Mass Spectrometry: A Guide for the Clinician

Abstract

Metabolic profiling, metabonomics and metabolomics are terms coined in the late 1990s as they emerged as the newest 'omics' technology at the time. This line of research enquiry uses spectroscopic analytical platforms, which are mainly nuclear magnetic resonance spectroscopy and mass spectrometry (MS), to acquire a snapshot of metabolites, the end products of a complex biological system. Metabolic profiling enables the detection, quantification and characterisation of metabolites in biofluids, cells and tissues. The source of these compounds can be of endogenous, microbial or exogenous origin, such as dietary or xenobiotic. This results in generating extensive, multivariate spectroscopic data that require specific statistical manipulation, typically performed using chemometric and pattern recognition techniques to reduce its dimensions, facilitate its biological interpretation and allow sample classification and biomarker discovery. Consequently, it is possible to study the dynamic metabolic changes in response to disease, intervention or environmental conditions. In this review, we describe the fundamentals of MS so that clinicians can be literate in the field and are able to interrogate the right scientific questions.

Keywords: CID, collision-induced dissociation; DC, direct current; ESI, electrospray ionisation; FC, fold change; GC, gas chromatography; HILIC, hydrophilic interaction liquid chromatography; LC, liquid chromatography; MS, mass spectrometry; MWA, metabolome-wide association; NMR, nuclear magnetic resonance; OPLS-DA, orthogonal partial least squared-discriminant analysis; PC, principal component; PCA, principal components analysis; Q-TOF, quadrupole coupled with time-of-flight; RF, radio frequency; RP, reversed-phase; UPLC, ultra-performance liquid chromatography; VIP, variable importance of projection; mass spectroscopy; mass-charge ratio; metabolic profiling; metabolomics; targeted profiling.