Analyte-selective optode membranes and optical evaluation techniques: characterization of response behavior by ATR measurements

A variety of analyte-selective bulk membranes for use in optodes have been developed. They combine effectively with various optical transducers and detection techniques. Although the working principles of these membranes differ, the basic principle is a diffusion-limited exchange of the analyte between sample solution and optical bulk membrane. The thickness and viscosity of the membranes govern the diffusion and, therefore, the response time of the sensor. In accord with analytical requirements, the specifications of optode membranes can be predicted from measurements of the overall diffusion coefficients in the membrane phase. The ATR-approach is shown to be an attractive technique for such investigations.