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Does Water Show Up In Gas Chromatography?

May 5, 2022

So let me answer this a couple different ways. First of all, in a GC our predominant detector, our main detector is the FID, flame ionization detector.

The FID cannot see water. Water does not have any carbon hydrogen bonds so therefore the FID has no ability to see it. 

In the GC world we have one main detector, the FID and we probably have a dozen specialty detectors. So if you want to measure water then you would have to use a TCD, thermal conductivity detector. TCD is universal and can detect any molecule in the world. 

I’ll warn you about this one though water does not have a good peak shape. Water is very, very polar. Obviously it does a lot of hydrogen bonding so it tends to give poor peaks, broad peaks, tailing peaks but it can be done by GC. We could run water but we need something other than an FID. We need a thermal conductivity detector. 

One other comment I’ll make is that water has a cooling effect on the FID so even though we cannot see water with the FID, it does tend to cool off the jet. It gives us a little bit of noise when that happens. If you’re injecting large amounts of water and you have peaks that come off really early, sometimes we worry about good reproducibility in peak areas and that comes up with early peaks because of that cooling effect of the water. In my experience, I have not found that to be a big deal. I think the cooling effect is fairly minor. It is there but it’s a fairly minor effect. 

If you want to see water get a thermal conductivity detector and that will actually allow you to visualize it so it is possible to do water by gas chromatography. A better way to do it is just to do titrations. There’s an easy approach out there that is used by most people so I would probably avoid the GC and probably just go to titrations in order to measure it.

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