Abstract Despite arsenite can be reduced to As(0) and deposited at the surface of solid electrodes such as gold, platinum, or copper, it cannot form amalgams with mercury, and so the addition of other metal ions is required for its deposition. In this manuscript, mechanistic analysis of the cathodic stripping square-wave voltammetric response of the system copper‑arsenic is presented. For the analysis of experimental responses, a mathematical model is used to consider that a surface-active reagent undergoes a charge transfer step followed by a chemical reaction. The dependences of the differential peak current, and the respective peak potential and half-peak width on the square-wave frequency were used to estimate the apparent stability constant of arsenide formation and that the electrode reaction would involve the direct transfer of 2 electrons, while the simulation and fit of forward and backward voltammetric responses have been useful for inferring other parameters such as the formal charge transfer rate constant of the global electron transfer reaction, a pseudo-first order homogeneous rate constant associated with arsenide formation, and the charge transfer coefficient of the global electron transfer reaction. Besides the values estimated for each of those parameters, all simulations indicate that the reduction of copper instead of arsenic would be taking place during the cathodic stripping scan. Accordingly, the trace-analysis reaction of arsenic in the presence of copper would be based on the surface accumulation of a metal complex, where Cu2+ would be the metal cation and an arsenide species the ligand. The stability of that complex at the surface of a mercury electrode would depend not only on the applied potential, but also on the ratio between copper, arsenic, and protons.

中文翻译：

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铜砷系统在汞电极上阴极溶出方波伏安响应的机理分析

摘要 尽管亚砷酸盐可以被还原为As(0)并沉积在金、铂或铜等固体电极的表面，但它不能与汞形成汞齐，因此需要加入其他金属离子才能沉积。在这份手稿中，介绍了系统铜砷的阴极剥离方波伏安响应的机械分析。对于实验响应的分析，使用数学模型来考虑表面活性试剂经历电荷转移步骤，然后是化学反应。差分峰值电流的相关性以及各自的峰值电位和半峰宽对方波频率的依赖性被用来估计砷化物形成的表观稳定常数，并且电极反应将涉及 2 个电子的直接转移，而正向和反向伏安响应的模拟和拟合有助于推断其他参数，例如全局电子转移反应的正式电荷转移速率常数、与砷化物形成相关的伪一级均匀速率常数以及电荷转移全局电子转移反应系数。除了为这些参数中的每一个估计的值之外，所有模拟都表明在阴极剥离扫描期间将发生铜而不是砷的还原。因此，在铜存在下砷的痕量分析反应将基于金属络合物的表面积累，其中 Cu2+ 将是金属阳离子，而砷化物则是配体。