Colorimetric Sensors Measurement

Abstract

Despite some successes with electronic nose systems as described in Chap. 4, the limited range of sensor analyte interactions limits both their sensitivity for detection of compounds at low concentrations relative to their vapor pressures and their selectivity for discrimination between compounds; the latter proves especially problematic in interference from the large environmental changes in humidity. Recently, a new technology based on colorimetric sensor array is used for odors and volatile organic compounds (VOCs). This colorimetric sensor array was proposed by using thin films of chemically responsive dyes on porous membranes. The array of multiple dyes, whose colors change based on the full range of intermolecular interactions, provides enormous discriminatory power among odorants in a simple device that can be easily imaged digitally. This technology resurrect the analytical chemistry of a century ago by using arrays of colorimetric sensors combined with modern digital imaging and thereby create a new technological approach that has much promise for the detection and identification of food odorants and the fingerprinting of complex mixtures of food odorants. Some fundamental knowledge about colorimetric sensors measurements is introduced at first in this chapter, which include chemical basic knowledge about this technology, design of a colorimetric sensor array, and chemoresponsive dyes. Porphyrins and metalloporphyrins, two most used dyes in colorimetric senor array, are discussed for detection of organic compounds. Colorimetric sensors measurements in food are reviewed. The examples, how to develop a colorimetric sensor measurement system and how to use them for food quality and safety detection, are provided at the end of this chapter.