A ratiometric fluorescent pH glass optode based on a boron-dipyrromethene derivative

This paper describes the preparation of a single-excitation, dual-emission type optical pH-sensing device using a newly designed proton-responsive boron-dipyrromethene derivative (KBH-01). The indicator dye was successfully synthesized and immobilized covalently on the surface of a porous glass support (Corning 7930, 13 mm × 30 mm size with a thickness of 1 mm) having a large internal surface area (250 m²/g) using a silane-coupling agent. The resulting pH glass optode shows dual fluorescence emission in aqueous buffer solutions of varying pH values, allowing ratiometric signal processing. The response curves are independent of buffer ionic strength. The sensor response was found to be reversible in the pH range from below 0.8 to 4.5 and showed good repeatability. The determination of pH of gastric juice samples was demonstrated as a possible practical application of the pH glass optode. The pH values determined by the pH glass optode corresponded reasonably to those measured by a field effect transistor (FET) pH meter. These results indicate that the novel pH glass optode can be employed as a pH-sensing device with high durability, sensitivity and accuracy for medical and environmental analyses.