Calibration Free and Fluorescein Based Fiber Optic pH Sensor for Clinical Applications

This communication describes how fluorescein grafted at the end of an optical fiber can be used for calibration free pH sensing in the range of physiological values. The method is based on a complete mathematical description of the fluorescence mechanisms of this pH indicator. The analysis of the shape of the fluorescence spectra allows computing values of both the pH and the pKa₃. Doing this, it becomes possible to access calibration pH sensing using conventional optical fibers. This is, to the best of our knowledge, the first fiber optic calibration free pH sensor reported to date.