Gas chromatography (GC) is a high-resolution separation techniques. It is straightforward to achieve in excess of 100,000 plates, also in routine situations. GC also has fantastic detection options, mainly because the gaseous mobile phase gives rise to little or no background. The flame-ionization detector is nearly universal, extremely sensitive, and linear across seven decades (or more). The combination of GC with mass spectrometry (MS) in GC-MS is a very strong identification tool, thanks to information rich and reproductible electron-ionization spectra.
The relatively high diffusion coefficients of analytes in gases allow the use of open tubular column, with internal diameters between 100 and 530 µm. The high permeability of such columns, in combination with the low viscosity of gases allows the use of long columns (typically 10 to 60 m). Commonly, GC analyses are not very fast, with hold-up times exceeding one minute and the duration of temperature programs often in the range of 20 to 60 min. The speed of open-tubular GC is also limited by the time it takes to cool down ovens with high heat capacities.
The main weakness of GC is that its application is limited to volatile analytes (including analytes that can be made volatile through derivatization). Another weak spot is that correct (unbiased) injection of samples is not straightforward. However, good solutions exist to address this latter issue, especially by using a programmed-temperature-vaporization (PTV) injector.
See Chapter 2 for much more information on GC.
