THEORY AND PRACTICE IN OPTICAL PH SENSING

Optical pH sensors (pH optodes) are based upon pH-dependent changes of the optical properties of thin proton-permeable layers. Most research on pH optodes has been carried out on pH optodes for use in the physiological pH range. However, in recent years, the working range has been extended to other pH ranges as well. The basic technology, performance characteristics and design parameters of specific pH optodes are illustrated. Practical problems associated with instrumental difficulties as well as physical and chemical interferences such as background signals, accuracy and drift, time response, system calibration and durability are discussed.