A Comparison between Four Analytical Methods for the Measurement of Fe(II) at Nanomolar Concentrations in Coastal Seawater
A Comparison between Four Analytical Methods for the Measurement of Fe(II) at Nanomolar Concentrations in Coastal Seawater
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DOI：
10.3389/fmars.2017.00192
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发表时间：
2017-01-01
影响因子：
3.7
通讯作者：
Milne, Angela
中科院分区：
文献类型：
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作者：
Hopwood, Mark J.;Birchill, Antony J.;Milne, Angela
海水中溶解的Fe（II）被认为是微生物的重要微量营养素，但由于其瞬时性质，其分析具有挑战性。我们进行了一系列的Fe（II）的方法比较实验，其中5至31 nM的Fe（II）的穗被添加到不同的溶解氧（37至156 μ M）浓度的操纵海水。比较了四种分析方法观察到的Fe（II）浓度：亚铁嗪分光光度法、溶出伏安法和使用鲁米诺的流动注射分析（有和没有预浓缩柱）。不同方法之间的直接比较是从推导出的表观Fe（II）氧化速率常数（k（1））。虽然两种基于鲁米诺的方法在整个实验中产生最相似的浓度，但它们之间的k（1）仍然存在20-30%的差异。促成因素可能包括校准曲线中的不确定性，以及对Co（II）和腐殖酸/富里酸有机物质干扰的不同反应。在加入Fe（II）加标物后10 min-2 h，鲁米诺法和亚铁嗪法之间测量的Fe（II）浓度的差异在绝对值（>4 nM）和相对于加入的加标物（>初始Fe（II）浓度的20%）方面总是相对较大。由Fe（Ⅱ）浓度测定的k（1）分别是由鲁米诺测定的Fe（Ⅱ）浓度的3- 80%和4- 16%。在添加腐殖/灰黄质材料以将溶解性有机碳提高到120 μ M后，发现k（1）的可比性最差。一种没有预浓缩的鲁米诺方法，然后观察到Fe（II）下降到检测限以下（
Dissolved Fe(II) in seawater is deemed an important micronutrient for microbial organisms, but its analysis is challenging due to its transient nature. We conducted a series of Fe(II) method comparison experiments, where spikes of 5 to 31 nM Fe(II) were added to manipulated seawaters with varying dissolved oxygen (37 to 156 mu M) concentrations. The observed Fe(II) concentrations from four analytical methods were compared: spectrophotometry with ferrozine, stripping voltammetry, and flow injection analysis using luminol (with, and without, a pre-concentration column). Direct comparisons between the different methods were undertaken from the derived apparent Fe(II) oxidation rate constant (k(1)). Whilst the two luminol based methods produced the most similar concentrations throughout the experiments, k(1) was still subject to a 20-30% discrepancy between them. Contributing factors may have included uncertainty in the calibration curves, and different responses to interferences from Co(II) and humic/fulvic organic material. The difference in measured Fe(II) concentrations between the luminol and ferrozine methods, from 10 min-2 h after the Fe(II) spikes were added, was always relatively large in absolute terms (>4 nM) and relative to the spike added ( >20% of the initial Fe(II) concentration). k(1) derived from ferrozine observed Fe(II) concentrations was 3-80%, and 4-16%, of that derived from luminol observed Fe(II) with, and without, pre concentration respectively. The poorest comparability of k(1) was found after humic/fulvic material was added to raise dissolved organic carbon to 120 mu M. A luminol method without pre-concentration then observed Fe(II) to fall below the detection limit (