Departament de Química. Universitat de Lleida and AGROTECNIO, Rovira Roure 191, 25198, Lleida, Spain.
Departament de Química. Universitat de Lleida and AGROTECNIO, Rovira Roure 191, 25198, Lleida, Spain.
Anal Chim Acta. 2018 Dec 4;1035:32-43. doi: 10.1016/j.aca.2018.06.071. Epub 2018 Jun 27.
Four analytical techniques are compared: AGNES (Absence of Gradients and Nernstian Equilibrium Stripping), LASV (Anodic Stripping Voltammetry with Linear stripping), DGT (Diffusive Gradients in Thin films) and PIM (Polymer Inclusion Membranes). These techniques have been designed to provide the free ion concentration or a labile fraction, complementarily contributing to an integrated description of speciation and availability. Their simultaneous application to the determination of free Zn concentrations or labile fluxes in seven solutions of a hydroponic medium reveals characteristics of each technique and correlations between their results. All dynamic results can be interpreted in terms of a general theoretical framework on fluxes. Indeed, in techniques under diffusion-limited conditions in the sample, the flux can be split into the free contribution (linearly proportional to the free fraction), plus the contribution of the complexes (where mobility, lability and abundance of complexation are intertwined). A methodology to compute lability degrees is developed. Measurements with PIM devices confirm that diffusion in the sample solution is not rate limiting, so its flux is proportional to the free metal in the donor solution. A proportionality between the responses of any given two techniques is observed, which suggests that, for the low ligand-to-metal concentration ratios used in the present work, any of these techniques would correlate similarly with uptake, toxic or nutritional measurements.
AGNES（无梯度和能斯特平衡剥离）、LASV（线性 stripping 阳极溶出伏安法）、DGT（薄膜中的扩散梯度）和 PIM（聚合物包容膜）。这些技术旨在提供游离离子浓度或不稳定分数，为形态和可用性的综合描述提供补充。将它们同时应用于确定水培介质中七种溶液中的游离 Zn 浓度或不稳定通量，揭示了每种技术的特点以及它们的结果之间的相关性。所有动态结果都可以根据通量的一般理论框架进行解释。实际上，在样品中扩散受限条件下的技术中，通量可以分为游离贡献（与游离分数成正比），加上配合物的贡献（其中配合物的迁移率、不稳定性和丰度交织在一起）。开发了一种计算不稳定性程度的方法。使用 PIM 设备进行的测量证实，样品溶液中的扩散不是限速步骤，因此其通量与供体溶液中的游离金属成正比。观察到任何给定两种技术之间的响应之间存在比例关系，这表明在本工作中使用的低配体与金属浓度比下，这些技术中的任何一种都可以与摄取、毒性或营养测量类似地相关。
