Mass Spectrometry-Based Approaches to Improve Small Molecule Annotation and Analysis

Abstract

Mass spectrometry (MS)-based untargeted metabolomics studies aim to profile small molecules (<~1000 Da) to more fully understand their roles and impacts in various biological processes. However, due to the prevalence of isomers, isobars, and common fragmentation patterns, confidently identifying specific species proves to be a notable challenge. Ion mobility (IM) is a size-dependent gas phase separation technique that, when coupled with liquid chromatography (LC) pre-MS, can improve the separation of complex biological samples. Additionally, IM-derived values, the collision cross section (CCS), can be used in conjunction with retention time, accurate mass, and possible fragmentation data to better identify analytes. As LC-IM-MS workflows continue to be used, it is imperative to assess the impact of pre-mobility parameters, such as LC solvent composition and electrospray ionization (ESI) source parameters, on CCS to maintain the high reproducibility of these values in small molecule analysis. For a variety of drug and drug-like molecules, CCS values were measured in various solvent compositions, ESI gas temperatures, and in-source activation energies. Taken together, this dissertation summarizes efforts and recommendations toward the continued improvement in identification of small molecules using LC-IM-MS.