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A gas chromatograph is an instrument used to separate mixtures. The
principle is similar to extraction, except in chromatography, one
of the phases moves and one is stationary (in simple extraction, both
phases are stationary).
A GC is also useful as a means of sample introduction into the vacuum
system of a mass spectrometer.
- The fundamental unit in separation theory is the ``theoretical
plate.'' One theoretical plate is defined as the separating power
(for a given set of substances under consideration) of one simple
- The GC in this laboratory uses capillary columns that provide many
thousand theoretical plates.
- Factors that affect the number of theoretical plates, and hence separation
ability, include carrier gas (the mobile phase), gas flow rate, the
nature of the stationary phase, the column design, the detector, injection
technique and temperature programming.
John S. Riley, DSB Scientific Consulting