Chromatography Forum

Hi all,
We are analyzing some residues in ethanol by GC with DB-FFAP column. It seems the IPA peak is under the ethanol. Anyone could help what kind of column I should use for this analysis.
Thanks for any inputs.

Whilst not the column of choice it is possible to separate IPA and Ethanol on most columns provided the column is long enough , the capacity great enough (film thickness) and the temperature low enough.
More info. required

You appear to be looking for an IPA impurity in an ocean of EtOH. I remember years ago trying to use IPA and an internal standard for determination of EtOH in beer and I struggled with the separation on a DB-Wax. You might switch to some thing like the Rtx-5 Alcohols column or the Rtx-BAC Plus 1:

http://www.restek.com/chromatogram/view ... %7C64-17-5

As CE said, the thickest film you can get would be advisable.

I made a sample where I put 1 drop of IPA (about 15 mg) in 4 mL of EtOH. I shot it on my GC-FID that has a Rtx-5 (30 m x 0.53 mm x 3.0 µm) and I was able to separate them with pretty good peak shapes. I was using about 20:1 split.

Thanks for your help. I may have to change to the Rtx column.

I would suggest a 1301 or 1701 column for an excellent separation.

Any column with a boiling point mechanism of separation will work.

best wishes,

Rod

That is an excellent idea Rod. I forgot about that phase. The 1701 is a very good column and I bet it would do the trick.

I use a 624 to separate, MeOH, EtOH, Acetone, ACN, and DMSO, IPA comes out between Acetone and ACN