Fundamentals of enzyme substrate determinations by fiber optics spectroscopy

Usually optodes and optical enzyme sensors base on the determination of light reflected from the sensor head on an optical fiber The fundamentals for the mathematical description of the corresponding processes are given by the Kubelka -Munk function, while in practise most commonly the tambert-Beer-Bouguer’s law is applied. The response of a pH-optode with phenol red as indicator can be described by so-called ‘F-diagrams’ derived from the Kubelka-Munk function, however, the evaluation of the reflection measurements by the Lambert-Beer-Bouguer’s law also leads to satisfactory results. This can be explained by the existing (pseudo-) linearity between the quantities (F_?and A_?) of both theories.-The application of this pH-optode in enzyme sensors for urea and penicillin G results in linear calibration curves, in the case of a fluoresceine based electrode non-linear calibration curves are obtained.