wine analyse with gc

[CharapitsaS]

@ 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.

Dear James_Ball,

carefully follow the text.

The volume content of ethanol in the unknown alcohol product is confidently known and is equal to 789300 mg per liter of ethanol. As a consequence, it is possible to determine the methanol content of an unknown sample in one measurement on a gas chromatograph with equipped with FID.

Does not matter the type of drink and its strength. The possibility of a new proposed method makes it possible to calculate the content of volatile compounds in the sample quite accurately at once http://inp.bsu.by/calculator/vcalc.html .
The competition of GC manufacturers has led to the fact that the values of the RRF already are very stable for each model of the GC and they could be tabulated.

The procedure for introducing the IS substance into the analyzed sample is completely absent. And after that is it possible to give up such happiness?


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

Nobody neglects that methanol content is expressed in relation to absolute ethanol.
But you linked 110/2008 regulation as a proof of of such unit as a result of taxes. It's not true and you can't justify your thesis or rather supposition.

[Peter Apps]

"The volume content of ethanol in the unknown alcohol product is confidently known and is equal to 789300 mg per liter of ethanol."

Sorry, but this is just nonsense. mg is not a unit of volume and so a volume fraction cannot be expressed in mg/l. 789300 mg/l is the density of ethanol. It is the mass of 1 l of ethanol. Since this is constant at a given temperature your statement is equivalent to claiming that all alcoholic drinks have the same ethanol content.

Peter

[CharapitsaS]

"The volume content of ethanol in the unknown alcohol product is confidently known and is equal to 789300 mg per liter of ethanol."

Sorry, but this is just nonsense. mg is not a unit of volume and so a volume fraction cannot be expressed in mg/l. 789300 mg/l is the density of ethanol. It is the mass of 1 l of ethanol. Since this is constant at a given temperature your statement is equivalent to claiming that all alcoholic drinks have the same ethanol content.

Peter

Dear Peter,

thanks for Your remarks.
Of course, "The volume content of ethanol” in alcohol products is expressed in % (v/v). Generally accepted units. Undoubtedly, the following correct assertion holds “The concentration of ethanol (g/ 100L (AA)) is known with a 100% guarantee and is equal to ethanol density (78927 grams per 100 liters)”.
And after that, with Your assertion that ”all alcoholic drinks have the same ethanol content” can not be disagree.
Mind games.

I have to repeat myself once again, as a praying person, the method offers users the following undeniable advantages:
1) the internal standard is always available,
2) there is no need to add any internal standard substance in the standard solutions prepared for the calibration of the GC as well as in the test sample, because ethanol is always present in spirit drinks,
3) the value of the uncertainty of the concentration of IS is zero. 100% satisfaction guarantee,
4) for modern GC the values of the RRF relative to ethanol can be tabulated (see, for example, http://chromforum.org/viewtopic.php?f=2&t=24445).

Is this not enough to try this method?

Regards,
Siarhei
(svcharapitsa@tut.by)

[Peter Apps]

“The concentration of ethanol (g/ 100L (AA)) is known with a 100% guarantee and is equal to ethanol density (78927 grams per 100 liters)”.

This is true only for absolute ethanol. Alcoholic beverages are not absolute ethanol. Therefore it is not true for alcoholic beverages. Therefore we do not know the concentration of ethanol in any alcoholic beverage unless we measure it.

Peter

[dblux_]

“The concentration of ethanol (g/ 100L (AA)) is known with a 100% guarantee and is equal to ethanol density (78927 grams per 100 liters)”.

This is true only for absolute ethanol. Alcoholic beverages are not absolute ethanol. Therefore it is not true for alcoholic beverages. Therefore we do not know the concentration of ethanol in any alcoholic beverage unless we measure it.

Peter

Although alcoholic beverages are certainly not absolute ethanol, they always contain certain amount of it - depends on concentration.

No matter what is the real concentration of ethanol solution when we calculate mass of ethanol related to it's volume in alcoholic drink we will always get a constant value (at a given temperature).

