The aim of this study was to develop an analytical method to determine free concentrations of Europium (Eu(III)) in natural waters. Europium(III) in solution was detected using cathodic stripping voltammetry after complexation with N-nitroso-N-phenylhydroxylamine (cupferron). Optimization of analytical parameters allowed us to detect nanomolar levels of Eu(III) in solution. Free Eu(III) in solution was measured using the Donnan membrane technique in which a natural solution (the “donor”, containing various ligands) is separated from a ligand-free solution (the “acceptor”) by a cation-exchange membrane. This membrane allows only non-colloidal cationic species to pass through it, and after an adequate time equilibrium is reached between both compartments. Total Eu(III) concentration can then be quantified in the acceptor solution and related to free Eu(III) in the natural sample. Due to its high valency, free Eu(III) tends to adsorb strongly to the cation-exchange membrane. In order to determine the physicochemical conditions minimizing this adsorption, we analyzed solutions of different Eu(III) and Ca(II) (as background ion) concentrations. Results showed that 100 mM of Ca(II) were necessary to make adsorption of Eu(III) onto the membrane negligible. The optimized setup was then used to quantify Eu(III) complexation in a Eu(III)-dissolved organic matter solution.

本研究的目的是开发一种分析方法来测定天然水中游离铕 (Eu(III)) 的浓度。与N-亚硝基-N-苯基羟胺 (cupferron)络合后，使用阴极溶出伏安法检测溶液中的铕 (III) 。分析参数的优化使我们能够检测溶液中纳摩尔水平的 Eu(III)。使用唐南膜技术测量溶液中的游离 Eu(III)，其中通过阳离子交换膜将天然溶液（“供体”，含有各种配体）与不含配体的溶液（“受体”）分离。该膜仅允许非胶体阳离子物质通过，并且在足够的时间后两个隔室之间达到平衡。然后可以对受体溶液中的总 Eu(III) 浓度进行定量，并与天然样品中的游离 Eu(III) 相关。由于其高价态，游离的 Eu(III) 往往会强烈吸附到阳离子交换膜上。为了确定使这种吸附最小化的物理化学条件，我们分析了不同浓度的 Eu(III) 和 Ca(II)（作为背景离子）的溶液。结果表明，需要 100 mM Ca(II) 才能使膜上的 Eu(III) 吸附忽略不计。然后使用优化的设置来量化溶解了 Eu(III) 的有机物溶液中的 Eu(III) 络合。