How to test for methanol?

[Maderie]

I'm in grade 12 and doing a project on the dangers of aspartame. When drinks like Tab, Coke light, Sprite Zero are heated (in the sun) (also the sweetner Canderel) {of which all of the above mentioned contains Aspartame} it breaks down in methanol and aldehyde. I want to test the methanol to show that the Aspartame is dangerous. Can you please tell me if there is easy method on how to do a methanol test? I would really appreciate your help!

[donnahardy2]

Hi,

This is a fascinating and timely project idea. Unfortunately, the analysis of aspartame is usually done by high pressure liquid chromatography on a reversed phase C8 or C18 column. And analysis of methanol and benzaldehyde is usually done by HPLC analysis on a different type of column or by gas chromatography. Here is some information on the products that are used:

aspartame analysis:

http://www.chem.agilent.com/Library/app ... 660741.pdf

benzaldehyde by GC; methanol can also be analyzed by this method

http://www.wnho.net/benzaldehyde_formation.pdf

Having access to HPLC and GC equipment would be helpful for doing this project. However, the columns used are very expensive, usually costing over $1000, so you would need to borrow a column for a few samples or apply for a grant so you could purchase them. Do you have access to a research laboratory, or perhaps an environmental testing lab with a lab technician who could help you? If not, then ask your teacher, parents, and friends for a referral and find out if this is a possibility for you.

If access to a lab is not possible, then there are probably alternative methods for analysis, perhaps a colorimetric procedure, for example, that could be used. I can help you look for a suitable alternative method. Does your school have a spectrophotometer? Please let me know what type of equipment you have available to use. For a science project, you need a quantitative method to measure your results.

You have identified an excellent topic for your project; the next challenge will be to adapt it to the resources that you have available. Please let me know about the experiment that you have in mind. Do you know what concentration of aspartame, methanol, and benzaldehyde you would need to detect? What is the question that you want to answer with your experiment? What is your hypothesis? You will need a very carefully designed, controlled experiment for this project.

Donna Hardy

[donnahardy2]

Hi,

Here is a possible alternative for HPLC or GC analysis for your aspartame to methanol/benzaldehyde project.

Since you are a senior, I’m sure you have had a chemistry class. Here is another chemistry lesson.

The Wikipedia article on aspartame includes its molecular structure. Please note that aspartame has a benzene ring (C6H6), which means that it will absorb UV light at 280 nm. You could quantitate the molecule by using a spectrophotometer or microplate reader that can read samples at 280 nm. You would set up a standard curve with increasing concentrations of aspartame and then measure the UV absorbance of your standards and samples, and interpolate the aspartame concentration of the samples from the standard curve.

http://en.wikipedia.org/wiki/Aspartame

Here is a website that lists methods for measuring methanol in biological samples. Methanol can be quantitated by oxidizing it to formaldehyde, and then reacting it with chromotropic acid and sulfuric acid and measuring the optical density at 570 nm. A standard curve would be run to give quantitative results.


http://www.inchem.org/documents/pims/ch ... 35.htm#8.2

I would try the above method with an unoxidized sample to quantitate the benzaldehyde, but if for some reason it did not work, here is a website that describes a method for measuring benzaldehyde using a titration of the hydrochloric acid, which is released from a solution of hydroxylammonium chloride. This analysis would require using a pH indicator such as phenolphthalein or a pH meter.

http://pubs.acs.org/doi/abs/10.1021/i560102a025

It might be a lot easier to find a spectrophotometer or microplate reader and the various chemicals needed for the analysis compared to an HPLC or GC system. If you think you want to pursue these options, try looking for references that give a little more detail about the analytical method. The websites I found give general descriptions only.

Also, I recommend using a solution of pure aspartame in water for one of your samples. You also need to check the labels for the Tab, Coke, and Sprite Zero to make sure they don’t contain any ingredients that would interfere with the spectrophotometric analysis of your analytes.

I hope this makes sense to you. Please let me know if you have any questions.

Donna Hardy

[Maderie]

Thank you so much for all your help so far, I really do appreciate it a lot.

I talked to someone at the nearest University about the methanol test and she told me that the only way is the GC analysis and that it is too expensive so that would not work.

My resources is very limited and our school lab's resources is also very limited. I do not think that our school has a spectrophotometer and it is holiday here at the moment so I cannot talk to my teacher.

What I want do do is the following:
Take Tab, Coke Light, Sprite Zero and Canderel sachets dissolved in water (of whom all contains Aspartame) and Coke for the control (which contains no Aspartame).
Place this solutions in the sun for example for 2 hours. (The heated effect breaks the Aspartame in 10% methanol and formaldehyde.)
Then I wanted to do the methanol test on the solutions of Tab, Coke Light, ect. to show that it now contains methanol which is toxic.
Can you help me find an easy method to show that methanol is present?
If there is no easy way to test the methanol, is there maybe any other thing that I can do to show that Aspartame is toxic and dangerous for human kind?

