Optical technique detects methanol through sealed spirit bottles
Researchers at the University of St Andrews and the University of Adelaide have developed an optical technique capable of detecting toxic methanol in alcoholic spirits without opening the bottle, potentially offering a new tool for tackling counterfeit alcohol and improving consumer safety.
The work, published in the Journal of Physics: Photonics, uses Raman spectroscopy to identify the chemical fingerprint of liquids inside sealed bottles, including those made from coloured glass.
Methanol contamination remains a significant global health issue, causing hundreds of deaths each year and leading to serious health consequences including blindness. Existing laboratory methods for methanol detection are generally time-consuming, costly and reliant on specialist equipment and trained personnel.
The researchers have now demonstrated a laser-based approach that can detect and quantify methanol without opening the container.
The technique relies on Raman spectroscopy, which identifies substances based on their unique molecular signatures. By shaping the laser beam into a ring and carefully adjusting its wavelength, the team was able to suppress optical interference from the bottle itself and isolate signals from the liquid inside.
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.”
According to the researchers, the method works with a range of bottle colours, including green, brown and blue glass, where previous approaches have struggled. It can also be applied to both colourless and coloured spirits, including vodka, gin and whisky.
The team reports a methanol detection limit of 0.2%, which they say is ten times lower than the threshold considered hazardous to human health.
Dr Graham Bruce, who co-led the study, said the technology could have applications beyond the drinks industry.
“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,” he said.
The work builds on earlier research from the St Andrews group focused on authenticating spirits in clear glass bottles. By addressing the challenges posed by coloured glass and fluorescence, the researchers believe the latest study represents an important step towards real-world deployment.
Beyond alcohol testing, the team expects the technique could be applied to pharmaceuticals, cosmetics and other packaged products where non-destructive quality control and authenticity verification are required.
Pic: Reiseuhu
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