Mass Spectrometry

Mass spectrometry (MS) is a powerful analytical technique that can solve most complex problems faced by the food analytical chemist, both in a qualitative and in a quantitative manner. Since the qualitative and quantitative aspects of MSs are so powerful, they are routinely coupled with gas chromatography (GC) or high-performance liquid chromatography (HPLC) and find growing use with static sample introduction techniques. The power of the MS technique is due to its ability to place a charge on a molecule, thereby converting it to an ion in a process called ionization. The generated ions are then separated according to their mass-to-charge ratio (m/z) by subjecting them to a combination of radio-frequency (RF) and electrostatic fields in a mass analyzer and finally detected by highly sensitive detectors. The resulting signals from the detectors are digitized and processed by software to display the information as a mass spectrum, which reveals its molecular mass and its structural composition, leading to identification. An additional stage of ion fragmentation may be included before detection to elicit structural information in a technique known as tandem MS. This chapter covers the principles of MS and the instrumentation for ionization and mass analysis, details of various techniques (GC-MS, HPLC-MS, tandem MS, and high resolution MS), and food applications of MS.