Modeling of fiber optic-based pH sensors

Luis H. Garcia-Rubio; Sylvia H. Chang

doi:10.1117/12.170658

10 March 1994 Modeling of fiber optic-based pH sensors

Luis H. Garcia-Rubio, Sylvia H. Chang

Proceedings Volume 2068, Chemical, Biochemical, and Environmental Fiber Sensors V; (1994) https://doi.org/10.1117/12.170658
Event: Optical Tools for Manufacturing and Advanced Automation, 1993, Boston, MA, United States

Abstract

The fiber-optic-based pH sensors have many advantages over the traditional pH electrodes. They are rigid, self-calibrating, and show negligible drift. In addition, they are capable of detecting pH changes with a precision of 0.001 pH units. These features make fiber optic pH sensors especially suitable for on-line industrial applications. The pH sensor consists of an indicator dye immobilized in a polymer matrix. The pH of the solution is related to the relative fraction of the protonated and the dissociated species of the dye, whose absorption spectrum changes according to the pH of the surroundings. The response of the sensor is determined by the dissociation equilibrium of the immobilized dye and its interaction with the polymer matrix. In order to have meaningful pH measurements it is important to understand the sensing mechanisms and the corresponding absorption spectra. In this paper a model is reported for the chemical reaction taking place within the membrane during the course of pH measurements. The model takes into consideration the interaction between the indicator dye and the membrane and identifies the key parameters to be used in the design of membranes for pH sensing. In addition, the absorption spectra of the dye in solution are deconvoluted and analyzed for reference purposes.

Citation Download Citation

Luis H. Garcia-Rubio and Sylvia H. Chang "Modeling of fiber optic-based pH sensors", Proc. SPIE 2068, Chemical, Biochemical, and Environmental Fiber Sensors V, (10 March 1994); https://doi.org/10.1117/12.170658

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