My hypothesis may still change according to what is able to test. The main idea is that when the products which contains Aspartame is heated, the Aspartame breaks into its components which is toxic. I just need a practical experiment on this subject.

I will appreciate your help!

[donnahardy2]

Hi,

There is another possibility that you can try. Methanol has a lower density compared to water, so you should be able to measure the conversion of aspartame to with a hydrometer. Why don’t you see if you can borrow a selection of hydrometers; you will need one that will measure the specific gravity of the samples you are testing?

http://en.wikipedia.org/wiki/Hydrometer

http://en.wikipedia.org/wiki/Relative_density

You will definitely need to do a pilot experiment to verify this method will work for your samples, but it should be an excellent quantitative method.

Please let me know if you have access to hydrometers. If not, I’ll try to think of an alternative method.


Donna Hardy

[John Dreher]

You might find some useful background information, especially about methanol and aspartamine at

http://www.ajcn.org/content/46/1/204.short

This is the abstract, the full review paper can be downloaded for free using the appropriate link on the page.

[John Dreher]

Another method to find methanol might be to distill it out. (I am NOT a chemist, so this may be all wrong, but Donna can correct me in that case.) Methanol has a boiling point (at 1 atmosphere) of 65 C, much less than that of water (100 C). So by placing a flask containing methanol and water in a 65 C water bath, the methanol would be driven off and the vapors converted back to a liquid in a condenser. I'm not well enough versed in physical chemistry to calculate the enrichment factor of the methanol/water ratio in the condensate, but I'd guess it would be pretty substantial. Then the whole process could be repeated on the 1st stage condensate, which might end up producing mostly methanol. Then you just need a gross, qualitative detector for methanol vs water; maybe just light it with a match ?

Perhaps fractionation by freezing would be even better. Methanol has a freezing point of -97 K. An ice/acetone bath or a block of dry ice should freeze out the water and leave the methanol as a liquid. The problem, I'd guess, would be extracting the small amount of liquid from the solid ice; at a guess you'd need to crush it while keeping it cold, perhaps working in a walk-in freezer.

Maybe a combination would work best: enrich the methanol/water level using distillation until the result is ~50% methanol, then freeze it leaving chunks of water ice floating (or sinking?) in relatively pure methanol.

I would imagine the test protocol to use samples of distilled water, samples of water with varying amounts of pure methanol, then water dosed with various amounts of aspartamine reacted in an aluminum can at the appropriate temperature to create the methanol, if any.

Yet another half-baked idea: use a "Breathalyzer", either one borrowed from a police department or the commercial variety intended for home use. The former use infrared spectroscopy and might be too specific to ethanol, but the solid state sensors used in the domestic units might react to methanol as well as ethanol -- a call to the manufacturers might answer that question.

[donnahardy2]

Hi,

John has given you some really good suggestions! Distillation would recover any volatile compound, including methanol, but would be challenging to do with the small quantities, but theoretically should work.

http://homedistiller.org/howitworks.pdf

For an analytical method, measuring the freezing point carefully and accurately could measure small quantities of methanol. Methanol depresses the freezing point of water, so you could use this method to estimate the methanol concentration.

http://www.engineeringtoolbox.com/metha ... d_987.html

The breathalyzer is a really unique idea, and yes, methanol definitely reacts with the dichromate in this instrument. You might be able to adapt the breathalyzer for your samples; I think you would need to heat your samples.

http://www.borkensteincourse.org/facult ... ogic%209(4)%201984.pdf

Are any of the options feasible for you to do? Please let us know.


Donna Hardy

[Craig_Bridge]

IMO: Simple distallation or any method that involves heating is NOT going to work for this problem. The process of heating is going to cause any aspartame to break down. GC probably can't be used for the same reason. HPLC requires the use of a solvent, and the common one methanol, can't be used. This means you can't use HPLC columns that have previously had a methanol solvent used in them. This is a non-trivial chemical analysis problem.

[Maderie]

Thank you all your help. I went to a university and they helped me to do tests on the GCMS.
Thanks!

[donnahardy2]

Hi Maderie,

Thanks so much for letting us know that you were able to do your project. That's great that you had access to GC-MS. This should have given you accurate and very sensitive measurements. What did your results show?

Donna Hardy

[Maderie]

Hi,

My results was actually dissapointing because no methanol was shown, but the reason for this was that the sweetner was heated too much (it was placed in the microwave for 1 minute)and I think that the methanol evaporated since its boiling point is only 65˚C. But then I came to the conclusion that when you place the sweetner in your coffee or tea (which is of course heated) the methanol evaporates and cause no harm to humankind.
If I had more time, I would certainly improved the experiment by not heating it in the microwave or by placing it in a closed container.
Again thank you for all your help.

Maderie

[donnahardy2]

Hi Maderie,

You are welcome! Thanks for letting us know what happened in your project. While it is disappointing that you did not prove your hypothesis, it’s good that you have an explanation for what may have happened. This was an original and unique project and I think you did a really good job on a challenging topic.

Good luck to you in the future!

Donna