GC is a chromatographic technique of separation in which the gas
(e.g. Nitrogen, Helium) used as a mobile phase. Gas chromatography is one of
the most accepted techniques for separating and analyzing analytes, because of
its high accuracy, reproducibility, resolution, speed, and low range of
detection. GC can be useful for the separation of any volatile compound, hence
it GC useful in the separation of many organic and inorganic compounds.
The factors that affect the resolution in the
GC is mentioned here.
The temperature of the column:
The extremely high temperature of the column is the result in
low RT and poor separation of the analytes, as all components are mainly in the
gas phase. However, the analytes require interaction with the stationary phase
to be separated.
Vapor pressure
The compounds boiling point is often associated with its
polarity. If the boiling point of the compound is low, the higher the vapor
pressure and the retention time are shorter since the compound will use more
time in the gas phase.
The concentration and volume of the sample
solution:
Generally, the peaks have an asymmetric shape. If the
concentration and the volume of the sample solution are too high, there is a
tailing in the peaks, which is the reason for poor separation. The detectors
used in the GC are extremely sensitive and they don’t need much material to
give a detectable signal. E.g. Flame Ionization Detector (FID), Mass
Spectrometer (MS), Electrolytic Conductivity Detector (ELCD), Flame Photometric
Detector (FPD), Photoionization Detector (PID) etc.
The flow rate of carrier gas:
A higher flow rate shortens the retention time, but a poor
the separation will also be observed. Since the molecules have little or no time
to interact with the stationary phase and are simply pushed through the column
by the carrier gas.
The polarity of the stationary phase on the
column and polarity of components:
If the polarity of the compound and the stationary phase are the
same, the component's RT will increase since the strong interaction with the
stationary phase. As a result, polar molecules have a longer retention time
when using a polar stationary phase and shorter retention times when using
non-polar polar stationary phase.
The length of the column used:
If you use a longer length of the column, then the retention
time of the component will increase in proportion to the column length and a
significant peak broadening will be seen. Generally, separation improves when
long columns are used in the analysis.
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