Fluorescent Carbon Dioxide Indicators

Abstract

There are few analytes in the world as significant as carbon dioxide, equal, as it is, in importance as oxygen and pH. Carbon dioxide is a basic chemical feedstock of life, which when coupled with green plant photosjoithesis1, i.e. $$ CO_2 + H_2 O\xrightarrow{{sunlight}}C(H_2 O) + O_2 $$ (1) where C(H20) is a reduced form of carbon such as a sugar or starch, generates the fuel and food necessary for the continued existence of most known forms of life. The reverse of reaction (1) is the basis of most cell metabolism, releasing, as it does, the energy for life. Thus, not only is carbon dioxide usually an essential ingredient to make the prerequisite chemicals for life, it is also often used as an indicator of the existence of life and a measure of health. For example, in medicine, the key, basic analytes that are routinely monitored in the blood of hospital patients are: dissolved oxygen, pH and carbon dioxide2. In clinical chemistry, a whole area devoted to the monitoring of the levels of carbon dioxide in breath has emerged, i.e. capnography, in which not only the level of carbon dioxide is important, but also its temporal variation, since both provide valuable medical diagnostic information3.