Chromatography Forum

Hello I´m Juan Manuel, I´m working in a center technology of Spain. At this moment I want to analyze Ethanol of wine by CG. I am beginning with this technique, so I am to lost.

Is it possible inject a sample of wine directly for analyze of ethanol?
What is the problem if not, the water give problems?
What is the best method?
Thank you very much.

Hi Juan

You can inject wine directly, and you may be able to separate the ethanol fom the water, but you will contaminate the GC inlet and destroy the column quite quickly. Water is a serious problem, but wine also contains significant quantities of non-volatiles.

The best GC method for ethanol in beverages is equilibrium headspace sampling. Ideally you need an automated headsapce sampler, but it can be done with a gas-tight, hand-held syringe if you are willing to sacrifice some repeatability.

Good luck Peter

Hi Juan

You can inject wine directly, and you may be able to separate the ethanol fom the water, but you will contaminate the GC inlet and destroy the column quite quickly. Water is a serious problem, but wine also contains significant quantities of non-volatiles.

The best GC method for ethanol in beverages is equilibrium headspace sampling. Ideally you need an automated headsapce sampler, but it can be done with a gas-tight, hand-held syringe if you are willing to sacrifice some repeatability.

Good luck Peter

Than you very much Peter,
I have not automated headspace, can you tell me more about it? I don´t understand system with gas-tight and I need repeatability, too.

Where is Valladolid? Is it in Spain?
Juaant - you could look at Agilent,Perkin-Elmer,Varian and Tekmar/Teledyne websites for information on headspace sampling - it would be ideal since you would eliminate unwanted non-volatiles like colours and sugar.
There are some differences between models/makes.
WK

I have routinely analyzed 100's of wines for Methanol and Ethanol in the past. We use a JW DB-624 30m x 0.53um x 3u on GC/FID. Inj 250 Det 250 Isothermal run at 40C. Inject 1ul aqueous sample. Low standard is typically 10ug/ml. This should work well with percent levels of Ethanol in wines. These alcohols typically elute in less than 5 minutes. This has been a very stable method as long as you keep up with your routine maintenance of the inj port, precolumn, and detector.

Good Luck

Vball - we also inject aqueous solutions for ethanol level on column similar to what you use, also at 40C, use n-propyl alcohol as internal standard. We use 0.5 ul injections though, because the expansion volume of water is so large.