Chromatography Forum

hello
Thanx Rod
I able to resolve peaks of ethanol and water separately . Now I have another one.
I want to analyse mixture of ethanol, water, acetone, butanol and 2-ethyl1-hexanol in GC using PorapakQ column. resolution of ethanol, water, acetone and butanol was ok but 2-ethyl1-hexanol did not.
I tried several times.
I cant understand wht type of column condition I have to put.
Can anybody help me?
Happy New Yr

As you discovered, molecules larger than C7 elute quite late and with broad widths, especially the branched chains like ethyl hexanol. I would expect you would be required to go to 250C for several minutes to elute 2EtC6ol

Look at the web sites of Restek, Supelco, Alltech, and others to see which capillary column might work for your mixture.

If you can find McRenyolds book, it might save you a lot of searching for a packed column selection.

I suspect a MS capillary might work but I don't have time today to do a search for you so please look on the web for your answer.

best wishes,

Rod

I'd think a polar ("Wax") column would do it, but you'd have to try it out and look at the separation. I'm surprised that the "Q" column works, our experience with that column is for permanent gases and any moisture just kills the separation.

FYI

I used Q columns for years for solvent determinations, from dioxane to methanol. Separations are poor if the column is packed poorly which has been known to happen.

USP some years ago had acetonitrile as an ISTD for ethanol determinations. This separation is possible but difficult if the column is poorly packed.

Overloading the column with more than 1 microliter of water can affect separations.

I used to have 'grams of many solvents in 1 chromatogram using the Q column.

But they were never scanned into jpegs to share on line.

best wishes,

Rod