When organic matter in environmental water matrices interacts with oxidants such as chlorine, chloramine, or ozone, toxic oxidation byproducts (OBPs) are generated. These OBPs are typically electrophilic compounds, and one mechanism of toxicity is through their covalent binding to electron-rich bionucleophiles such as amines and thiols (e.g., lysine/cysteine residues and glutathione). Unfortunately, many of these OBPs escape conventional analytical approaches such as solid-phase extraction (SPE) followed by liquid chromatography-high resolution mass spectrometry (LC-HRMS) due to their low molecular weights, high polarity, high volatility, and/or poor ionizability during electrospray ionization. As a result, the majority of OBPs responsible for the toxicity of treated waters remain unidentified. For this reason, the analytical platform Solid-Phase Reactivity-directed Extraction (SPREx) has recently been developed for simultaneous in chemico toxicity screening, extraction, detection, and identification of toxic organic electrophiles produced during water treatment processes. SPREx involves the use of nucleophile-labeled microbeads to serve the purpose of being an in chemico toxicity prioritization probe as well as a derivatization agent. Nucleophile-electrophile stable adducts are formed on cleavable microbeads to increase the overall adducts’ molecular weights and ionizability for compatibility with LC-HRMS analysis and subsequent identification. The solid-phase microbeads in SPREx enable an improved extraction method compared to previous approaches such as SPE for the preconcentration of OBP analytes. In addition, the extraction approach via solid-phase nucleophile beads allows for a variety of sample matrices to be tested and removed prior to LC-HRMS analysis. To demonstrate the advantages and limitations of this method, SPREx has been applied for both the targeted and nontargeted screening of OBPs in various environmental water matrices treated with oxidants such as chlorine. This novel method is one of the few in chemico approaches utilized for the screening and identification of OBP mixtures in water treatment applications.

Daisy Grace

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