Mass Spectrometry

Abstract

Mass spectrometry (MS) is the most widely used identification technique in forensic toxicology. In a mass spectrometry, the sample, usually following chromatographic separation, enters the mass spectrometer through an inlet device. Once inside the ion source, the sample components are ionized and selectively monitored by the mass analyzer. The ions that exit the mass analyzer enter the instrument’s detector. Common ionization techniques for gas chromatography-MS are the electron ionization, where significant fragmentation can occur, and the softer chemical ionization. Common liquid chromatography-MS ionization techniques are electrospray ionization, atmospheric pressure chemical ionization, and collision-induced dissociation. The quadrupole, ion trap, and time of flight are common mass analyzers. Currently, multistage mass spectrometers have gained widespread use. Although an identification technique, MS coupled with its hyphenated chromatographic techniques is widely used in quantitative analysis as well.

Mass spectrometry (MS) was developed about 80 years ago and has since been applied in a wide variety of scientific disciplines. The applications of MS run the gamut from the elucidation of fundamental physical and chemical properties of substances to the study of large biological molecules. The technique has come into widespread use in the last several decades, largely because of the development of small, relatively inexpensive instruments that are easy to operate. Advances in computers and sophisticated software have reduced the need for training, because instruments can be controlled and data acquired with little analyst intervention. Moreover, various advances have made MS technology more usable for a wider variety of compounds in a diverse array of scientific endeavors, most recently in elucidating the nature of the genome and its encoded protein products. Since the previous edition of this book, the use of MS in forensic toxicology has begun to transition toward more applications that use liquid chromatography (LC), tandem MS (MS/MS), and time-of-flight (TOF) MS. The introduction of these techniques into forensic analysis promises to be an exciting area of advancement in the coming years.