Oxidation in Mass Spectrometry: Applications in Analyte Detection in Complex Mixtures

The use of mass spectrometry in complex mixture analysis has had a profound impact on the way researchers approach scientific investigations. Although this versatile analytical tool can provide insight into the composition of a sample, mass spectrometric data can often be influenced by oxidation resulting from either the sample itself or chemical transformations that occur during ionization (i.e., biological oxidation and in-source oxidation, respectively). Oxidation can yield complex mass spectra that comprise unexpected ions and, ultimately, prevent the accurate characterization of components in a sample. In some instances, however, oxidation in mass spectrometry may be used advantageously in the analysis of hard-to-detect analytes. In the current work, various studies involving oxidation in mass spectrometry are discussed. Specifically, a fundamental investigation on the in-source oxidation of hydrocarbons was performed to explain the mechanism by which these transformations occur. This study presents a novel mechanism for in-source oxidation, for which few proposed mechanisms exist. An analysis of compounds that are more prone to in-source oxidation (i.e., sulfur-containing metabolites) was performed by mitigating chemical transformations through derivatization, allowing the proper characterization of a metabolic cycle in which readily oxidizable metabolites are essential. The downstream effects of biological oxidation were investigated in malnourished mammals through the use of various metabolite and lipid profiling methods. These investigations promoted the phenotyping of malnourished versus healthy subjects. Finally, novel graphical algorithms were developed and explored to evaluate signs of oxidation in the lipidome. This investigation yielded a promising data visualization technique that can distinguish oxidized lipids, as well as lipid classes. The collection of these studies not only advances the understanding of oxidation in mass spectrometry, but also expands the potential applications for utilizing or mitigating these chemical transformations in complex mixture analysis.