School of Environmental Sciences, University of Liverpool, 4 Brownlow Street, L69 3GP Liverpool, United Kingdom.
Anal Chim Acta. 2012 Oct 9;746:53-62. doi: 10.1016/j.aca.2012.08.013. Epub 2012 Aug 19.
The oxidation potentials of As(0)/As(III) and Sb(0)/Sb(III) on the gold electrode are very close to each other due to their similar chemistry. Arsenic concentration in seawater is low (10-20 nM), Sb occurring at ~0.1 time that of As. Methods are shown here for the electroanalytical speciation of inorganic arsenic and inorganic antimony in seawater using a solid gold microwire electrode. Anodic stripping voltammetry (ASV) and chronopotentiometry (ASC) are used at pH ≤2 and pH 8, using a vibrating gold microwire electrode. Under vibrations, the diffusion layer size at a 5 μm diameter wire is 0.7 μm. The detection limits for the As(III) and Sb(III) are below 0.1 nM using 2 min and 10 min deposition times respectively. As(III) and Sb(III) can be determined in acidic conditions (after addition of hydrazine) or at neutral pH. In the latter case, oxidation of As(0) to As(III) was found to proceed through a transient As(III) species. Adsorption of this species on the gold electrode at potentials where Sb(III) diffused away is used for selective deposition of As(III). Addition of EDTA removes the interfering effect of manganese when analysing As(III). Imposition of a desorption step for Sb(III) analysis is required. Total inorganic arsenic (iAs=As(V)+As(III)) can be determined without interference from Sb nor mono-methyl arsenious acid (MMA) at 1.6<pH<2 using E(dep)=-1 V. Total inorganic antimony (iSb=Sb(V)+Sb(III)) is determined at pH 1 using E(dep)=-1.8 V without interference by As. The methods were tested in samples from the Irish Sea (Liverpool Bay). As(III) was determined on-board ship immediately after sampling. As(III) concentrations were found to range from 0.44 to 1.56 nM and were higher near the coast. Sb(III) was below the detection limit (<0.1 nM Sb(III)), iAs was comprised between 8 and 25 nM while iSb varied from 0.5 to 1.7 nM.
由于砷和锑的化学性质相似，因此它们在金电极上的氧化电位非常接近。海水中的砷浓度较低（10-20 nM），而锑的浓度约为砷的 0.1 倍。本文展示了一种使用固态金微丝电极在海水中对无机砷和无机锑进行电化学形态分析的方法。在 pH 值≤2 和 pH 值 8 下，使用振动金微丝电极进行阳极溶出伏安法（ASV）和计时电位法（ASC）。在振动条件下，直径为 5 μm 的金丝的扩散层尺寸为 0.7 μm。使用 2 分钟和 10 分钟的沉积时间，砷（III）和锑（III）的检测限均低于 0.1 nM。在酸性条件下（加入联氨后）或在中性 pH 值下可以测定砷（III）和锑（III）。在后一种情况下，发现砷（0）氧化为砷（III）是通过一种瞬态砷（III）物种进行的。该物种在锑（III）扩散离开的电位下吸附在金电极上，用于选择性地沉积砷（III）。加入 EDTA 可去除分析砷（III）时锰的干扰影响。分析锑（III）时需要施加一个洗脱步骤。在 1.6<pH<2 时，无需受到锑或单甲基砷酸（MMA）的干扰，即可测定总无机砷（iAs=As(V)+As(III)）。在 pH 值 1 下，使用 E(dep)=-1.8 V 测定总无机锑（iSb=Sb(V)+Sb(III)），而不受砷的干扰。该方法在爱尔兰海（利物浦湾）的样本中进行了测试。在采样后立即在船上测定了砷（III）。发现砷（III）浓度范围为 0.44 至 1.56 nM，在靠近海岸的地方浓度更高。锑（III）低于检测限（<0.1 nM 锑（III）），iAs 介于 8 至 25 nM 之间，而 iSb 则在 0.5 至 1.7 nM 之间变化。
