analysis of ethanol

[Shashikiran]

please could anyone be kind enough to provide a protocol for analysis of ethanol from wine..i have a gc (thermo scientific)with db1 and db 5 column with fid detector...also i have a hplc(dionex) with c18 column with uv detector...

[DSP007]

Siloxanes not good, need FFAP or WAX

[Shashikiran]

Siloxanes not good, need FFAP or WAX

I am sorry but i couldnt follow you..could you be more precise..

[Peter Apps]

What DSP is trying to say is that the columns that you have, with their siloxane phases, are not suitable for the analysis of ethanol content, and that you need a wax type (polyethylene glycol) or FFAP phase column.

These are available from all the column manufacturers.

How best to determine the ethanol content of wine depends on how many samples you need to run, how accurate the results have to be, and what other equipment besides the GC you have available.

I would recommend that you (and the numerous other posters who want a method off the shelf from this forum) do a search, either on the internet as a whole or in the scientific literature, for routine methods with a proven track record. Having thus shown that you are prepared to invest some of your own time and effort, you will find that useful answers are more forthcoming from the forum.

Peter

[Consumer Products Guy]

If you need a test procedure for regulatory reasons, I'd say to use USP <611>. This uses a sample diluted with water to about 2% ethanol, and uses acetonitrile (yes) as internal standard on a "624" type capillary.

In reality, chromatography of the ethanol peak is "OK" on a "624" type capillary, but not great (tailing factor runs about 1.5). Better chromatography exists with same preparation on a PEG (wax) capillary, and n-propyl alcohol makes for a darn good internal standard as well.

[Shashikiran]

What DSP is trying to say is that the columns that you have, with their siloxane phases, are not suitable for the analysis of ethanol content, and that you need a wax type (polyethylene glycol) or FFAP phase column.

These are available from all the column manufacturers.

How best to determine the ethanol content of wine depends on how many samples you need to run, how accurate the results have to be, and what other equipment besides the GC you have available.

I would recommend that you (and the numerous other posters who want a method off the shelf from this forum) do a search, either on the internet as a whole or in the scientific literature, for routine methods with a proven track record. Having thus shown that you are prepared to invest some of your own time and effort, you will find that useful answers are more forthcoming from the forum.

Peter

thanks a lot peter. ill try to keep that in my mind

[Shashikiran]

If you need a test procedure for regulatory reasons, I'd say to use USP <611>. This uses a sample diluted with water to about 2% ethanol, and uses acetonitrile (yes) as internal standard on a "624" type capillary.

In reality, chromatography of the ethanol peak is "OK" on a "624" type capillary, but not great (tailing factor runs about 1.5). Better chromatography exists with same preparation on a PEG (wax) capillary, and n-propyl alcohol makes for a darn good internal standard as well.

thank you..ill give it a try...

[gvportari]

Maybe help you:
http://labmed.ascpjournals.org/content/39/1/42.abstract

Validation of a Manual Headspace Gas Chromatography Method for Determining Volatile Compounds in Biological Fluids. (2008) LabMedicine, 39, 42-45.

We have also used for determination of ethanol in aqueous matrices (eg, coffee):

http://www.akademiai.com/content/b4366p ... 4dc45&pi=4

Effect of the temperature and pH on methanol release in coffee brew sweetened with aspartame. Acta Alimentaria. Volume 38, Number 3/September 2009.

[WillyOne]

Ethanol in wines is not a Chromatographic method.
250 ml of wines are distilled after being added a volume of an Hydroxide of Ca or Mg to avoid the codistillation of volatil acides, to a distilled volume of 150 ml or something like that. then the distillate is added wiht water to a volume of 250 ml in a calibrated flask. After homogeneization the specific mass 20°C is determined in an electronic densimeter accurate to 0.00001. The alcohol content is calculated from tables introducing the density value

[chromatographer1]

If you want to measure the amount of IPA in ethanol then you need the capillary 624 column or a packed Q polymer column. Acetonitrile and ethanol can be separated on a packed Q but it has to be packed with a minimum amount of voids. This may or may not be available from vendors.

LC of course is not suited for ethanol analysis.

Acetaldehyde and ethyl acetate, isopropyl and n-propyl alcohols, as well as methanol are obvious possible contaminants for ethanol. IPA and EtOH barely separate on a capillary or packed Wax column.

best wishes,

Rod

[Consumer Products Guy]

Tenax-GC in a packed column will also separate ethanol and IPA.

[chromatographer1]

Almost any of the porous polymer packings (Hayesep, Porapak, Century series) will separate ethanol and isopropanol.

Rod

[Karen01]

LC of course is not suited for ethanol analysis.

It certainly can be easily done by LC using an Aminex HPX-87C column and and RI detector down to about 1 g/L ... Though GC can be a lot faster and certainly a lot more sensitive.

- Karen

[chromatographer1]

Karen,

Thanks for the info. I always like to learn new (for me) things.

Do the possible impurities like acetaldehyde, methanol and IPA separate well?

How low a measurement can be made with these?

Thanks,

Rod

[Karen01]

I was using it for sugars and ethanol (the 87H would be good for HOAc too IIRC).

I did inject IPA and got a nice peak but I don't recall if something interfered. I believed all you mentioned are retained, but I could not swear to it

As for amounts... well RI is NOT very sensitive... for what I was doing al I ever needed was down to 1 g/L and that was achievable.

These days I do ethanol, acetaldehyde, methanol, IPA as well as some others by a fast Isothermal GC method.

- Karen