Themes > Science > Chemistry > Organic Chemistry > Determination of Structure > Gas Chromatography Mass Spectrometry

The capabilities of integrated gas chromatography mass spectrometry are almost unique in meeting the requirements for analytical methods which are exquisitely sensitive but also specific and reliable in providing information about the biological effects of specific compounds as a function of their concentrations.

Gas chromatography is generally recognized as one of the most powerful separative methods available, and is widely employed in biomedical and environmental research. Although several selective detectors have been described, the identity of the separated components which elute must generally be inferred from their retention times relative to known standards. Mass spectrometry is a complementary technique in that it can provide a great deal of information about the identity of a compound provided that a pure sample is available, and may be sufficient to identify it rigorously. The combined system (GC/MS) can utilize both instruments to maximum advantage and, under favorable conditions can identify every major component of a complex mixture.

The GC portion of this system provides high resolution separation of volatile organic solutes in a mixture in the gas phase. As each solute exits the GC column, it is diverted into a mass spectrometer which is capable of both monitoring the amount of and identifying the chemical nature of the solute. In this way, both quantitative and qualitative information about the mixture can be obtained.

The MS portion of the system takes each gaseous solute exiting the GC and ionizes it in an electron
beam. The ions formed by a specific solute will depend on the nature of the bonds in the molecule, and
both ionized molecules and ion fragments of the molecule are possible. The ions are then directed down a separator which isolates and counts the ions according to mass. The sequence and relative intensity of the mass peaks give information about the chemical identity of the solute. The absolute intensity of the peaks provides information about the amount of substance present.

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