Background

Metabolomics is a field of study aiming to comprehensively analyze metabolites through the use of various analytical detection methods, namely mass spectrometry (MS) and nuclear magnetic resonance (NMR) (Liu and Locasale, 2017). Although both NMR and MS are essential tools in metabolomics, mass spectrometry can analyze samples with greater sensitivity (Liu and Locasale, 2017). Within mass spectrometry, various approaches are available, however a rapid approach to profile the global metabolome is needed (Lv et al., 2011; Rhoades and Weljie, 2016). Advancements in triple quadrupole mass spectrometers have made them well suited for ion-switching methods (scanning in both positive and negative ion modes within a single analysis) in addition to enabling reproducible and sensitive targeted profiling of numerous metabolites (Lv et al., 2011; Gika et al., 2012; Yuan et al., 2012; Rhoades and Weljie, 2016). Additionally, LC typically does not require extensive sample preparation, nor derivatization, which allows for the detection of a broader range of metabolites (Gika et al., 2012; Liu and Locasale, 2017). Nonetheless, development of LC-MS methods to comprehensively analyze small polar metabolites is nontrivial, and requires advanced modeling to optimize both LC and MS factors simultaneously. Thus, the COLMeD approach aimed to address this challenge and enabled a more comprehensive metabolite analysis across platforms including on a triple quadrupole mass spectrometer (Rhoades and Weljie, 2016). The LC-MS workflow on a triple quadrupole is described here and has been used to successfully study metabolomics in a circadian context in which 179 metabolites were successfully profiled and analyzed (Krishnaiah et al., 2017).