What is mass spectrometry?
Mass spectrometry (MS) in its simplest form is an analytical technique to measure the mass of a single chemical (and atomic) species. In more technical terms: “The basis of MS (mass spectrometry) is the production of ions that are subsequently separated or filtered according to their mass-to-charge (m/z) ratio and then detected. The resulting mass spectrum is a plot of the (relative) abundance of the produced ions as a function of the m/z ratio” Niessen, W.M.A; Van der Greef, J, Liquid chromatography – mass spectrometry: principles and applications, 1992, Marcel Dekker, Inc., New York, p.29 Mass Spectrometry is carried out in a mass spectrometer, of which there are many types. However they all have the basic modules of INLET – IONISATION SOURCE – ANALYSER – DETECTOR Generally mass spectrometers are classified by their ionisation source and analyser type. For example we are using an electrospray source (ESI), with a Time-of-Flight analyser (TOF), and therefore the instrument is known as
Coupling two stages of mass analysis (MS/MS) can be very useful in identifying compounds in complex mixtures and in determining structures of unknown substances. In product ion scanning, the most frequently used MS/MS mode, product ion spectra of ions of any chosen m/z value represented in the conventional mass spectrum are generated. From a mixture of ions in the source region or collected in an ion trap, ions of a particular m/z value are selected in the first stage of mass analysis. These “parent” or “precursor” ions are fragmented and then the product ions resulting from the fragmentation are analyzed in a second stage of mass analysis (Figure 17). If the sample is a pure compound and fragment-forming ionization is used, the product spectra obtained from the fragment ions in the normal mass spectrum can provide much additional information for structural analysis.
Numerous text books answer this question in great detail. Two classic texts are F.W. McLafferty and F. Turecek Interpretation of Mass Spectra, 4th ed. Mill Valley, CA: Univ. Science Books, 1993 and K. Biemann, Mass Spectrometry: Organic Chemical Applications, McGraw-Hill, New York, 1962. Here, however, only a few fundamental points are needed to understand how ICE works. Everything we see is composed of molecules. A pure compound consists of only one type of molecule, which is in turn composed of a combination of atoms. It is the types of atoms (elements) and the number of each in the molecule that Ion Composition Elucidation determines. Most items and environmental samples are made up of mixtures of compounds. To identify a compound using a double-focusing mass spectrometer, molecules of that compound are first ionized. The ions are manipulated by an electrostatic field and then by a magnetic field to determine the ions’ mass-to-charge ratios, which are measures of the mass of the mol
Mass spectrometry, or MS, is the measurement of molecular mass that is gained by determining the mass-to-charge ratio (m/z) of ions generated from the target molecule. Mass spectrometers are comprised of a source for generating the ions from the sample and delivering them into the gas phase; an analyzer for separating and sorting the ions; and a detector for sensing the ions as they are sorted. An MS run generates a spectrum that displays ion intensity as a function of m/z.
