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GC-MS

GC is probably the highest-resolution form of one-dimensional chromatography; and it has a venerable history. Providing a second dimension of separation by combining GC with MS produces a superb method GC/MSfor screening for large numbers of chemicals in a complex mixture.

This is an easy combination to make. A mass spectrometer detector must operate under a near vacuum. Otherwise ions would colide with molecules from the air. It is not difficult to pump away the carrier gas at the end of the GC column, and create a suitable vacuum, in which the eluting metabolites can then be ionized.

Ionization is usually by electron beam, or exposure to ions of an ionization gas, itself ionized by an electron beam. These processes, particularly direct electron ionization, yield very different spectra to those typical of LC-MS. More details are available about contrasts between LC-MS and GC-MS data.

The one disadvantage of GC is that the sample must be volatile, since it will be separated in the gas phase. This usually means that biological samples need to be derivatised.

The John Innes Centre posesses an Agilent GC-MS 6890N with a 5973 inert MSD