Introduction 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

Early Gas Chromatography Detectors The first GC detector was invented by James and Martin [4] in 1952, and used for the separation of some fatty acids. It consisted of a titration apparatus situated at the end of the column and the eluent gas was bubbled through a suitable aqueous liquid to absorb the solutes. The solution contained an indicator and, as each solute was eluted, the solution was manually titrated. The titration process was eventually automated and an integral chromatogram was obtained by plotting the volume of base solution added against time. The integram

chromatography for this type of separation (color writing). Although color has little to do with modern chromatography, the name has persisted and, despite its irrelevance, is still used for all separation techniques that employs the essential requisites for a chromatographic separation,viz. a mobile phase and a stationary phase. The technique, as described by Tswett was largely ignored for a along time and it was not until the late 1930s and early 1940s that Martin and Synge(2) introduced liquid-liquid chromatography by supporting the stationary phase, in this case water, on silica in a packed bed and used it to separate some acetyl amino acids. In their paper, they recommended replacing the liquid mobile phase by a suitable gas, as the transfer of sample between the two phases would be faster, and thus provide more efficient separations. In this manner, the concept of gas chromatography was created but again, little notice was taken of

References   1. A. S. Said,  Am. Inst. Chem. Eng. J., 2(1956)477.   2. A. J. P. Martin and R. L. M. Synge, Biochem. J., 35(1941)1358  3. A. T. James and A. J. P. Martin, Biochem. J., 50(1952)579.  4. 4. H. Engelhardt, H. Muller and B. Dreyer, Chromatographia,       19(1984)240.   5. P. L. Zhu, Chromatographia, 20(1985)425.   6. J. H. Knox and R. J. Kaliszan,  J.  Chromatogr., 349(1985)211.   7. R. J. Smith and C. S. Nieass,  J. Liq. Chromatogr., 9(1986)1387.   8. R. P. W. Scott and P. Kucera

of volatile compounds have been of great commercial interest to all civilizations for thousands of years. Originally the most important were the essential oils extracted from various plants and subsequently used as perfumes, food flavorings, and for medicinal purposes. Later, with the advent of the industrial revolution, petroleum fractions, solvents and coal products, such as coal tar and benzole mixtures were added to the list. Prior to the introduction of gas chromatography (GC) by James and Martin (1) in the early 1950s, the analysis of complex mixtures of volatile substances was extremely difficult and time consuming to carry out.   At that time, the only effective procedure for separating and analyzing such materials was by distillation using (what was then) high efficiency fractionating columns which, due to their very long equilibrium times, many days (sometimes weeks) were necessary to complete a separation. In addition, the distillation process was only really effective

to the condemnation of the method by Willstatter and Stoll (2) in 1913. Willstatter and Stoll repeated Tswett's experiments without heeding his warning not to use too "aggressive " adsorbents as these would cause the chlorophylls to decompose. As a consequence, the experiments of Willstatter et al. failed and their published results, rejecting the work of Tswett, impeded the recognition of chromatography as a useful separation technique for nearly 20 years. In the late 1930s and early 1940s Martin and Synge introduced a form of liquid-liquid chromatography by supporting the stationary phase, in this case water, on silica gel in the form of a packed bed and used it to separate some acetyl amino acids. They published their work in 1941 (3) and in their paper recommended the replacement of the liquid mobile phase with a suitable gas which would accelerate the transfer between the two phases and provide more efficient separations. Thus, the concept of gas chromatography was born. In