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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。
Fluorescence spectroscopy, UV spectroscopy and protonation of Ofloxacin (OFL) under different pH conditions were studied. In strongly acidic solutions, OFL molecules can combine two protons and exist in the form of H3 L2 + triacids with a maximum fluorescence emission wavelength (λmax) of 500 nm. The fluorescence spectra of OFL changed with the increase of pH, and the first fluorescence spots were formed at 35 2 nm in the excitation spectrum and the isochromatic spots appeared in the UV absorption spectrum. This spectral feature indicates that H3 L2 + gradually lost 4 C Carbonyl oxygen bound protons. OFL is present in the form of H2 L + at a pH of 2.5 to 4 with a λmax of 4 to 99 nm. At pH> 4, with the increase of pH, the fluorescence emission peak at 499nm gradually blue-shifted to 455nm, forming a first-order fluorescence emission point at 4 84nm, indicating the dissociation of the C 3 carboxyl proton. At pH 7 or so, OFL exists in the form of bipolar ion HL with λmax of 455 nm, which is the strongest fluorophore. At pH> 8, λmax red shifts from 455nm to about 475nm with the increase of pH, while the fluorescence intensity decreases, indicating that HL loses the protons bound to the piperazine ring N-4. When pH> 10, OFL is in the form of L-anion, fluorescence intensity decreases with increasing pH, but λmax remains unchanged, indicating that the medium environment has an impact on the fluorescence properties of OFL.