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Methanol and Ethanol by headspace
Posted: Fri Sep 21, 2018 3:15 pm
by sohaib1
Hello.
I want to analyze methanol and ethanol in water by headspace GC-FID. Can you guys tell me what temperature for the incubation I will need and the syringe temperature? Also how long to agitate the vial for?
Re: Methanol and Ethanol by headspace
Posted: Fri Mar 22, 2019 2:20 pm
by MSCHemist
It depends on your sample but for ethanol I do full evaporative headspace. I put 10ul aqueous (or if it is a vegetable oil based sample I use acetone) in a 10ml tube and heat to 110 deg C for 10 minutes. I use acetonitrile as an ITSD.
Headspace is prone to matrix effects. Different samples will hold on to the analytes in the liquid phase more tightly than others so 2 samples with the same analyte amount can have different concentrations in the headspace. However, if you just vaporize everything you don't have that issue.
Re: Methanol and Ethanol by headspace
Posted: Mon Mar 25, 2019 12:56 pm
by Bigbear
If doing headspace on a water matrix, keep the incubation temp under 100C, the lower the better. We did blood ETOH,incubating at 80C.
Set your injection port to 120C, as water is not your friend.
As for agitation and incubation times you will need to run tests to determine the equilibration point. You don't need to get to full equlib point, but close to where the curve starts to flatten.