The relevance of ligand exchange kinetics in the measurement of iron speciation by CLE–AdCSV in seawater
The relevance of ligand exchange kinetics in the measurement of iron speciation by CLE–AdCSV in seawater
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配体交换动力学与 CLE-AdCSV 测量海水中铁形态的相关性
DOI：
10.1016/j.marchem.2014.09.005
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发表时间：
2015
期刊：
影响因子：
3
通讯作者：
M. Filella
中科院分区：
文献类型：
--
作者：
L. M. Laglera;M. Filella
CLE-AdCSV（竞争性配体交换-吸附阴极溶出伏安法）已被证明是认识有机物在调节水生态系统中铁的生物地球化学循环中所起的关键作用的决定性技术。由于该方法需要在进行测量之前溶液的所有组分之间的平衡，因此进行配体交换的动力学的准确知识是必不可少的。该过程的动力学最常被描述为解离（或Eigen-Wilkins）机制，一些作者甚至声称，在这种方法下，铁络合物在CLE过程中解离得如此缓慢，以至于该方法将无效。的过程的复杂性，大大超过了简单的本征-威尔金斯机制的机械描述的基础上，讨论了广泛的概述可能的反应路线。天然沃茨的基质成分的作用的证据和不可能的出口动力学常数的系统，其特征在于不同的分子力学，在以前的研究中大多被忽视，被强调。从各种方法学途径获得的实验证据允许推断CLE-AdCSV测量中应用的CLE平衡时间的范围，并进一步证明本征-威尔金斯机制只是适用于天然沃茨的许多反应途径之一。建议在设计任何使用CLE-AdCSV的实验之前，研究铁CLE机制。
CLE–AdCSV (competitive ligand exchange–adsorptive cathodic stripping voltammetry) has proved to be a decisive technique in recognising the key role that organic matter plays in modulating the biogeochemical cycle of iron in aquatic ecosystems. As the method requires equilibrium among all the constituents of the solution before measurements are taken, accurate knowledge of the kinetics of the undergoing ligand exchange is essential. The kinetics of the process has been most frequently described in terms of a dissociative (or Eigen–Wilkins) mechanism, with some authors even claiming that, under such approach, iron complexes would dissociate during CLE so slowly that the method would be invalidated. The complexity of the processes—largely exceeding the simple mechanistic description of the Eigen–Wilkins mechanism—is discussed on the basis of a broad overview of possible reaction routes. Evidence of the role of matrix components of natural waters is presented and the impossibility of exporting kinetic constants to systems characterised by different molecular mechanics, mostly ignored in previous studies, is highlighted. Experimental evidence obtained from various methodological approaches allows inferring the range of CLE equilibration times to be applied in CLE–AdCSV measurements and further proves that the Eigen–Wilkins mechanism is just one of the many reaction routes applicable in natural waters. Studying iron CLE mechanisms for proposed competing ligands before designing any experiment using CLE–AdCSV is recommended.