Chromatography Forum

hello.i want analyse methanol in wine with gc.which standart i must use?from which company you booked it?

I'd use pretty much the same method I use for ethanol Full evaporative GC-FID

I'd check the manufacturers for an ideal column. I use a 30m 0.32mm 0.5df wax column for ethanol.

I use acetonitrile as an internal standard.
I mix an appropriate amount of sample, water, and spike internal standard into a 10ml vol flask.

I put 20ul into a 20ml headspace vial.
I heat to 120 deg C
I inject 2ml 5:1 split 1.3 ml/min He column flow.

I use GC/MS SIM for ethanol but with FID I'd assume a LOQ of 50ppm methanol.

You can make your own standard out of high purity methanol and acetonitrile.

I'd probably calibrate at 50, 125, 500 and 1000 ppm.

The European Commission established a maximum admission value for methanol in spirit drinks [Regulation (EC) No 110_2008], because methanol has toxic potential. The values of methanol concentrations should be expressed in g per hectolitre of anhydrous alcohol (pure ethanol).

According to school (university) traditions volatile compounds concentration measurements in spirit drinks should be done by introducing in sample a substance of Internal Standard (IS).

It so happened that nature smiled to analysts performing analysis of alcohol production. There is the new method to determine volatile compounds in spirit products - to use “Ethanol as Internal Standard” (https://www.youtube.com/channel/UCXgL2c ... lW1oxOGqtQ ).The concentration of ethanol in alcohol drinks is always absolutely accurate and it is 789270 mg per liter of absolute alcohol (ethanol).

In the first approximation, you can determine the concentration of methanol in your wine and without constructing any calibrations. There is on-liner calculator http://inp.bsu.by/calculator/vcalc.html
Insert only two numbers from the measured chromatogram of your wine: the peak area of ethanol and the peak area of methanol.

Regards,
Siarhei

"The concentration of ethanol in alcohol drinks is always absolutely accurate and it is 789270 mg per liter of absolute alcohol (ethanol)."

Is this the concentration of ethanol in what you usually drink ? If so it would explain some otherwise puzzling phenomena.

Peter

"The concentration of ethanol in alcohol drinks is always absolutely accurate and it is 789270 mg per liter of absolute alcohol (ethanol)."

Is this the concentration of ethanol in what you usually drink ? If so it would explain some otherwise puzzling phenomena.

Peter

I believe that is the density of ethanol.

That method would report the methanol content as if the beverage was 100% ethanol. Then it could be corrected for the ethanol content of the actual wine. So if you have 10ppm Methanol by the test and the wine was 10% ethanol then there would be 1ppm Methanol in the bottle of wine.

Sounds like typical government agency, make reporting units something totally obscure that no one recognizes just to give another hoop to jump through )

"The concentration of ethanol in alcohol drinks is always absolutely accurate and it is 789270 mg per liter of absolute alcohol (ethanol)."

Is this the concentration of ethanol in what you usually drink ? If so it would explain some otherwise puzzling phenomena.

Peter

I believe that is the density of ethanol.

That method would report the methanol content as if the beverage was 100% ethanol. Then it could be corrected for the ethanol content of the actual wine. So if you have 10ppm Methanol by the test and the wine was 10% ethanol then there would be 1ppm Methanol in the bottle of wine.

Sounds like typical government agency, make reporting units something totally obscure that no one recognizes just to give another hoop to jump through )

It is indeed the density of ethanol (at a particular temperature), and confusing density with concentration is not a good start for accurate results, even if using the ethanol that is already in the drink as an IS did not violate several well established analytical principles.

Peter

...Sounds like typical government agency, make reporting units something totally obscure that no one recognizes just to give another hoop to jump through )

In fact this unit has got sense. Permissible methanol content in alcoholic drinks is connected with ethanol concentration. The more concentrated ethanol, the more methanol content is permissible - that's why this calculation for absolute ethanol is used. Nb. for accidents with methanol intake, the remedy is ethanol.

...Sounds like typical government agency, make reporting units something totally obscure that no one recognizes just to give another hoop to jump through )

In fact this unit has got sense. Permissible methanol content in alcoholic drinks is connected with ethanol concentration. The more concentrated ethanol, the more methanol content is permissible - that's why this calculation for absolute ethanol is used. Nb. for accidents with methanol intake, the remedy is ethanol.

@ dblux_ Not so simple.
Ethanol containing products are an excisable products. So, accounting for such goods is carried out in terms of absolute ethanol.

Direct correct determination of volatile compounds in spirit drinks are calculated in accordance with the following simple formula.

Concentration of methanol = RRF * “peak area of methanol” / “peak area of ethanol” * “concentration of ethanol in pure ethanol” [mg/l (AA)].

RRF for ethanol approximately = 1,2.
Concentration of ethanol in pure ethanol = 789270[mg/l (AA)].

There are the following examples for your attention.

There is chromatogram of Vodka.

Linear scale.


The same chromatogram of vodka in logarithmic scale.

Concentration of methanol in Vodka = 1,2 * 789270 * “peak area of methanol” / “peak area of ethanol” = 1,2*789270*(2,677E004/2,19E009) = 11,6 [mg/l (AA)].

There is chromatogram of some brandy.

Linear scale.


The same chromatogram of brandy in logarithmic scale.

Concentration of methanol in brandy = 1,2 * 789270 * “peak area of methanol” / “peak area of ethanol” = 1,2*789270*(9,539E004/1,501E008) = 601,9 [mg/l (AA)].

