Chapter 5: Combined Chromatography and Mass Spectrometry

5.1. INTRODUCTION

It is possible to collect (trap) compounds as they elute from gas or liquid chromatographic columns and afterwards to obtain their mass spectra. Such gathering of mass spectrometric data is cumbersome, especially for complex mixtures, and has been superseded by coupling the chromatograph directly to a mass spectrometer. The present chapter is concerned with the unified, continuous processes of gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS), and there will be no discussion of the trapping of chromatographic effluents prior to mass spectrometric analysis. The combinations of thin-layer chromatography, supercritical fluid chromatography and capillary electrophoresis with mass spectrometry (TLC/MS, SFC/MS and CE/MS respectively) are also considered, despite the fact that, strictly, the last of these methods is not chromatography. In purpose, though, capillary electrophoresis shares a common goal with the true chromatographic methods: the components of mixtures are separated in a flowing carrier stream prior to detection. Discussion of the chromatographic and electrophoretic processes themselves is outside the scope of this book, although general references are provided to facilitate access to this basic information (Poole and Schuette, 1984; Grob, 1985; Miller, 1988; Smith, 1988 a, 1988 b; Poole and Poole, 1991).

GC/MS is an established technique for the analysis of complex mixtures, holding a prime position in analytical chemistry because of its combination of sensitivity, wide range of applicability and versatility LC/MS instruments have not yet reached the degree of reliability that is achieved daily with GC/MS but some LC/MS devices have become established for...