Optical non-contact pH measurement in cell culture with sterilizable, modular parts

A non-contact real time pH measurement using fully modular optical parts is described for phenol-red medium cell cultures. The modular parts can be sterilized, and once the measurement is started at the beginning of culture, no recalibration or maintenance is needed till the end of the culture. Measurements can be carried out without any special manual attention. The modular assembly of LED and sensor cassettes is unique, robust, reusable and reproducible. pH is measured in an intact closed flow system, without wasting any culture medium. A special pump encapsulation enables the system to be effortlessly functional in extremely humid incubator environments. This avoids lengthy sample tubings in and out of the incubator, associated large temperature changes and CO₂ buffering issues. A new correction model to compensate errors caused e.g. by biolayers in spectrometric pH measurement is put-forward, which improves the accuracy of pH estimation significantly. The method provides resolution down to 0.1 pH unit in physiological pH range with mean absolute error 0.02.