TABLE OF CONTENTS Since its introduction in 1952, the technique of gas chromatography (GC) and its younger offspring capillary (open tubular) gas chromatography has grown spectacularly. Any substance, organic or inorganic, which exhibits a vapor pressure of at least 60 torr (the column temperature may be raised to 350 C) can be eluted from a GC column. The major limitation of GC is that samples, or derivatives thereof, must be volatile at the column operating temperature.
A large percentage of gas chromatographs in use today were originally supplied as packed-column instruments; some of these have been converted for operation with open tubular columns. A number of kits are available that greatly simplify retrofitting the packed-column instruments. Before conversion of an older instrument, check whether the response of the electronics is sufficiently fast.
The basic components of a gas chromatograph are as follows:
A supply of carrier gas with attendant pressure regulator and flow controller
An injection port or valve and followed possibly by a splitter
A separation column
A detector
A thermostatically controlled oven that is also able to be programmed for various heating rates
A recorder or other readout device
Each of the principal modules is composed of several electronic and pneumatic subsystems. The inlet conducts carrier gas to the column and is also heated. The detector contains excitation and amplification circuitry. The column module is made up of the gas-chromatographic column itself and the column oven. Parts most often replaced in these subsystems...
