A NOVEL FIBEROPTIC PH SENSOR INCORPORATING CARBOXY SNAFL-2 AND FLUORESCENT WAVELENGTH-RATIOMETRIC DETECTION

A fiber-optic pH sensor was prepared using the self-referencing fluore scent pH probe carboxy seminaphthofluorescein (SNAFL-2). The ratio of the emission from the base form of this dye and the emission near the isoemissive point is insensitive to variations in the excitation inten sity and photobleaching. The carboxy SNAFL-2 and a photoaffinity cross linker, 4-azido-2,3,5,6-tetrafluorobenzoic acid, succinimidyl ester, w ere attached onto poly(acrylamide-covinylamine) to form a hydrophilic functional membrane for the fiber-optic sensor. Photo crosslinking was used to create crosslinked pH-sensing membrane and covalently bind th e membrane onto the surface of the PMMA optical fiber. The fluorescent properties of the membrane-fiber conjugate have been determined. The membrane is stable, and the pH sensor shows a fast response time and e xcellent resolution in a wide pH range of 3 to 11. (C) 1998 John Wiley & Sons, Inc.