Abstract
Electronic nose (E-nose) technology provides an easy and inexpensive way to analyse chemical samples. In recent years, there has been increasing demand for E-noses in applications such as food safety, environmental monitoring and medical diagnostics. Currently, the majority of E-noses utilise an array of metal oxide (MOX) or conducting polymer (CP) gas sensors. However, these sensing technologies can suffer from sensor drift, poor repeatability and temperature and humidity effects. Optical gas sensors have the potential to overcome these issues. This paper reports on the development of an optical non-dispersive infrared (NDIR) E-nose, which consists of an array of four tuneable detectors, able to scan a range of wavelengths (3.1–10.5 μm). The functionality of the device was demonstrated in a series of experiments, involving gas rig tests for individual chemicals (CO2 and CH4), at different concentrations, and discriminating between chemical standards and complex mixtures. The optical gas sensor responses were shown to be linear to polynomial for different concentrations of CO2 and CH4. Good discrimination was achieved between sample groups. Optical E-nose technology therefore demonstrates significant potential as a portable and low-cost solution for a number of E-nose applications.
Highlights
The electronic nose (E-nose) has been in continuous development since its conception in the early 1980s by Persaud and Dodd [1]
This operating principle attempts to mimic the function of biological olfactory receptors by analysing samples as a whole, rather than individual chemicals
We show the development and testing of a novel optical-based E-nose, with an array of non-dispersive infrared (NDIR) detectors
Summary
The electronic nose (E-nose) has been in continuous development since its conception in the early 1980s by Persaud and Dodd [1]. The term E-nose describes an instrument consisting of an array of cross-sensitive gas sensors, coupled with a pattern recognition approach This operating principle attempts to mimic the function of biological olfactory receptors by analysing samples as a whole (so-called “odour fingerprints” [2]), rather than individual chemicals. Two other major application areas for E-noses have emerged; environmental monitoring (e.g., detecting pollutants, hazardous chemicals and/or explosives) [4] and biomedical purposes (e.g., monitoring and diagnosing diseases) [5]. These applications rely on the ability of E-noses to generate a holistic analysis of a gas-phase mixture, which are made up of volatile organic compounds (VOCs) and some non-VOCs, such as inorganic gases. VOCs can be broadly defined as carbon-based compounds (C2 –C30 ), which include a diverse group of compounds such as hydrocarbons, esters, alcohols, ketones and aldehydes, with high vapour pressures and low boiling points (50–260 ◦ C) [6]
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