How to test methanol in Alcoholic beverages ?

Methanol formula is CH3-OH. Methanol is very toxic and when ingested in large amounts it can cause blindness and death. Smaller volumes can damage the brain. To determine the % of methanol in alcohol is very interesting subject.

• Methanol is flammable, volatile, clear colorless liquid. Odor of methanol very similar to drinking alcohol but slightly sweeter than ethanol. (1)
• There is several methods available for the estimation of methanol in alcohol beverages using Gas Chromatography ( GC) and Fourier Transform Infrared Spectroscopy (FTIS). You can find these standard analysis methods from website of AOAC (Association of Official Analytical Communities) and ASTM ( American Society for Testing and Materials). GC method is based on the retention time which is affected by temperature, pressure and flow of carrier gases.
• In laboratory simple test to determine of methanol in alcohol is using Fehling solution. Fehling solution contains copper (II) ions complexed with tartrate ions in sodium hydroxide solution. Equation can be written as:

2 Cu 2+(in comp) + 2OH- +2e--------------Cu2O+H2O

Two drops of the methanol is added to 2-3 ml of Fehling solution and the mixture is warmed gently in hot water bath for a few minutes. (2) The blue solution produces a dark red precipitate of copper oxide (I). Because methanol reduce the complexed copper (II) ion to copper (I) oxide.

gives the overall equation:

RCHO+ 2 Cu 2+..comp + 5 OH- ----------------RCOO + Cu2O + 3H2O

References

1. Material Safety Data Sheet Number: M2015 Prepared by: Environmental Health & Safety. (U.S.A.)
2. Vogel's Textbook of Practical Organic Chemistry 4th ed by Arhur I. Vogel (1987)