Interactive numerical educational resources for the analysis of complex media
Gas chromatography detection
The chromatographic column is located inside an oven
It is composed of a narrow tube
with a very small internal diameter
around 0.32 mm
The carrier gas flows inside this tube
and drives the volatile constituents of the sample
which will be separated
The chromatographic oven
allows to warm the volatile components
Generally, the temperature
goes from the room temperature
around 40Â°C
to a relatively high temperature
around 250-300Â°C
which allows to volatilise
the components with a high boiling point
for them to be driven by the carrier gas
The separation along the chromatographic column
is due to two different effects
The interaction with the stationary phase
The relative volatilisation of a component compared to the others
so almost their boiling point
The separated components will then enter in the detector
at the end of the column
The flame ionization detector
is a universal detector often used in gas chromatography
in reason of its high sensitivity
and its capacity to detect all the organic compounds
This detector
will produce a signal proportional to the quantity of component
which goes through the detection cell
In the recording of this signal
called chromatogram
the components are represented
by the chromatographic peaks
The surface of these peaks
allows to know the quantity of each component
in the injected sample
As you can learn in this website
there are different techniques for the calibration
external or internal
For gas chromatography
in reason of the poor repeatability of the injections
technique of internal calibration is preferred
If a more informative detector
as the mass spectrometer is used as a detector
it is then possible to obtain the spectrum
of the different components of the analysed solution
For example, here
if I click on a chromatographic peak
which represents a component
I will get the mass spectrum of the component
It is then possible to identify its related compound
by looking in the spectrum library
for the spectrum which is closest to the spectrum I got
Thanks to that
it is possible to know all the components of a solution
as well as their quantity
It is then possible to know the complete composition of a solution
Gas chromatography detection
Interactive numerical educational resources for the analysis of complex media