When we proportionally recalculate mass of ethanol in relation to volume of ethanol set arbitrarily to 100 L we will always get 78927 grams.

However we still don't know it's real concentration.
Concentration (or in this case strength) has to be measured (!) and the official method is by measuring density (either directly, or in case of beverages containing sugars etc. by measuring densities of distillates).

In other words 78927 g/100 L (AA) is not a concentration. It has other physical meaning and is simple a mass of 100 liters of 100% ethanol at 20 degC.

[MSCHemist]

I don't get what the big fuss is about. just make an analytical standard of methanol and ethanol and measure it rather than assume methanol and ethanol have equal relative response area counts. My ethanol method is one of the simplest I perform so long as you find an ideal column adding methanol shouldn't be a big issue.

[Andy F]

The potential problem would be that the method would need to be able to analyse ethanol at around 40 % abv and also be able to measure methanol at mg/l levels.

[MSCHemist]

The potential problem would be that the method would need to be able to analyse ethanol at around 40 % abv and also be able to measure methanol at mg/l levels.

yea that would be a problem. The only solution would probably be two GC runs with either with different sample dilutions or one with a high split ratio. The only other option would be a GC with some sort of capillary flow splitting setup where a very small fraction injected is split onto a second column with a second detector.

[James_Ball]

@ 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.

Dear James_Ball,

carefully follow the text.

The volume content of ethanol in the unknown alcohol product is confidently known and is equal to 789300 mg per liter of ethanol. As a consequence, it is possible to determine the methanol content of an unknown sample in one measurement on a gas chromatograph with equipped with FID.

Does not matter the type of drink and its strength. The possibility of a new proposed method makes it possible to calculate the content of volatile compounds in the sample quite accurately at once http://inp.bsu.by/calculator/vcalc.html .
The competition of GC manufacturers has led to the fact that the values of the RRF already are very stable for each model of the GC and they could be tabulated.

The procedure for introducing the IS substance into the analyzed sample is completely absent. And after that is it possible to give up such happiness?


Regards,
Siarhei

This makes sense to calculate the amount of methanol relative to the amount of ethanol, but the original question was how much methanol is in wine. If methanol is at a concentration of 1ppm and ethanol is at 12%, which would be 120,000ppm, then the ethanol peak is going to be off scale and the methanol peak barely visible.

To use an internal standard (ethanol) you need to know its concentration in the total volume of sample(wine) then you can calculate the concentration of methanol. If you don't first know the concentration of ethanol then the concentration of methanol in the total wine can't be calculated.

Also we have to verify the RRF each day because the RRF between two compounds is not a constant, even on the best instruments. Any change in separation, flow rates, columns and other factors can cause variations in the RRF between two different compounds.

[CharapitsaS]

This week I received the measured chromatograms of the last scheduled calibration performed at the distillery.
Based on the experimental data obtained from the profile laboratory, the following explanatory material has been prepared.


Fig. 1. The basic documents, which regulate volatile compounds determination.


Fig. 2. An example of one of the unsolved problems.


Fig. 3. The practical solution to this problem.


Fig. 4. New is learned in comparison.


Fig. 5. Mathematical proof of increasing the reliability of the obtained measurements.


Fig. 6. The concentrations in the prepared standard solutions (40% v/v).
From the concentrations of volatile components in vodka (water-ethanol solutions WES-3) to brandy and raw alcohol (WES-A).


Fig. 7. The experimental data obtained for determining the values of RRF.


Fig. 8.


Fig. 9.


Fig.10.


Fig.11. The results of experimental tests of standard solutions by the traditional method and by a new method.

As new original experimental data are obtained, the results will be supplemented.
Naturally, I am ready to give explanations immediately on the specific situations sent to me by e-mail svcharapitsa@tut.by .

Regards,
Siarhei

2017-05-29.
Data on the testing of standard solutions of ethanol rectified (ER) from food raw materials (96 % v/v) were obtained. The results are presented in Figures 12-14.


Fig. 12.


Fig. 13.


Fig. 14.