Gas Chromatography - Introduction > Page 1
Chromatography, in one of its several forms, is the most commonly used procedure in contemporary chemical analysis and the first configuration of chromatography equipment to be produced in a single composite unit and made commercially available was the gas chromatograph. Gas chromatography was invented by A. J. P. Martin who, with R. L. M. Synge, suggested its possibility in a paper on liquid chromatography published in 1941 (1). Martin and Synge recommended that the liquid mobile phase used in liquid chromatography could be replaced by a suitable gas. The basis for this recommendation was that, due to much higher diffusivities of solutes in gases compared with liquids, the equilibrium processes involved in a chromatographic process (see Principles and Practice of Chromatography) would be much faster and thus, the columns much more efficient and separation times much shorter. So the concept of gas chromatography was envisioned more than fifty years ago, but unfortunately, little notice was taken of the suggestion and it was left to Martin himself and his coworker A. T. James to bring the concept to practical reality some years later in 1951, when they published their epic paper describing the first gas chromatograph (2).
The first published gas chromatographic separation was that of a series of fatty acids, a titration procedure being used, in conjunction with a micro burette, as the detector. The micro burette was eventually automated providing a very effective in-line detector with an integral response. After its introduction by James and Martin, the technique of GC developed at a phenomenal rate, growing from a simple research novelty to a highly sophisticated instrument, having a multi-million dollar market, in only 4 years. The gas chromatograph was also one of the first analytical instruments to be associated with a computer which controlled the analysis, processed the data and reported the results.
A more sophisticated form of the gas chromatograph was constructed by James and Martin and described by James in 1955 (3). The instrument was a somewhat bulky device with a straight packed column, 3 ft long, that was held vertically and thermostatted in a vapor jacket. Initially, the detector was situated at the base of the column and consisted of the automatic titrating device, the separation was presented as a chromatogram in the form of a series of steps, the height of each step being proportional to the mass of solute eluted. The apparatus was successfully used to separate some fatty acids, but the limited capability of the device to sense only ionic material motivated Martin to develop a more versatile detector, the Gas Density Balance.