氧氟沙星的荧光光谱与质子化作用研究

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Abstract Fluorescence spectra, ultraviolet spectra and protonation of Ofloxacin (OFL) at different pH values have been studied. In strong acidic solutions, OFL molecule might accept two protons to exist as ternary acid H₃L²⁺ with a maximum emission wavelength (λ_max) at 505 nm. Along with the increase in pH value, fluorescence spectrum of OFL changed, an iso-fluorescence point at 352 nm was found in the fluorescence excitation spectra, and at the same time, isosbestic points were found in its UV absorption spectra. This spectral feature reveals that H₃L²⁺ gradually lost hydrogen ion combined on C-4 keto oxygen. In the range of pH 2.5 to pH 4, OFL exists as H₂L⁺ with λ_max at 499 nm. When pH＞4, the fluorescence emission peak at 499 nm gradually blue-shifted to 455 nm as pH was increasing, and an iso-fluorescence emission point was formed at 484 nm，indicating the dissociation of hydrogen ion of carboxylic acid at C-3. At about pH 7.0, OFL exists in the dipole ion form HL with λ_max at 455 nm, which is the strongest fluorescence form. When pH＞8, λ_max red-shift from 455 to 475 nm as pH increases, meanwhile, fluorescence intensity decreases, indicating that HL lost hydrogen ion combined on N-4 of piperazinyl group. When pH＞10, OFL exists in anion ion form L^-，and fluorescence intensity decreases with pH increasing, but λ_max remains essentially constant, indicating that medium environment influences the fluorescence property of OFL.

Key words：Ofloxacin;Quinolone;Fluorescence spectrum;Ultraviolet spectrum;Protonation

Received: 2004-02-26 Accepted: 2004-06-28

ZTFLH:

O657.3

Corresponding Authors: XU Yi-zhuang

Cite this article:

LIU Cui-ge,XU Yi-zhuang,WEI Yong-ju, et al. Fluorescence Spectra and Protonation of Ofloxacin [J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2005, 25(04): 584-587.

URL:

https://www.gpxygpfx.com/EN/Y2005/V25/I04/584