-LCM), Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal b Interdisciplinary Centre of Marine and Environmental Research (CIIMAR/CIMAR), Universidade do Porto, Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos s/n, 4450-208 Matosinhos, Portugal HIGHLIGHTS • Sodium sulphite is not recommended as quencher in AOTs when using LC-MS/ MS. • Catalase should be used as quencher of H 2 O 2 , when analysing by LC-MS/MS. • Matrix matched analytical validated methods are always recommended. • Analytical method validation must con- sider all the experimental steps of AOTs. GRAPHICAL ABSTRACT abstract article info Article history: Received 22 February 2019 Received in revised form 17 July 2019 Accepted 17 July 2019 Available online 18 July 2019 Editor: Ching-Hua Huang This work aimed to investigate the possible effect of 2 quenchers commonly used in H 2 O 2 -based advanced oxi- dation technologies (AOTs), i.e. catalase and sodium sulphite (Na 2 SO 3 ), on the analytical signal of 3 detectors coupled to liquid chromatography (LC): tandem mass spectrometry (LC-MS/MS), fluorescence detection (LC- FD) and LC-diode array detection (LC-DAD). The observation of analytical interferences for a group of compounds when studying the removal by continuous mode UV/H 2 O 2 of 26 micropollutants (MPs) from a spiked surface water (SW), for which the residual H 2 O 2 in the samples was quenched by Na 2 SO 3 , triggered the need of under- standing these effects and thus catalase was used as comparative quencher. From the 26 MPs having a wide range of polarity and pK a , those monitored after electrospray ionization (ESI) under positive ionization (PI) mode and presenting a pK a higher than 5.9 revealed a great signal suppression, but only when using Na 2 SO 3 as H 2 O 2 quencher. In this sense, we further explored this effect by selecting 2 MPs, metoprolol and diclofenac, which had respectively signal suppression and no interference in the LC-MS/MS response. These MPs were analysed be- fore and after addition of H 2 O 2 and catalase or Na 2 SO 3 in reaction vials, using: (i) different detectors coupled to Keywords: Matrix effects Hydrogen peroxide Sodium sulphite Fenton Science of the Total Environment 692 (2019) 995–1004 ⁎ Corresponding author. E-mail address: ritalado@fe.up.pt (A.R.L. Ribeiro). https://doi.org/10.1016/j.scitotenv.2019.07.278 0048-9697/© 2019 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv