Chung K H, Lee W, Cho Y H, Choi G S, Lee C W
Nuclear Environment Research Division, Korea Atomic Energy Research Institute, 150 Dukjin-Dong, Yuseong-Gu, Daejeon 305-353, South Korea.
Talanta. 2005 Jan 30;65(2):389-95. doi: 10.1016/j.talanta.2004.06.026.
The complexation of europium ion (Eu(III)) with a soil fulvic acid (FA) has been studied at pH 5 in 0.01M NaClO(4) by different experimental methods, i.e. synchronous fluorescence spectroscopy (SyFS) and time resolved laser-induced fluorescence spectroscopy (TRLFS). A series of SyFS quenching spectra was obtained by increasing the Eu(III) concentration and keeping the FA concentration constant. The emission spectra and fluorescence lifetimes of the Eu(III) bound to the FA were also measured by a TRLFS system using the same solution used in the SyFS spectral measurement. From the analysis of the fluorescence data obtained by the SyFS and the TRLFS using a non-linear least-squares method, the concentration of the binding sites (C(L)) of the FA accessible for the Eu(III) and the corresponding conditional stability constants (logK) were estimated. The two different methods gave rise to constants being comparable with one another. The logK and C(L) values (mean +/- standard deviation of three determinations) determined by the SyFS were 6.4 +/- 0.2 (6.7 +/- 0.1mumolL(-1): by the TRLFS) and 10 +/- 1mumolL(-1) (7 +/- 1mumolL(-1): by the TRLFS), respectively. The applicability of the FA fluorescence quenching techniques for estimating the europium binding parameters was proved by the direct monitoring of the Eu(III) bound to the FA using the TRLFS system.
采用不同的实验方法，即同步荧光光谱法（SyFS）和时间分辨激光诱导荧光光谱法（TRLFS），研究了在pH值为5的0.01M高氯酸钠（NaClO₄）溶液中铕离子（Eu(III)）与土壤富里酸（FA）的络合作用。通过增加Eu(III)浓度并保持FA浓度恒定，获得了一系列SyFS猝灭光谱。还使用与SyFS光谱测量相同的溶液，通过TRLFS系统测量了与FA结合的Eu(III)的发射光谱和荧光寿命。通过使用非线性最小二乘法对SyFS和TRLFS获得的荧光数据进行分析，估算了FA中可被Eu(III)利用的结合位点浓度（C(L)）和相应的条件稳定常数（logK）。两种不同方法得到的常数相互可比。SyFS测定的logK和C(L)值（三次测定的平均值±标准差）分别为6.4±0.2（TRLFS为6.7±0.1μmolL⁻¹）和10±1μmolL⁻¹（TRLFS为7±1μmolL⁻¹）。通过使用TRLFS系统直接监测与FA结合的Eu(III)，证明了FA荧光猝灭技术在估算铕结合参数方面的适用性。
