2
StationaryPhases
VasileMatei, IulianCom
ă
nescu andAnca-FlorentinaBorcea
Petroleum andGasUniversity of Ploie
ş
ti,
Romania
1. Introduction
Gas chromatography is a physical method of separating and identifying mixtures, with
application in chemical practice, scientific investigation, petroleum technology,
environmental pollution control, the food industry, pharmacology, biology and medicine.
Separation of the sample components takes place by adsorption by a solid or by dissolving
in a non-volatile liquid, called the stationary phase. Separation takes place based on
different partitions of the sample components between a stationaryphase andmobilephase.
The mobile phase, in gaseous state, must be insoluble in the stationary phase (solid or
liquid), themobile phase continuously circulating over the stationaryphase. Separation and
measurement of components in the sample are made in a device called a gas
chromatograph. The “heart” of the device is the chromatography column. The
chromatography column contains the stationary phase, solid or liquid, as packingmaterial
for packed columns, or on the walls of capillary columns. This method of analysis has
undergone important developments in recent decades and contributed to the progress of
important scientific and applied fields.
2. Requirementsof stationaryphases
Theprincipleof gas chromatography (GC) is basedon the capacityof the stationaryphase to
produce different separation times upon exiting a chromatographic column that contains,
under one form or another, stationary phases for the various mixture components of the
sample. ThroughGC analysis, the sample components are separated through the combined
effect of the stationary andmobile phases. Themobile phase is generally a gas, such as H
2
,
He, N
2
, AR etc. The stationary phase is fixed and can produce either adsorption or
absorption. A thermodynamic equilibrium is established between the two phases; this is
expressed through the theoretic plates. When the sample components are added between
the two phases at equilibrium, a difference emerges that can be expressed as a function of
thequantities of sample components.
Chromatography is a method of separating multicomponent mixtures. This method relies
on differences in partitioning behaviour between a flowing mobile phase and a stationary
phase in order to separate the components in a mixture and on different velocities of
compounds in the mobile phase. The mobile phase is usually a permanent gas, such as
hydrogen, helium, nitrogen, argon etc., as a constant flow with a certain pressure. The
stationary phasemay be a solid or a liquid that is immobilized or adsorbed in a solid. The
