Chromatographic couplings with mass spectrometry. II

Gas chromatography-mass spectrometry (GC-MS) is the first successful combination of a chromatographic method and mass spectrometry. Developed in the late 1950s, it has been regularly marketed since 1966. This coupling has been fully mastered since 1980, and the explosion of benchtop instruments in 1990 testifies to the universality and sensitivity of the mass spectrometer as a chromatographic detector. These instruments can be found in most organic analysis laboratories, as they have become more compact and less expensive. Being totally computer-controlled, GC-MS coupling is simple to implement, and several instruments can operate simultaneously under the supervision of a single manager.

The field of application for GC-MS overlaps with that of GC, and all recent advances in GC have been transposed to GC-MS, particularly in terms of analysis speed, thanks to recent TOF/MS (time of flight mass spectrometer) analyzers. This field is limited only by sample volatility, and not by instrumental constraints, but it is sufficiently extensive to qualify it as universal. This universality goes hand in hand with a very high level of selectivity when it comes to searching for a particular molecule in a complex mixture.

In qualitative analysis, GC-MS routinely produces reproducible spectra, identifiable with those of a library, for injected quantities of the order of 10 ^–10 g. In quantitative analysis, accurate and precise assays are obtained with a very high response dynamic, and lower detection limits among the lowest of all chemical analysis techniques, provided that the molecules to be quantified are known and available in advance, in order to establish a calibration.

This article, which does not claim to be exhaustive, focuses on those parts of the GC-MS interface which are accessible to users and which may need to be adjusted or modified in the laboratory, depending on the GC column used. It also describes the principles of the two main modes of GC-MS use: quantitative and qualitative analysis.

GC-MS coupling is covered in all general mass spectrometry books [1][2][3][4][5][6][7] . A few books are devoted exclusively to it [8]