Why is $\ce{H2}$ used in an FID, apart from the fact its combustion does not contaminate the flame?
In other words, is the temperature of the flame important or critical? Is the stability of the temperature?
Why is $\ce{H2}$ used in an FID, apart from the fact its combustion does not contaminate the flame?
In other words, is the temperature of the flame important or critical? Is the stability of the temperature?
The key to the answer is understanding how FID works.
The hydrogen flame has a minimal flame ionisation, what is needed for the low signal baseline.
Incoming organic molecules from the HPGC column create in the flame a lot of ions and increase the flame electric conductivity.
Using alternatives causing higher ionisation would decrease FID sensitivity that is not great even at ideal conditions, compared to e.g. ECD.
Another fundamental aspect of using hydrogen in gas chromatography is the so-called van Deemter curve. The curve shows the linear velocity of the gas on the x-axis and plate heights on the y-axis. It can be shown that by using hydrogen one can obtain the best efficiency as compared to any other gas.
And of course, hydrogen is required for burning the organic molecules exiting the column. It is a clean flame (no carbon background).