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对二氟沙星在中性水溶液中的光化学性质进行了研究.在pH值为7.17的水溶液中二氟沙星的紫外吸收峰位于273 nm(摩尔消光系数ε=33000 dm3·mol-1·cm-1),323 nm(ε=15500 dm3·mol-1·cm-1),335 nm(ε=15500 dm3·mol-1·cm-1)处.荧光吸收和发射光谱均显示二氟沙星具有pH效应,其pKa(电离平衡常数)测定分别为5.9和9.8.二氟沙星的荧光量子产额较低,在pH=3.00时达到最大值,为0.06.同时对二氟沙星在中性水溶液中的激光光解和脉冲辐解进行详细研究.激光光解研究发现在水溶液中二氟沙星的三重激发态位于620nm,其摩尔消光系数为7900 dm3·mol-1·cm-1.通过能量转移的方法得到其三重激发态的能量为263.5 kJ·mol-1,三重激发态的量子产额为0.21.在激光激发下,二氟沙星进行单光子电离其量子产额为0.02.脉冲辐解研究表明二氟沙星可以与水合电子(e-aq)及羟基自由基(·OH)快速反应,其二级反应动力学常数分别为1.72×1010和1.0×1010dm3·mol-1·s-1.本文对二氟沙星光化学性质的研究有助于确定其光敏毒性的产生机理.
The photochemical properties of difloxacin in neutral aqueous solution were studied. The UV absorption peak of difloxacin at pH7.17 was 273 nm (molar extinction coefficient ε = 33000 dm3 · mol-1 · cm -1), 323 nm (ε = 15500 dm3 · mol-1 · cm-1) and 335 nm (ε = 15500 dm3 · mol-1 · cm-1) respectively.Fluorescein absorption and emission spectra showed that difloxacin Has a pKa (ionization equilibrium constant) of 5.9 and 9.8, respectively, as measured by the pH effect.The fluorescence quantum yield of difloxacin is relatively low, reaching a maximum of 0.06 at pH = 3.00, Laser photolysis and pulsed radiolysis in aqueous solution were studied in detail.It was found by laser photolysis that the triplet excited state of difloxacin was at 620 nm and its molar extinction coefficient was 7900 dm3 · mol-1 · cm-1. The energy of triplet excited state was 263.5 kJ · mol-1 by energy transfer method, and the quantum yield of triplet excited state was 0.21. The quantum yield of difloxacin by single photon ionization was 0.02 under laser excitation. Pulsed radiolysis studies showed that difloxacin can rapidly react with hydrated electron (-eq) and hydroxyl radical (· OH), the second-order kinetic constants are 1 .72 × 1010 and 1.0 × 1010dm3 · mol-1 · s-1. The study of the photochemical properties of difloxacin will help determine the mechanism of phototoxicity.