Pattern Recognition System for E-nose

An odour is the description of the sensation perceived when volatile chemicals are sensed by the biological nose. The odours that we perceive in the world around us arise through the interaction of molecules with sensory cells located in our nose. Typically, the odour of a flower or of a foodstuff or other natural material consists of a complex mixture of molecules present in different concentrations. In other cases a single, pure chemical compound can be the dominant odour. The human nose is widely used as an analytical tool in industry today, e.g. to assess the quality of food-stuff, drinks, perfumes and many other household products. Panels are setup at sites manufacturing products with odour specifications. Despite having high performance at low concentrations the human nose cannot be used economically, because these panels are expensive to train and maintain and give subjective assessments which can be adversely affected by external parameters such as illness and fatigue. They are also unsuited for use in aggressive environments and with toxic and obnoxious odours. Furthermore, it is difficult to replicate an olfactory panel at different geographical sites. Consequently, there is considerable need for an instrument that could mimic the human sense of smell and be used in industrial applications. Gas chromatography-mass spectroscopy (GC-MS) is one of the most widely used techniques for the analysis of complex mixtures to be separated and the individual constituents identified and quantified. As the technique became widespread and more sophisticated, it was possible to separate and chemically identify the dozens or hundreds of individual substances present in food, flavour and fragrance products. However, this is a complex, expensive and time-consuming task which requires a well-equipped analytical laboratory and skilled staff. Hence, there is enormous demand for an electronic instrument that can mimic the human sense of smell and provide low-cost and rapid sensory. One of the pioneering steps, towards the concept of an electronic nose as an intelligent chemical array sensor system for odour classification, was made in 1982 by Persaud and Dodd (Persaud et al. 1982).