【摘要】 研究了氧氟沙星(Ofloxacin ,OFL)在不同pH条件下的荧光光谱、紫外光谱和质子化作用。在强酸性溶液中,OFL分子可以结合两个质子而以三元酸H3 L2 + 的形式存在,最大荧光发射波长(λmax)为5 0 5nm。随着pH值升高,OFL的荧光光谱发生变化,在激发光谱中35 2nm形成一等荧光点,同时在紫外吸收光谱中出现等色点,这一光谱特征表明H3 L2 + 逐渐失去4位C羰基氧结合的质子。在pH 2 . 5～4范围内,OFL以H2 L+ 形式存在,λmax为4 99nm。当pH >4时,随pH值升高,位于4 99nm的荧光发射峰逐渐蓝移至4 5 5nm ,在4 84nm形成一等荧光发射点,表明C 3位羧基质子的离解。在pH 7左右,OFL以双极离子HL形式存在,λmax为4 5 5nm ,是最强的荧光型体。当pH >8时,随pH值升高,λmax由4 5 5nm红移至约4 75nm ,同时荧光强度下降,表明HL失去哌嗪环N -4上结合的质子。当pH >10时,OFL以阴离子L-形式存在,荧光强度随pH值升高而降低,但λmax基本不变,表明介质环境对OFL的荧光性质有一定影响。更多还原

【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 H 3L 2+ 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 H 3L 2+ gradually lost hydrogen ion combined on C-4 keto oxygen. In the range of pH 2.5 to pH 4, OFL exists as H 2L + 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.更多还原