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研究了伞形花内酯在不同酸度下的荧光光谱,测量了荧光量子产率和电离常数。伞形花内酯有2种荧光型体,分别存在于弱酸性和弱碱性溶液中。在pH 3～6的溶液中,伞形花内酯以中性分子型体存在,最大激发波长λex=325nm,最大发射波长λem=455nm;在pH 9～10.5的溶液中,伞形花内酯主要以阴离子型体存在,λex/λem=367nm/455nm。以硫酸奎宁为参比,测得pH 5.49时分子型体在激发波长325nm的荧光量子产率为0.81,pH 9.49时阴离子型体在激发波长367nm的荧光量子产率为0.91。用pH-荧光法测得7-羟基质子的电离常数pKa=7.61。
Fluorescence spectra of Umbelliferone under different acidities were studied and the fluorescence quantum yield and ionization constant were measured. Umbelliferone has two kinds of fluorescent body, respectively, in weakly acidic and weak alkaline solution. Umbelliferone is present as a neutral molecular species in solution with pH 3-6. The maximum excitation wavelength is λex = 325 nm and the maximum emission wavelength is λem = 455 nm. In the solution with pH 9 ~ 10.5, umbelliferone Mainly in the presence of anionic body, λex / λem = 367nm / 455nm. With quinine sulfate as a reference, the fluorescence quantum yield of the molecular type at pH 5.49 was found to be 0.81 at an excitation wavelength of 325 nm, and the fluorescence quantum yield of the anionic at a wavelength of 367 nm was 0.91 at pH 9.49. The ionization constant of 7-hydroxy protons pKa = 7.61 measured by pH-fluorescence method.