Crea Pasquale, De Stefano Concetta, Milea Demetrio, Porcino Nunziatina, Sammartano Silvio
Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Università di Messina, Salita Sperone, 31, I-98166 Messina Vill. S. Agata, Italy.
Biophys Chem. 2007 Jul;128(2-3):176-84. doi: 10.1016/j.bpc.2007.04.003. Epub 2007 Apr 20.
The acid base behavior of phytate has been studied (at t=25 degrees C by potentiometry, ISE-H+ glass electrode) in NaNO3aq at different ionic strengths (0.1 < or = I/mol L(-1) < or = 1.0). The interactions with copper(II) were investigated in the same experimental conditions in different metal to ligand (Phy) ratios (1:1 < or = Cu2+ :Phy < or = 4:1), by using both ISE-H+ and ISE-Cu2+ electrodes. Phytate acid base behavior in sodium nitrate is very similar to that in sodium chloride, previously investigated. In the experimental conditions adopted, the formation of three CuiHjPhy(12-2i-j)- species is observed: the mononuclear CuH4Phy6- and CuH5Phy5-, and the dinuclear Cu2H5Phy3-. Analysis of complex formation constants at different ionic strengths reveals that both ISE-H+ and ISE-Cu2+ electrodes gave, within the experimental error, analogous values. Dependence of complex formation constants on ionic strength was modeled by EDH (Extended Debye-Hückel) and SIT (Specific ion Interaction Theory) equations. The sequestering ability of phytate toward copper(II) has been evaluated by the calculation of pL50 (the total ligand concentration, as -log CL, able to bind 50% of metal cation), an empirical parameter already proposed for an objective "quantification" of this ability. A thorough analysis of literature data on phytate-copper(II) complexes has been performed.
在不同离子强度（0.1≤I/mol L⁻¹≤1.0）的硝酸钠水溶液中（于25℃通过电位分析法，采用离子选择性电极-H⁺玻璃电极）研究了植酸的酸碱行为。在相同实验条件下，使用离子选择性电极-H⁺和离子选择性电极-Cu²⁺，以不同的金属与配体（植酸）比例（1:1≤Cu²⁺:Phy≤4:1）研究了其与铜（II）的相互作用。植酸在硝酸钠中的酸碱行为与先前研究的在氯化钠中的酸碱行为非常相似。在所采用的实验条件下，观察到形成了三种CuiHjPhy(12 - 2i - j)-物种：单核的CuH4Phy6⁻和CuH5Phy5⁻，以及双核的Cu2H5Phy3⁻。对不同离子强度下络合物形成常数的分析表明，在实验误差范围内，离子选择性电极-H⁺和离子选择性电极-Cu²⁺给出了类似的值。通过扩展德拜-休克尔（EDH）方程和特定离子相互作用理论（SIT）方程对络合物形成常数与离子强度的依赖性进行了建模。通过计算pL50（能够结合50%金属阳离子的总配体浓度，以-log CL表示）评估了植酸对铜（II）的螯合能力，pL50是一个已被提出用于客观“量化”这种能力的经验参数。对有关植酸-铜（II）络合物的文献数据进行了全面分析。
