A new optical technique developed by researchers at the University of St Andrews and Adelaide University allows toxic methanol in alcoholic spirits to be detected without opening the bottle.
Published in the Journal of Physics: Photonics; this new work offers a powerful new tool for tackling counterfeit alcohol and improving consumer safety worldwide.
Methanol contamination of spirits such as whisky, gin and vodka causes hundreds of deaths each year and can lead to serious physical consequences, such as blindness. Recent high-profile incidents have highlighted the danger: in 2024, six tourists died in Laos after drinking alcohol later found to be contaminated with methanol. It is estimated that methanol poisoning has caused tens of thousands of deaths globally, with incidents documented in nearly 80 countries.
Despite this, gold standard tests for methanol detection are time-consuming and expensive, requiring trained personnel and specialised laboratory equipment.
However, in a groundbreaking development, researchers have developed a laser-based method that can detect methanol in alcoholic spirits without ever opening the bottle, even when the glass is coloured.
The proposed approach is based on Raman spectroscopy, which allows the unique chemical fingerprint of each spirit to be identified. By carefully shaping the laser beam and tuning its wavelength, the team can suppress unwanted signals from the glass bottle and isolate the chemical signature of the liquid inside.
Lead author, Ané Kritzinger from the School of Physics and Astronomy at the University of St Andrews, said: "This work shows that we can look inside a sealed bottle and determine its methanol content, without needing to open it. By carefully shaping the laser light into a ring, and slightly tuning its colour during the measurement, we can isolate the signature of methanol and suppress the signals from both the bottle and the main spirit.
Crucially, it works across a wide range of real-world bottles, including green, brown and blue glass, where previous methods have struggled. It can be used for both colourless spirits like gin and vodka as well as coloured alcohols like whisky. This allows us to quantify methanol concentrations with a limit of detection of 0.2% – ten times lower than the human safety limit".
Dr Graham Bruce from the School of Physics and Astronomy who co led the research, said: "This technology opens the door to rapid, non-invasive screening for food and chemical safety, or for fighting the illegal trade in counterfeit spirits, pharmaceuticals or perfumes"
The work builds on earlier research from the St Andrews group that demonstrated authentication of spirits through clear glass bottles. By overcoming the challenges posed by coloured glass and fluorescence, the new study represents a significant step towards practical, real-world deployment.
PhD student Kritzinger has already received national recognition for this work. She was awarded a Gold Medal in the Physics category at STEM for Britain 2026, a competition in which young researchers communicate their science to Members of Parliament at Westminster. Following a further round of competition with the winners of each category, Ané was presented with the prestigious Westminster Medal by the Parliamentary and Scientific Committee at the Houses of Parliament, highlighting both the scientific impact and societal importance of the research.
As well as improving safety in the drinks industry, the researchers expect the technique to have wider applications. The same approach could be used to analyse pharmaceuticals, cosmetics, and other packaged goods, enabling non-destructive quality control and authenticity checks across multiple sectors.
