Enhancement of the dynamic range of the measurement of pH using a sensitive layer of methyl red-lophine

This work presents the characterization of a membrane of an indicator dye, methyl red, combined with an imidazole, called lophine, based on different pH values in water. A spectroscopy study was carried out to analyze the pH dependence as a function of the absorbance to varying amounts of methyl red and lophine. This study shows the hyperchromic behavior of the membrane composed of both elements separately and finally, mixed subjected to different pH values. Finally, as an application, the use of this mixture as a coating for a section of optical fiber thinned by chemical attack is proposed.