铜（II）离子对脱镁叶绿素-a荧光猝灭的研究

本文介绍了一种利用荧光熄灭定量的测定铜（II）的新方法。从新鲜菠菜中提取叶绿素-a，用高氯酸溶液处理，制得脱镁叶绿素-a。测量脱镁叶绿素-a的紫外-可见吸收光谱，观测到505和535nm处有特征吸收峰。在60 ℃水浴中，脱镁叶绿素-a的丙酮溶液与铜（II）离子水溶液混合，5分钟后发现混合液颜色变绿，505和535 nm处吸收峰消失。铜（II）离子水溶液与脱镁叶绿素-a的丙酮溶液混合后发生荧光猝灭现象，而类似浓度的其它生理离子在相同反应条件下对脱镁叶绿素-a的荧光猝灭现象不明显。 研究了铜（II）离子与脱镁叶绿素-a的反应时间，反应温度对荧光强度衰减的影响。并通过阿累尼乌斯经验关系估算铜（II）离子与脱镁叶绿素-a反应的活化能约为10 ±1kJ·mol-1。研究了铜（II）离子的浓度对脱镁叶绿素-a的丙酮溶液荧光强度的影响，在8.0×10-5 ～8.0×10-7 mol·dm-3范围内，铜（II）离子的浓度与混合液的荧光强度成线性衰减关系，检测限可达8.0×10-7 mol·dm-3。利用脱镁叶绿素-a的丙酮溶液的荧光强度变化测量，有望发展成为一种检测铜（II）离子的新方法。

Fluorescence Quenching of Pheophytin‐a by Copper(II) Ions

A method was developed for determination of Cu(II) ions quantitatively by measuring fluorescent intensity of pheophytin‐a (Pheoa) solution. The Pheoa was obtained by de‐intercalation of magnesium from the porphyrin ring of chlorophyll‐a (Chla) extracted from fresh spinach leaves. Its two UV‐Vis absorption peaks at 505 and 535 nm in acetone solution have been observed but disappeared when the acetone solution of Pheoa was mixed with a Cu(II) ion aqueous solution. A fluorescence quenching phenomenon was thus observed when the acetone solution of Pheoa was mixed with an aqueous solution of Cu(II) ions. However, other physiologically relevant cations rarely caused any quenching fluorescence of Pheoa under the same experimental conditions. Kinetics of the fluorescence fading process was investigated by measuring the effects of Cu(II) ion concentration, reaction time and reaction temperature on the fluorescence intensity of the Pheoa acetone solution. An activation energy of (10±1) kJ·mol^?1 was estimated from Arrhenius empirical relation assuming that the interaction between the Pheoa and the Cu(II) ions was the first order reaction. The calibration graph obtained with the fluorescence was linear over the Cu(II) concentration range of 8.0×10^?5?8.0×10^?7 mol·dm^?3 with a detection limit of 8.0×10^?7 mol·dm^?3 for Cu(II) ion.