Fast iron speciation in seawater by catalytic Competitive Ligand Equilibration-Cathodic Stripping Voltammetry with tenfold sample size reduction,Analytica Chimica Acta

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Fast iron speciation in seawater by catalytic Competitive Ligand Equilibration-Cathodic Stripping Voltammetry with tenfold sample size reduction
Analytica Chimica Acta ( IF 5.7 ) Pub Date : 2020-05-01 , DOI: 10.1016/j.aca.2020.04.002
F Sanvito ₁ , D Monticelli ₁

Affiliation

Iron speciation analysis in seawater is a fundamental step to understand the cycling of this element in oceanic waters, in view of its central role in regulating primary productivity and its connection to global planetary cycles. At present, analytical procedures are the bottleneck for speciation analysis, in term of both time and sample size requirement. Here we present a novel instrumental configuration for the speciation analysis of iron by the Competitive Ligand Equilibration - Cathodic Stripping Voltammetry (CLE-CSV) procedure. The new system features a 1 mL microcell and a silver wire pseudoreference enabling a tenfold reduction of the sample volume. 2,3-dihydroxynaphthalene was used as the complexing ligand and atmospheric oxygen as the catalytic enhancer because they ensured the best analytical performances in terms of detection capabilities. The side reaction coefficient for the FeDHN complex αFe'DHN was calibrated against EDTA and an average value of 9.25 for logK'Fe'DHN was calculated. The method was successfully validated in UV digested seawater using diethylenetriaminepentaacetic acid (DTPA), which has known stability constant for iron. The method was lastly applied to six samples from the Ross Sea water column (Antarctica), demonstrating its fit for purpose for the detection of trace amounts of iron ligands in seawater. Thanks to the employed instrumental configuration and the high sensitivity, the proposed method achieved a tenfold reduction in sample size, a tenfold increase in sensitivity compared with other methods employing DHN and halved the analysis time with respect to the fastest method reported in the literature. Half an hour is enough to measure a 12 point titration, making the analysis of at least three titrations per day feasible. It is expected that the application of this procedure will foster the sample throughput, thanks to the reduced analysis time, and make possible the analysis of limitedly available and challenging samples, like porewater and vent fluids via the tenfold reduction in sample size.

中文翻译：

通过催化竞争配体平衡 - 阴极溶出伏安法在海水中快速形成铁，样品尺寸减少十倍

鉴于其在调节初级生产力及其与全球行星循环的联系方面的核心作用，海水中的铁形态分析是了解该元素在海洋中循环的基本步骤。目前，就时间和样本量要求而言，分析程序是形态分析的瓶颈。在这里，我们提出了一种新的仪器配置，用于通过竞争配体平衡 - 阴极溶出伏安法 (CLE-CSV) 程序对铁进行形态分析。新系统具有 1 mL 微量池和银线伪参考，可将样品体积减少 10 倍。2、3-二羟基萘作为络合配体，大气氧作为催化增强剂，因为它们确保了在检测能力方面的最佳分析性能。FeDHN 复合物 αFe'DHN 的副反应系数用 EDTA 校准，计算出 logK'Fe'DHN 的平均值为 9.25。该方法在使用二亚乙基三胺五乙酸 (DTPA) 的紫外线消解海水中成功验证，DTPA 对铁具有已知的稳定常数。该方法最后应用于来自罗斯海水柱（南极洲）的六个样品，证明其适用于检测海水中痕量铁配体的目的。由于采用了仪器配置和高灵敏度，所提出的方法使样本量减少了十倍，与采用 DHN 的其他方法相比，灵敏度提高了 10 倍，并且与文献中报道的最快方法相比，分析时间减少了一半。半小时足以测量 12 点滴定，使每天至少进行 3 次滴定的分析变得可行。由于减少了分析时间，预计该程序的应用将提高样品通量，并通过将样品尺寸减少十倍，使分析有限可用和具有挑战性的样品成为可能，例如孔隙水和通风流体。

更新日期：2020-05-01

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