Recent developments in mass spectrometry for the analysis of complex mixtures.

Abstract

Analytical chemists faced with complex problems such as food or drug analysis, chemical dump site analysis, or incorporation of xenobiotics and natural toxins into the food chain, require increasingly sophisticated analytical tools. Recent developments in mass spectrometry may be applied to some of these analytical problems. Negative chemical ionization mass spectrometry and to a lesser extent tandem mass spectrometry have passed the stage of expensive curiosities and are now vital screening tools. Negative chemical ionization is a powerful new method for the analysis of complex environmental samples for trace levels of both oxidizing and alkylating agents. Since these compounds comprise a large number of substances known to cause cancer or other environmental health problems, it seems likely that use of NCIMS will continue to grow. Tandem mass spectrometry has several advantages for the analysis of specific organic compounds in complex mixtures. Target compounds can be isolated and identified almost instantaneously at detection limits comparable and identified almost instantaneously at detection limits comparable to GC-MS with minimum sample preparation. A major deterrent to MS/MS is price ($400,000 or more). Also, the operator must know something about the sample and what to look for. Complete characterization of a sample by MS/MS is impractical. In the past, application of mass spectrometry to the determination of molecular weight and structure of polar (or thermally labile) compounds was severely limited. The limitations are due to inability to vaporize samples or to prevent thermal decomposition. The development of desorption chemical ionization, fast atom bombardment, secondary ionization mass spectrometry, and 252Cf plasma desorption mass spectrometry was in an attempt to rectify this situation. Each of the ionization techniques has advantages and limitations. With continued research into actual ionization/desorption process and continued instrumentation development (perhaps with a lower price tag), many of these techniques will become commonplace.