Odour evaluation using arrays of conducting polymer sensors.

Devices based upon the human olfactory system, comprising arrays of gas sensing elements with suitable data handling systems have shown much promise as being a viable alternative to human testing panels and established instrumental methods of assessing odours. The introductory chapter reviews the progress which has been made by various groups in developing these so called "electronic noses". Chapters 3 and 4 deal with the characterisation of a series of water-based beverages and a range of tobacco samples. The results show promise, but also that sensor response is dominated by water which masks the responses of the analyte species. Results are presented in tabular and visual form, the latter being radar plots and ribbon diagrams. When the water signals are subtracted from the raw response data, different samples show individual and different visual patterns. The promise of these results is hampered by the impression of the data, as it is clear that the problem of water interference has to be reduced for the promise of sensor arrays to be fully realised. In chapter 5, a series of structure/response mapping studies are considered. The effects of aliphatic chain length and of ring substitution are reported. Some discrimination is again evident, with water creating the same problems as in the previous studies. Throughout the work a device comprising an array of polypyrrole-based conducting polymer gas sensors was employed. Some response data has been analysed using euclidean clustering techniques to determine the individuality of sensor responses. Groups of sensors, very often pairs or threes in an array have responded in a very similar fashion.