J Mass Spectrom Adv Clin Lab. 2022 Jan;23
7-13
Ion mobility spectrometry (IMS) is an analytical technique where ions are separated in the gas phase based on their mobility through a buffer gas in the presence of an electric field. An ion passing through an IMS device has a characteristic collisional cross section (CCS) value that depends on the buffer gas used. IMS can be coupled with mass spectrometry (MS), which characterizes an ion based on a mass-to-charge ratio (m/z), to increase analytical specificity and provide further physicochemical information. In particular, IMS-MS is of ever-increasing interest for the analysis of lipids, which can be problematic to accurately identify and quantify in bodily fluids by liquid chromatography (LC) with MS alone due to the presence of isomers, isobars, and structurally similar analogs. IMS provides an additional layer of separation when combined with front-end LC approaches, thereby, enhancing peak capacity and analytical specificity. CCS (and also ion mobility drift time) can be plotted against m/z ion intensity and/or LC retention time in order to generate in-depth molecular profiles of a sample. Utilization of IMS-MS for routine clinical laboratory testing remains relatively unexplored, but areas do exist for potential implementation. A brief update is provided here on lipid analysis using IMS-MS with a perspective on some applications in the clinical laboratory.
Keywords: CCS, collisional cross section; CV, compensation voltage; CVD, cardiovascular disease; Clinical analysis; DG, diacylglycerol; DMS, differential mobility spectrometry; DTIMS, drift tube ion mobility spectrometry; EV, elution voltage; FAIMS, field asymmetric waveform ion mobility spectrometry; FIA, flow injection analysis; FTICR, fourier-transform ion cyclotron resonance; HDL, high-density-lipoprotein; HRMS, high-resolution mass spectrometry; IMS, ion mobility spectrometry; IMS-MS, ion mobility spectrometry-mass spectrometry; Ion mobility spectrometry; LC, liquid chromatography; LDL, low-density-lipoprotein; LPC, lysophosphatidylcholine; Lipids; MALDI, matrix-assisted laser desorption/ionization; MS, mass spectrometry; Mass spectrometry; NBS, newborn screening; PC, glycerophosphocholine; PE, phosphatidylethanolamine; PG, phosphatidylglycerol; RF, radio frequency; SLIM, structures for loss less ion manipulations; SM, sphingomyelin; SV, separation voltage; TG, triglyceride; TIMS, trapped ion mobility spectrometry; TOF, time-of-flight; TWIMS, traveling wave ion mobility spectrometry; VLDL, very-low-density lipoprotein; m/z, mass-to-charge ratio