Optical sensor for alcohols raises spirits

An optical sensor that distinguishes between the vapours of different alcohols has been assembled by scientists in Thailand as an aid to the food and beverage industry. It is based on a thin film of magnesium 5,10,15,20-tetraphenylporphyrin which is fitted inside a sensor chamber positioned alongside a conventional UV-vis spectrophotometer.

The alcohol vapours are directed across one face of the film while a light source is directed at right angles towards it. The absorption spectrum of the porphyrin film is affected by electron transfer from the alcohols in such a way that the different alcohols can be identified with the aid of principal components analysis and their concentrations estimated. The system was able to differentiate between methanol, ethanol and isopropanol vapours.

The simplicity of the system lends itself to wide application, say the research team in Analytica Chimica Acta. Senior reporter Teerakiat Kerdcharoen from Mahidol University, Bangkok, reckons that their detailed instructions for preparing the films will allow scientists in food labs to make their own versions of this "optical nose."