The Basic Gas Chromatograph

The instrumentation necessary for use in chiral gas chromatography differs little from that employed in the general use of the technique; gas supplies, sampling systems, column ovens, detectors and data acquisition equipment are all the same as that used in ordinary GC analyses. The major difference is in the design of the chiral columns and in particular the nature of the stationary phases that are employed that will provide chiral selectivity. The parts of the apparatus that are essential for normal use are shown in figure 54. The chromatograph can be considered to consist of five chromatographic units and four data processing and display units.

Figure 54. The Basic Gas Chromatograph

These units consist of, gas supplies (which provide carrier gas for the column and other gases that may be necessary, e.g. hydrogen and air or oxygen for a flame ionization detector); flow controllers (controlling gas flows to the column and, where necessary to the detector, usually under computer control); an injection device, (this will vary with the type of column employed); the column and column-oven (which will include a thermostatic controller and a temperature programmer that can change the temperature over selected ranges at chosen rates); and finally a detector and amplifier (which may be one of a number of different detectors, e.g. the flame ionization detector, the nitrogen phosphorous detector, the argon detector or the katharometer detector), Historically, the output from the detector was passed to a potentiometric recorder and the analysis was carried out by making measurements directly on the chromatogram. Although this simple procedure is still carried out to some extent, the modern gas chromatograph includes a computer that acquires the data, processes it using standard software, and then reports the results on a printer (which will usually include a real-time chromatogram).