OPTICAL TRIPLE SENSOR FOR MEASURING PH, OXYGEN AND CARBON-DIOXIDE

A triple sensor unit consisting of opto-chemical sensors for measureme nt of pH, oxygen and carbon dioxide in bioreactors is presented. The p H and the CO2 sensor are based on the color change of a pH-sensitive d ye immobilized on a polymeric support. The resulting changes in absorp tion are monitored through optical fibers. The oxygen sensor is based on the quenching of the fluorescence of a metal-organic dye. All three sensors are fully LED compatible. The sensitive membranes consist of plastic films and can be stored and replaced conveniently. The sensors are sterilizable with hydrogen peroxide and ethanol. In addition, the pH sensor is steam sterilizable. Accuracy, resolution and reproducibi lity fulfil the requirements for use in biotechnological applications. Calibration procedures for each sensor are presented. The working pri nciple and the performance of all three sensors are described, with pa rticular emphasis given to their application in bioreactors.