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DIBUCAINE FLUORESCENCE and LIFETIME IN AQUEOUS MEDIA AS A FUNCTION OF pH*
Author(s) -
Vanderkooi Garret
Publication year - 1984
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1984.tb08855.x
Subject(s) - chemistry , fluorescence , titration , absorption (acoustics) , aqueous solution , dibucaine , quinoline , aromatic amine , analytical chemistry (journal) , tertiary amine , amine gas treating , photochemistry , quenching (fluorescence) , absorption spectroscopy , inorganic chemistry , chromatography , organic chemistry , physics , quantum mechanics , acoustics
— The absorption and fluorescence spectra and fluorescence lifetimes of the local anesthetic dibucaine (2‐butoxy‐N‐[2‐(diethylamino) ethyl]‐4‐quinoline carboxamide) are reported as a function of pH in aqueous media. The fluorescence emission maxima are at 400 nm in neutral solution, 397 nm in alkali, and 454 nm in acid. The fluorescence is strongest and has the longest lifetime in neutral solution; the quantum yields are 0.25, 0.033, and 0.032, and the lifetimes (determined by the phase shift method) are 3.29, 0.60, and 1.37 ns, for the neutral, alkaline, and acid solutions, respectively. The pKoi the tertiary amine group was determined by fluorescence intensity and lifetime measurements to be 8.95, and the pK of the aromatic nitrogen was found to be 1.80 ± 0.03 by absorption and fluorescence intensity measurements. Phase and modulation lifetimes differed in the manner expected for a two lifetime system in the pH titration range of the tertiary amine, but gave anomalous results in the titration range of the aromatic nitrogen.