Chromatography Forum

Now I am analyzing VFA ( Acetic, Propionic and Butyric Acid) by GC and to clean auto injector I am using ethanol. If I want to detect ethanol along with VFA, what solvent should I use.
Thank you

Have you any candidates ?

I'd use methanol.

What is your sample injection solvent?

I agree methanol would be ideal. Acetone would be a good one as well. Also acetonitrile would work. If your samples are in water you want to have a water soluble cleaning solvent.

I would wash with methanol then DI Water to remove as much methanol as possible to avoid any carryover peaks in the injection that might give problems with Ethanol. Just depends on how much separation you get between methanol and ethanol. If doing water injections you should not have a problem using water as a rinse or at least a second rinse.

This brings to mind this side topic. In the mid-1990s, we found that a contract lab in Texas working for our potential contract manufacturer was using HPLC grade ethanol as the ethanol standard for GC, believing that to be the highest grade. They failed to see that their ethanol was really only about 90% ethanol, also had 5% methanol and 5% isopropyl alcohol in it as denaturants.

So one should source 99+% ethanol to use as standard.

Or just use rectified spirits (96%) and do a Karl Fischer to ensure the water content (should be 4%) in order to get the purity.

At least if you don't need USP level precision/accuracy. You should probably test the absolute EtOH anyways as it can absorb moisture.

Thank you all for your suggestions.