Mass spectrometry

Abstract

Mass spectrometry is a powerful technique for the identification of pure compounds. It can also be used for confirmation of the purity of a sample and for quantitative analysis of mixtures. Ions are produced from sample molecules by various methods, including bombardment with a beam of electrons, and they are then accelerated and separated from ions of different molecular mass prior to detection. Often, the molecular or parent ion, which is produced from the sample molecule by loss of an electron, is observed together with a large number of ions (daughter ions) produced by characteristic fragmentations of the molecular ion. The molecular ion gives the relative molecular mass of the compound directly, while the fragmentation pattern provides a fingerprint which is used for identification of the molecule. The mass spectrum consists of a series of peaks of varying intensity plotted against the mass-to-charge ratio (m/z). Mass spectrometry combines high specificity with great sensitivity, since amounts of less than a picogram of some compounds can be detected.