GS-IR machines....I used them plenty in my time as an analytical chemist.
The UV-VIS-IR stuff is not as bad as you may think!
A diffraction grating that is moved through an axis to get different wavelengths of light filtered.
Your detector can then read the individual wavelengths and produce a "graph"/Spectrum of the sample.
You can feed the output of your GC along a sample glass tube. This gives a "live" full spectrum analysis of what you have separated.
The first peak is your usual carrier gas, then you can time the following peaks as they come off to give retention times. Having the IR/UV/VIS spec gives a better analysis as you can identify multiple chemicals in one sample.