Development of a chromatographic method to study oxidative potential of airborne particulate matter

Abstract

Abstract. Oxidative potential (OP) is a measure of inhalation toxicity of airborne particulate matter (PM). The redox-active constituents of PM react with lung antioxidants (AOs) in the epithelial lining fluid (ELF), resulting in oxidation of AOs. The excessive loss of AOs leads to oxidative stress, inflammation of the epithelial tissue, and chronic diseases. In this work, we developed a novel rapid chromatographic method, employing an ultra-high performance liquid chromatograph coupled to a triple-quadruple mass spectrometer (UHPLC-MS/MS), to determine the OP of ambient PM, and investigated the application of electrochemical oxidation-reduction potential (ORP) as an alternative approach for estimating OP. We measured the direct oxidation of AOs, ascorbic acid, glutathione, and cysteine, and formation of glutathione disulfide and cystine, following PM addition to various simulated ELF (SELF) formulations which, in addition to AOs, contained inorganic salts, a phospholipid, and proteins. The assay performance was evaluated using standard reference PM, and we investigated the links between OP dose-response, time-dependence, and the ORP. The new assay showed a high precision, and when applied to PM, OP and ORP increased with both reaction time and PM concentrations in SELF. The presence of SELF inorganic species and surfactant lipid increased the OP determined through oxidation of glutathione and cysteine, but showed an opposite effect with ascorbic acid. The presence of proteins did not affect the OP. The findings suggest that ORP measurement could be used as an alternative and simple approach for estimating the OP of ambient PM.