Don's Diary

Thursday. Conference season is over at last! I have just returned from the fifth Symposium on Electronic Noses, held in Baltimore this year. There were about 200 people there - manufacturers, researchers, users of electronic nosesI It seems that bad smells are big business. There were applications in food quality control - rancidity in fats seems to be big trouble. Another problem is benzene in bottled water. I always wonder how manufacturers manage to contaminate their product in this way. The withdrawal of some fizzy drinks from supermarket shelves this year prompted a flurry of activity in analytical laboratories across the United Kingdom. Somehow we need to design instruments more sensitive than the human nose.

Friday

Back to university life. There is a horde of students milling outside, all bright and fresh, and it is out with my lecture notes and a fresh set of coloured pens for the first of this year's lectures. Two hours in and they already look dazed, so it is time to call a halt and investigate what is happening in the laboratory. There, bad smells abound - we are busy with a project in collaboration with Silsoe Research Institute and the Institute of Grassland and Environmental Research on how to measure agricultural malodours with electronic nose technology.

When you drive down the motorway, the pong that suddenly hits you if a farmer has recently spread slurry on his fields is unforgettable. Our colleague at IGER has analysed the individual chemicals present in pig slurry and we have been able to reconstitute them to make a cocktail that emits an authentic pig-farm smell. Since we are busy testing sensors that can detect and measure smells, our cocktail is very useful.

Monday

At SRI, our colleagues test people's sense of smell - panels of sniffers are grouped around an olfactometer. This instrument dilutes odour until the human nose can no longer detect it. Huge transparent bags of odour arrive from sewage treatment works and pig farms. Some of the panellists are experts in the nuances of such odours. Can our sensors measure such smells? To a limited extent, but we are far from an instrument that can match the human nose. Back to the drawing board!

Tuesday

The laboratory is bubbling over. One of our sensor materials has proved to be extremely sensitive to compounds that smell like dirty drains. It is time to mount a set into a sensor array and test it as part of an instrument.

Wednesday

We wait with bated breath. We attach a vapour-generation system to our instrument. Thousands of data points pour into the computer memory and are crunched to produce a set of squiggles. The signal looks a bit noisy, but it is definitely there - we are measuring sub parts-per-million levels of odour. Time to sniff a pint!

Krishna Persaud

Senior lecturer, University of Manchester Institute of Science and Technology.