It should be noted that in the above formula are absent the following major parameters:
- injection value of the sample,
- model, technical characteristics and methodic parameters of used GC (split ratio, values of air and hydrogen flows for FID),
- volume concentration (v/v) of ethanol (strength) in the sample,
- quantity of injected IS.

Of course, it is always possible to clarify the RRF values directly for your GC and the methodological parameters that you use. The following is an example of a chromatogram of a calibration mixture (see Commission Regulation (EC) No 2870/2000).

Linear scale.


Logarithmic scale.

Calculation of RRF values is given below.


Is there anything else a method that can be simpler, cheaper and at the same time more certain?

Regards,
Siarhei

That gives a value of methanol relative to ethanol, and if that is what is regulated that works great and is simple.

However it does not tell how many mg of methanol are in 1L of the actual wine, unless you know the amount of ethanol in the actual wine. The original post was asking how to measure methanol in wine and wine is not equal to absolute alcohol since it normally is a mixture with approximately 15% ethanol and 85% water.(with many other constituents of course)

...The original post was asking how to measure methanol in wine and wine is not equal to absolute alcohol since it normally is a mixture with approximately 15% ethanol and 85% water.(with many other constituents of course)

Yes, but seems to me that original poster was a one time visitor here from May 2nd. Lets assume that he or she is no more interested in this analysis

...@ dblux_ Not so simple.
Ethanol containing products are an excisable products. So, accounting for such goods is carried out in terms of absolute ethanol.
...
Regards,
Siarhei

Taxes have nothing in common with permissible methanol content in alcoholic drinks.

@ dblux_ The fact that spirit drinks are excisable goods has led to the fact that the values of concentrations of volatile components need to be determined in mg per liter of absolute ethanol [mg/l (AA)] (see REGULATION (EC) No 110/2008 and COMMISSION REGULATION (EC) No 2870/2000). A detailed description of this circumstance is presented here https://www.youtube.com/channel/UCXgL2c ... lW1oxOGqtQ .

@ James_Ball The concentration in mg/l can be easy obtained by the following simple formula:

Concentration of methanol[mg/l] = concentration of methanol[mg/l (AA)] * “strength [%]”/100[%].

As a consequence, in the case given by You with approximately 15% ethanol, the calculated value of the methanol concentration in the dimension of the [mg/l] will be 15/100 times the concentration in the dimension of ”[mg/l (AA)].

Regards,
Siarhei

@ dblux_ The fact that spirit drinks are excisable goods has led to the fact that the values of concentrations of volatile components need to be determined in mg per liter of absolute ethanol [mg/l (AA)] (see REGULATION (EC) No 110/2008 and COMMISSION REGULATION (EC) No 2870/2000). A detailed description of this circumstance is presented here https://www.youtube.com/channel/UCXgL2c ... lW1oxOGqtQ .
...Siarhei

Siarhei, the above mentioned regulation doesn't explain why methanol content is expressed in mg/L (AA). It only arbitrarily introduces such unit what we took for granted.
Would you be so kind and post here an excerpt from regulation you linked clearly stating the reason of expressing methanol in relation to absolute ethanol ?
TIA

@ dblux_ The fact that spirit drinks are excisable goods has led to the fact that the values of concentrations of volatile components need to be determined in mg per liter of absolute ethanol [mg/l (AA)] (see REGULATION (EC) No 110/2008 and COMMISSION REGULATION (EC) No 2870/2000). A detailed description of this circumstance is presented here https://www.youtube.com/channel/UCXgL2c ... lW1oxOGqtQ .

@ James_Ball The concentration in mg/l can be easy obtained by the following simple formula:

Concentration of methanol[mg/l] = concentration of methanol[mg/l (AA)] * “strength [%]”/100[%].

As a consequence, in the case given by You with approximately 15% ethanol, the calculated value of the methanol concentration in the dimension of the [mg/l] will be 15/100 times the concentration in the dimension of ”[mg/l (AA)].

Regards,
Siarhei

If you are working from an unknown product you will have to run an analysis to determine ethanol concentration then run the methanol test afterwards. Here we would just have ethanol and methanol in a standard and run them both at the same time in one injection.

@ dblux_ The fact that spirit drinks are excisable goods has led to the fact that the values of concentrations of volatile components need to be determined in mg per liter of absolute ethanol [mg/l (AA)] (see REGULATION (EC) No 110/2008 and COMMISSION REGULATION (EC) No 2870/2000). A detailed description of this circumstance is presented here https://www.youtube.com/channel/UCXgL2c ... lW1oxOGqtQ .
...Siarhei

Siarhei, the above mentioned regulation doesn't explain why methanol content is expressed in mg/L (AA). It only arbitrarily introduces such unit what we took for granted.
Would you be so kind and post here an excerpt from regulation you linked clearly stating the reason of expressing methanol in relation to absolute ethanol ?
TIA

Dear Dblux_ ,
Ok.
Below are a few screenshots from the official recognized documents.




(from REGULATION (EC) No 2870/2000)


(from REGULATION (EC) No 110/2008)



Probably enough.

In logic and mathematics, there is a method of proof by contradiction.
Let's try this approach.
Imagine only for a moment, how many problems for alcohol industry appear in the transition of the presentation of data on alcohol production in terms of liter. Ask OIV. It is better not to try.

Regards,
Siarhei