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Formic Acid on an Agilent HP-5 Column?
Posted: Wed Aug 22, 2012 4:04 pm
by Incitor
One component of the samples I need to analyze is Formic acid. Can I run small amounts (~3mg/ml) of formic acid through this column without activating it?
Re: Formic Acid on an Agilent HP-5 Column?
Posted: Wed Aug 22, 2012 4:35 pm
by chromatographer1
It won't do the column any good.
Film thickness has a big bearing here.
Just how do you intend to detect formic acid with your column?
Rod
Re: Formic Acid on an Agilent HP-5 Column?
Posted: Wed Aug 22, 2012 4:37 pm
by chromatographer1
How do you intend to convert all the formic acid to a free acid form? salts will NOT work for you.
Rod
Re: Formic Acid on an Agilent HP-5 Column?
Posted: Wed Aug 22, 2012 5:37 pm
by Consumer Products Guy
I've successfully used HPLC/IC with an organic acid column and conductivity detector for formic acid assay.
Re: Formic Acid on an Agilent HP-5 Column?
Posted: Wed Aug 22, 2012 5:48 pm
by chromatographer1
The method used by CPG is MUCH PREFERRED over GC.
Unless you know what you are doing, GC is NOT recommended.
Rod
Re: Formic Acid on an Agilent HP-5 Column?
Posted: Wed Aug 22, 2012 7:33 pm
by Incitor
Ok, thanks for the advice. I figured I would just detect formic acid via FID, but it sounds like this is a moot point. The film thickness is 0.25 um, in case that makes a difference.
Any new advice with this information?
Re: Formic Acid on an Agilent HP-5 Column?
Posted: Wed Aug 22, 2012 8:00 pm
by GCMSNoob
Restek and others have some chromatograms analyzng derivitized formic acid by GC/FID or GC/MS.
Re: Formic Acid on an Agilent HP-5 Column?
Posted: Wed Aug 22, 2012 9:31 pm
by chromatographer1
You will NOT be able to detect formic acid by FID.
Sorry,
Rod
Re: Formic Acid on an Agilent HP-5 Column?
Posted: Wed Aug 22, 2012 9:44 pm
by Incitor
Ok, thanks for all your helpful advice. I think I will just stick with a liquid/liquid extraction and titration for now.
Re: Formic Acid on an Agilent HP-5 Column?
Posted: Thu Aug 23, 2012 3:30 pm
by GCMSNoob
You will NOT be able to detect formic acid by FID.
Sorry,
Rod
Not with this column, but Phenomenex has a method for detecting the methyl esther here:
http://www.phenomenex.com/Application/D ... ias=formic acid&returnURL=/Application/Search
Re: Formic Acid on an Agilent HP-5 Column?
Posted: Thu Aug 23, 2012 3:55 pm
by chromatographer1
Correct, one has to derivatize the formic acid to see it by FID. The free acid does NOT detect with a FID.
best wishes,
Rod
Re: Formic Acid on an Agilent HP-5 Column?
Posted: Fri Aug 24, 2012 12:59 pm
by Yama001
What is the issue there, Rod? Little or no FID response? Or the free acid cannot make it through the inlet/column/detector?
Thanks.
Re: Formic Acid on an Agilent HP-5 Column?
Posted: Fri Aug 24, 2012 1:43 pm
by chromatographer1
Well, there is almost no response with an FID.
But getting the acid there with a non-free acid phase is quite a difficult matter.
HID or TCD will work for detectors. But on column injection, followed by a free fatty acid phase can elute the free acid.
But not on a 5% phenyl methyl silicone phase.
best wishes,
Rod
Re: Formic Acid on an Agilent HP-5 Column?
Posted: Fri Aug 24, 2012 4:02 pm
by Incitor
Why is it that there's no response from an FID? Is it because the formic acid won't Ionize?
Re: Formic Acid on an Agilent HP-5 Column?
Posted: Fri Aug 24, 2012 5:55 pm
by chromatographer1
There are still issues with exactly HOW an FID works. I have read variations on the mechanics of the detector and I don't know if anyone has nailed it.
Be that as it may, certain gases in a hydrogen flame just don't give much or any of a response. I prefer to think that formic acid is methane that is almost completed oxidized already when in its formic acid form. Your proposal that it does not ionize is as good as any I have heard. Or if it does ionize it does not conduct electricity well in gaseous state between two electrodes.
Life is chemistry and chemistry can be a pain. Everything else is commentary.
best wishes,
Rod