Acetic acid and wax columns

[Andy F]

Hi hope you can help,
Currently we are analysing alcoholic beverages for ethanol and other flavour volatiles by direct injection and headspace respectively. The methods have been in place for years and are sufficiently robust for our needs.

We have now been asked to do the same analyses, but on an approximately 5% acetic acid solutions and I'm a bit worried that the acid might damage the columns. The columns involved are HP Innowax for the direct injection and CP Wax 57 CB and SGE BP20 for the headspace applications.

May thanks for your help

Andy

[MSCHemist]

Acetic acid won't damage the column. It is pretty common to use wax column or other high polar columns for free fatty acids.

[turangul]

I am using CP Wax 57 CB column (25m 0.53 mm 0.5 µm film thickness) in direct injection mode to analyse ethylene glycol propeylene glycol and acetic acid. I use splitless double taper ultra inert GC-liner (800 µL) (agilent 5190-3983). Ethylene glycol and propylene glycol peaks are quite stable but only Acetic acid peak is shifting to a later retention time after 5 injections of 40 ppm concentrations of those compounds as a standard mixture. Is this a common problem with this column? Do you also experience this in your analysis? The diluent is water. I would appreciate if you can share your experience.

[MSCHemist]

I don't inject water except via headspace. I see acetic acid frequently on the wax coln and it seems to have a stable retention time. If you have to inject water I'd use a guard column and replace it and the liner frequently. I do propylene and other glycols by derivatizaing by phenylboronic acid. PBA in acetone added to aqueous sample 90 deg C for 30 minutes cool and salt out into hexanes.