Electrochemistry-High Resolution Mass Spectrometry to Study Oxidation Products of Trimethoprim

Abstract

Abstract:The study of the fate of emerging organic contaminants (EOCs), especially the identification of transformation products, after water treatment or in the aquatic environment, is a topic of growing interest. In recent years, electrochemistry coupled to mass spectrometry has attracted a lot of attention as an alternative technique to investigate oxidation metabolites of organic compounds. The present study used different electrochemical approaches, such as cyclic voltammetry, electrolysis, electro-assisted Fenton reaction coupled offline to high resolution mass spectrometry and thin-layer flow cell coupled online to high resolution mass spectrometry, to study oxidation products of the anti-infective trimethoprim, a contaminant of emerging concern frequently reported in wastewaters and surface waters. Results showed that mono-and di-hydroxylated derivatives of trimethoprim were generated in electrochemically and possibly tri-hydroxylated derivatives as well. Those compounds have been previously reported as mammalian and bacterial metabolites as well as transformation products of advance oxidation processes applied to waters containing trimethoprim. Therefore, this study confirmed that electrochemical techniques are relevant not only to mimic specific biotransformation reactions of organic contaminants, as it has been suggested previously, but also to study the oxidation reactions of organic contaminants of interest in water treatment. The key role that redox reactions play in the environment make electrochemistry-high resolution mass spectrometry a sensitive and simple technique to improve our understanding of the fate of organic contaminants in the environment.

Transformation Products of Organic Contaminants and Residues—Overview of Current Simulation Methods

“…For these methods, only a low concentrated test substance can be used and, consequently, less amounts of metabolites are generated. The biotransformation process is initiated by a single electron transfer or hydrogen atom transfer involving an iron–oxygen complex [ 18 ]. Major CYP450 catalyzed reactions are oxidations like carbon hydroxylation, heteroatom dealkylation, heteroatom oxygenation, bond oxidation, hydrocarbon desaturation, dehalogenation, and epoxidation [ 1 , 16 , 19 ].…”

“…The electrochemical oxidation, which occurs by applying a potential, lead to comparable reactions like phase I reactions of the biotransformation process. Ultimately, EC mimics reactions initiated by a single-electron transfer like N -dealkylation, S - and P -oxidation, alcohol oxidation, dehydrogenation reactions, hydroxylation of activated aromatic compounds, and dehalogenation [ 18 , 20 , 22 ].…”

“…The photo-Fenton generated the other five TPs (TP4: opening β-lactam ring, TP5 breakdown of the central secondary amide, TP6: S -oxidation, TP7: aromatic hydroxylation, TP8: opening β-lactam ring, and TP9: decarboxylation), three of them are also observed with photocatalysis (TP5, TP7, and TP8) and sonochemistry (TP4, TP5, and TP6). Another study by Lecours et al compared electrolysis, EC-Fenton, and EC-reactor methods for the simulation of TPs of Trimethoprim [ 18 ]. The α-OH-Trimethoprim as TP was simulated with all three methods and is described in the literature as a metabolite of rat models.…”

“…To predict and investigate TPs occurring in the environment, photolytic, and photocatalytic experiments are widely used. However, there are also a few studies where electrochemistry methods are used in the environmental science [ 18 ] and photolytic/photocatalytic experiments to simulate in vivo or in vitro metabolites [ 70 , 74 ]. Typical metabolic redox reactions can be mimicked with most of the above described simulation methods.…”

New Methodology for the Identification of Metabolites of Saccharides and Cyclitols by Off-Line EC-MALDI-TOF-MS

“…This simple instrumental analytical technique allows the production, detection, and identification of a number of metabolic products, including reactive intermediate metabolites, that are responsible for drug activation. EC/MS also allows the identification of the final products of electrochemical reactions of the tested compounds and is used in redox (oxidation-reduction) studies [24][25][26].…”