论文部分内容阅读
研究了环丙沙星(ciprofloxacin,CIP)在不同pH条件下的荧光光谱、紫外吸收光谱和质子化作用,测量了CIP在中性条件下的荧光量子产率。在H+浓度大于1mol·L-1的HCl介质中,CIP分子(简写为HL)可以结合3个质子而以H4L3+形式存在,有微弱的荧光,最大荧光发射波长(λmax)为456nm。在pH0～2的酸性条件下,CIP主要以H3L2+形式存在,λmax为450nm,荧光较弱,荧光强度随pH的升高而上升。在pH2～4时,CIP主要以H2L+形式存在,具有强荧光,λmax仍为450nm。当pH>4时,λmax逐步蓝移到414nm,荧光强度随pH的升高而稍有降低,同时紫外吸收光谱也有明显变化,表明H2L+随pH升高而失去质子,以双极离子HL形式存在。当pH>8时,荧光强度随pH升高而减弱至消失,表明HL逐步失去质子,转化为无荧光的阴离子L-。在分子形态变化过程中,最大荧光激发波长始终在275nm附近,但最大荧光发射波长有较大变化。在pH7.0的缓冲溶液中,以硫酸奎宁为参比,测得CIP在最大荧光激发波长275nm处的荧光量子产率为0.12。
Fluorescence spectra, UV absorption spectra and protonation of ciprofloxacin (CIP) under different pH conditions were studied. The fluorescence quantum yield of CIP under neutral condition was measured. In HCl medium with H + concentration greater than 1 mol·L-1, CIP molecule (abbreviated as HL) can exist as H4L3 + in combination with three protons with weak fluorescence and the maximum fluorescence emission wavelength (λmax) is 456 nm. Under the acidic conditions of pH0 ~ 2, CIP mainly exists in the form of H3L2 +, the λmax is 450nm, the fluorescence is weak, and the fluorescence intensity increases with the increase of pH. At pH2 ~ 4, CIP mainly exists in the form of H2L +, with strong fluorescence, λmax is still 450nm. When pH> 4, λmax gradually blue shifted to 414nm, the fluorescence intensity decreased slightly with the increase of pH, and the UV absorption spectra also changed obviously, indicating that H2L + lost its proton with the increase of pH and existed as bipolar ion HL . When pH> 8, the fluorescence intensity decreases with the increase of pH and disappears, indicating that HL gradually loses protons and converts to non-fluorescent anions L-. In the process of molecular morphological changes, the maximum fluorescence excitation wavelength is always around 275nm, but the maximum fluorescence emission wavelength has a larger change. The fluorescence quantum yield of CIP at the maximum fluorescence excitation wavelength of 275 nm was 0.12 in the buffer solution of pH7.0 with quinine sulfate as a reference.