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Chapter 5
Glossary
analyte
carrier gas
Any chemical component to be analyzed. Internal standards, external
standards, target components, quality control samples, knowns, and
unknowns can all be considered analytes
The mobile phase in gas chromatography. The carrier gas carries the
analyte mixture through the GC column, where it is separated into its
individual components. The carrier gas flows through the GC column at a
specific rate, measured either as a linear velocity (cm/sec) or as a flow
rate (mL/min). Common carrier gases are helium, hydrogen, and nitrogen.
Hydrogen offers the best chromatographic properties (optimum resolution
at the highest flow rates). However, because hydrogen is flammable,
helium is often used as a safer alternative for a carrier gas.
See also: chromatography, constant flow, linear velocity, flow rate, and
resolution
chromatography
A process in which a chemical mixture carried by mobile phase (gas or
liquid) is separated into its individual components as a result of
differential distribution of the analytes as they flow around or over a
stationary phase (liquid or solid).
See also: liquid chromatography and gas chromatography.
column flow
The flow of mobile phase of carrier gas through the chromatographic
column. Column flow is usually reported as a linear velocity (cm/sec) or
as a flow rate (mL/min).
See also: linear velocity and flow rate.
constant flow
The type of flow control available on gas chromatographs to regulate the
flow of carrier gas through the GC column.
Flow rates are specified in units of mL/min.
In the Constant Flow mode, the flow rate of the carrier gas is maintained
at a designated setting for the duration of the GC run. The head pressure
of the carrier gas in the injector is electronically adjusted during the oven
temperature program to compensate for changes in the gas viscosity and
thereby maintain the desired flow rate.
data system
The computer hardware and software used to control the instrument and
to record, analyze, and interpret the data collected by the instrument.
_______________________________ TRACE Gas Chromatograph Setup User’s Manua ________________
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