<title>Robust carbon dioxide optrode based on a covalently immobilized pH indicator</title>

An optical chemical sensor for dissolved carbon dioxide has been developed whose dynamic range was adjusted to CO₂ partial pressures ranging from 0 to 100 hPa. The change in the pH of a buffer layer, caused by diffusion of carbon dioxide through a hydrophobic membrane, is indicated by the color change of a covalently immobilized dye and monitored through optical fibers. The sensor also incorporates an optical insulation with a resplendent pigment to increase the reflectivity and to reduce adverse effects of straylight and ambient light. Two methods for layer manufacturing (spreading and spin coating) are described. The sensor membrane is fully LED compatible. The optrode shows a promising performance with respect to chemical and mechanical long-term stability, reproducibility, and sterilizability.