Enhancing the performance of two different commercial CO2 indicators using digital colourimetric analysis DCA

Two different, commercial colourimetric CO2 indicators are made in the lab, namely one based on an indicator in solution for monitoring the level of dissolved CO2 in an aquarium, i.e., a drop check indicator, and another based on an ink, for monitoring the level of CO2 in breath (capnography), i.e., a correct tracheal placement indicator. The selected commercial indicators are limited currently in terms of the analytical information they provide (qualitative) as they are normally assessed by eye. Thus, in each case, for both the lab-made and commercial indicators, colour photography coupled with digital image analysis, i.e., digital colour analysis (DCA), is used to convert the colour data from the indicator into a quantitative measure of CO2 and so markedly improve the quality of the analytical information provided by original indicator. This is the first time either indicator has been studied as a quantitative analytical system. The CO2 sensitivity of each of the lab-made indicators is found to match well that of its commercial counterpart. A simple program is provided to help non-experts and experts alike to apply DCA in this way. The potential of DCA to enhance the performance of other commercial indicators is discussed briefly.