Measure the fatal twin of ethanol

ETH researchers have come up with an inexpensive portable measuring device, able to distinguish methanol from mouthwash. It offers a quick and easy method to detect adulterated or contaminated alcoholic beverages and helps diagnose methanol intoxication by exhaled breath.

Methanol is sometimes called the deadly twin of ethanol. While the latter is the intoxicating ingredient of wine, beer and schnapps, the first is a chemical that becomes highly toxic when it is metabolized by the human body. Even a relatively small amount of methanol can cause blindness or even prove fatal if it is left untreated.

Cases of alcohol-related poisoning involving methanol occur over and over again, especially in developing and emerging countries, because alcoholic fermentation also produces small amounts of methanol. Whenever alcohol is distilled unprofessionally in garden activities, relevant amounts of methanol can end up in the alcohol. Adulterated beverages with windshield washer fluid or other methanol-containing liquids are another potential cause of poisoning.

Beverage and Breathalyzer Analyzes

Until now, methanol could only be distinguished from ethanol in a chemical analysis laboratory. Even hospitals need relatively large and expensive equipment to diagnose methanol poisoning. "These devices are rarely available in emerging and developing countries, where outbreaks of methanol poisoning are the most common," says Andreas Güntner, head of the research group at the Division's Particle Technology Laboratory. ETH, Professor Sotiris Pratsinis, and researcher at the University Hospital Zurich.

He and his colleagues have now developed an affordable portable device based on a small metal oxide sensor. It is able to detect adulterated alcohol in less than two minutes by "detecting" the vapors of methanol and ethanol contained in a drink. In addition, the tool can also be used to diagnose methanol intoxication by analyzing the exhaled breath of a patient. In case of emergency, this ensures that the appropriate measures are taken without delay.

Separate methanol from ethanol

The use of metal oxide sensors to measure alcohol fumes is nothing new. However, this method did not distinguish different alcohols, such as ethanol and methanol. "Even the breathalyzers used by the police only measure ethanol, although some devices also incorrectly identify methanol as ethanol," says Jan van den Broek, PhD student at ETH and lead author of the study.

First of all, ETH scientists have come up with a very sensitive alcohol sensor using nanoparticles of tin oxide doped with palladium. Then they used a trick to differentiate methanol from ethanol. Instead of analyzing the sample directly with the sensor, both types of alcohol are first separated into a fixed tube filled with a porous polymer, through which the ## EQU1 ## 39 Sample air is sucked by a small pump. As its molecules are smaller, methanol passes through the polymer tube faster than ethanol.

The measuring device is revealed extremely sensitive. Laboratory tests have been able to detect even traces of methanol contamination selectively in alcoholic beverages, within the lowest legal limits. In addition, scientists analyzed breath samples from someone who had already been drinking rum. For testing purposes, the researchers then added a small amount of methanol to the breath sample.

Patent pending

The researchers filed a patent application for the measurement method. They are currently working to integrate the technology into a device that can be used in a practical way. "This technology is inexpensive, which makes it also usable in developing countries, it is simple to use and can be used even without laboratory training, for example by authorities or tourists," says Güntner. It is also ideal for quality control in distilleries.

Methanol is more than just a nuisance related to alcoholic beverages, it is also an important industrial chemical, which could play an even bigger role: methanol is considered a potential fuel because vehicles can be powered with methanol fuel cells. Another application of the new technology could therefore be an alarm sensor to detect leaks in tanks.