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The Basic Column Chromatograph A chromatograph consists of five basic units and these units, although possibly designed differently for different systems, are essential for all types of chromatograph, including both gas and liquid chromatographs. The layout of all the five essential units is shown in figure 24. They consists of a mobile phase supply, a sampling system, a column and column oven including a temperature controller and temperature programming system. The temperature controller and

The Basic Liquid Chromatograph The basic liquid chromatograph consists of six basic units. The mobile phase supply system, the pump and programmer, the sample valve, the column, the detector and finally a means of presenting and processing the results. A block diagram of the basic liquid chromatograph is shown in figure 1 Figure 1. The Basic Liquid Chromatograph

majority of the added devices and techniques were suggested or describe in the first three international symposia on gas chromatography held in 1956, 1958 and 1960. These symposia, initially organized by the 'British Institute of Petroleum' have been held every two years ever since 1956 and the meetings have remained the major stimulus for developing the technique and extending its capabilities. However, the majority of the techniques and devices that have been incorporated in the modern chromatograph, were described, reported, or discussed in the first triad of symposia.   The layout of the modern gas chromatograph is shown as a block diagram in figure 1.  

Apparatus for use with Capillary Columns   The apparatus used specifically with capillary columns differs very little from the general gas chromatograph. Capillary columns require particular sampling systems and also have a more restricted range of suitable detectors than those usable with packed columns, but other than that, the capillary gas chromatograph is identical to that used with packed columns. A diagram of the lay out of a gas chromatograph used specifically with capillary columns is shown in figure 5.   Gas Supply   The gas supply incudes the usual gas tank, reducing valve and flow controller; the pressures

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

which is also perceived by some as a serious fire hazard despite the fact that they have been used in laboratories, quite safely for nearly a century. Supplies from Gas Tanks Gasses are stored in large cylindrical tanks fitted with reducing valves that are set to supply the gas to the instrument at the recommended pressure defined by the manufacturers. The cylinders are often situated outside and away from the chromatograph for safety purposes and the gasses are passed to the chromatograph through copper or stainless steel conduits at relatively low pressure. The main disadvantage of gas tanks is their size and weight which makes them difficult to move and replace.   Pure Air Generators. Air generators require an air supply from air tanks or directly from the laboratory compressed air supply. The Packard Zero Air Generator passes the gas through a 0.5 m filter to remove oil and water and finally over a catalyst to remove hydrocarbons. The