【作者】 田丽平； 杨莉丽； 魏永巨；

【Author】 TIAN Li-ping,YANG Li-li and WEI Yong-ju~*(College of Chemistry and Material Science,Hebei Normal University, Shijiazhuang 050016)

【机构】 河北师范大学化学与材料科学学院；

【摘要】 研究了咖啡酸的荧光光谱和荧光量子产率。在pH<4.5的酸性条件下,咖啡酸水溶液无荧光;pH 4.5～7.0时,有很弱的荧光;pH>7.0之后,荧光随pH的升高而增强,最大激发波长λ。和发射波长λ。分别为385nm和466nm;pH>8.5之后,荧光强度随pH的升高而下降。咖啡酸的荧光光谱随pH的变化是由于其分子中羧基和羟基质子的离解,用紫外分光光度法测得咖啡酸的电离常数分别为:pK_a1=4.49,pK_a2=7.64,pK_a3=11.21。以硫酸奎宁为参比,测得咖啡酸水溶液的荧光量子产率为0.086。荧光分析法测定的检出限为0.52ng/mL。更多还原

【Abstract】 Fluorescence spectra and fluorescence quantum yield of caffeic acid（CA） have been studied.Under acidic conditions of pH<4.5,CA aqueous solution had no fluorescence.In the pH range of pH 4.5 to 7.0,CA had very weak fluorescence.When pH>7.0,fluorescence increases along with the increase of pH,maximum excitation wavelengthλ_ex and emission wavelengthλ_em were 385 nm and 466 nm,respectively.After pH>8.5,fluorescence decreases along with the increase of pH.The reason of the fluorescence change is because of the ionization of protons of car- boxyl and hydroxyl groups in CA molecule.By an ultraviolet spectrophotometric method,ionization constants of CA were measured to be pK_a1=4.49,pK_a2=7.64 and pK_a3=11.21,respectively.Using quinine bisulphate as a reference, fluorescence quantum yield of CA aqueous solution was measured to be 0.086.The detection limit of spectro-photofluorimetry for the analysis of CA was 0.52 ng/mL.更多还原