Ion Mobility Spectrometry in Forensic Science

Abstract

AbstractThe ion mobility spectrometer (IMS) is a device used primarily for detection, identification, and monitoring of trace amounts of gases or vapors. Generally, sample introduction, ionization, ion separation, and detection all take place at ambient pressure, so that elaborate vacuum systems are not required. IMSs are typically small (portable, hand‐held or even pocket‐sized) and respond within seconds to part per billion (ppb), or even part per trillion (ppt) concentration levels. The IMS is not a universal detector and is not suitable for all compounds. It has a limited dynamic range due to its finite reservoir of charge, and may suffer from matrix effects which could interfere with the ionization or ion separation processes and cause spectral interferences. These drawbacks have limited the application of IMS technology to a few fields that require high sensitivity and rapid response, such as the detection of chemical warfare agents (CWA), explosives, and illicit drugs, and the identification and monitoring of toxic gases or vapors.The array of field and laboratory instruments available today have become useful tools in the prevention of illicit use of contraband substances and in the rapid identification of these and other toxic substances. This article describes the principle of operation of IMSs and the basic gas‐phase ion chemistry underlying the technology. The proven experience, both in the field and in the laboratory, of IMSs for forensic science applications is also described, and the merits and shortcomings of present‐day IMS technology, and future trends, are discussed.