The Mass Spectrometer and Its Components

Abstract

Mass spectrometer measures mass-to-charge ratio (m/z) of gas-phase ions. It has three main components: ion source, mass analyzer, and detector. Ion source converts analyte molecule into gas-phase ions, a mass analyzer separates ionized analyte according to their m/z, and a detector records number of ions at each m/z value. The advent of electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) transformed the field of proteomics. Several types of mass analyzers are used nowadays: quadrupole, ion trap, time-of-flight, and Orbitrap. Detector and vacuum system are also an integral part of the mass spectrometer. Tandem mass spectrometry (MS/MS) utilizes two stages of mass analysis to examine selectively the dissociation of specific ion(s) using various fragmentation techniques including collision-induced dissociation (CID), which is used exclusively for selected reaction monitoring-mass spectrometry (SRM-MS).