GC-SM/SM coupling

The complexity of the mixtures to be analyzed, in fields as diverse as the analysis of environmental pollutants, petroleum cuts or biological media, has led to the development of increasingly selective techniques for characterizing compounds often present in trace amounts. The advances made in these areas of analysis are mainly due to two factors:

• in the field of chromatographic separation and, in particular, gas chromatography, to the development of very high resolution capillary chromatographic columns;

• in the field of detection, to the routine development of techniques coupling chromatographic separation with mass spectrometry detection, with ever-improving qualities.

The development of tandem mass spectrometry (MS/MS) has introduced a new dimension in the analysis of complex mixtures, enabling the selection of a single ion from a matrix, which can then be dissociated to determine its structure. This technique enables the specific presence of a compound to be confirmed without any special preparation of the sample to be analyzed. However, the selectivity of tandem mass spectrometry is enhanced by chromatographic separation of the sample components. It is for this reason that the coupling of gas chromatography to tandem mass spectrometry was introduced.

The total mastery of chromatographic coupling with mass spectrometry since the early 1980s, and the development of commercial tandem mass spectrometers, has enabled the selectivity properties of these two techniques to be used to further the analytical potential expected from their combination, leaving the coupling of gas chromatography with tandem mass spectrometry (GC-MS/MS) free to assert its selectivity.

Mass spectrometric analysis of complex mixtures for particular analytes is thus facilitated by tandem mass spectrometry (MS/MS) and high-resolution/high-precision mass measurements. The value of tandem mass spectrometry is well established, for characterizing particular compounds using product ion scans, and for recognizing members of compound classes using neutral fragment losses and precursor ion scans. Collision Induced Dissociation (CID) has been studied for its ability to perform the indispensable step of activating molecular ions and generating characteristic fragments in MS/MS experiments. Accurate mass measurement, combined with sufficient resolution, makes it possible to considerably restrict the number of possible molecular formulas that could correspond to a particular molecular mass.

The analysis of environmental samples often represents a challenging task for analytical chemistry. Target compounds are usually present at trace levels in a complex cocktail...