Department of Inorganic and Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland.
Anal Chem. 2015 Aug 18;87(16):8084-9. doi: 10.1021/acs.analchem.5b01973. Epub 2015 Aug 4.
We report on a methodology for the direct potentiometric determination of nitrate in seawater by in-line coupling to an electrochemical desalination module. A microfluidic custom-fabricated thin layer flat cell allows one to electrochemically reduce the chloride concentration of seawater more than 100-fold, from 600 mM down to ∼2.8 mM. The desalinator operates by the exhaustive electrochemical plating of the halides from the thin layer sample onto a silver element as silver chloride, which is coupled to the transfer of the counter cations across a permselective ion-exchange membrane to an outer solution. As a consequence of suppressing the major interference of an ion-exchanger based membrane, the 80 μL desalinated sample plug is passed to a potentiometric flow cell of 13 μL volume. The potentiometric sensor is composed of an all-solid-state nitrate selective electrode based on lipophilic carbon nanotubes (f-MWCNTs) as an ion-to-electron transducer (slope of -58.9 mV dec(-1), limit of detection of 5 × 10(-7) M, and response time of 5 s in batch mode) and a miniaturized reference electrode. Nitrate is successfully determined in desalinated seawater using ion chromatography as the reference method. It is anticipated that this concept may form an attractive platform for in situ environmental analysis of a variety of ions that normally suffer from interference by the high saline level of seawater.
我们报告了一种将电化学脱盐模块在线耦合到直接电位测定海水中硝酸盐的方法。微流控定制的薄层平板电池允许我们电化学还原海水中的氯化物浓度超过 100 倍，从 600mM 降低到约 2.8mM。脱盐器通过将卤化物从薄层样品电化学镀在银元素上作为氯化银来操作，这与将抗衡离子通过选择性离子交换膜转移到外部溶液中的转移耦合在一起。由于抑制了基于离子交换剂的膜的主要干扰，80μL 脱盐后的样品塞被传递到 13μL 体积的电位流动池。电位传感器由基于亲脂性碳纳米管 (f-MWCNTs) 的全固态硝酸盐选择性电极组成，作为离子到电子转换器（斜率为-58.9 mV dec(-1)，检测限为 5×10(-7) M，在批量模式下的响应时间为 5s）和一个小型化的参比电极。使用离子色谱法作为参考方法，成功地测定了脱盐海水中的硝酸盐。预计这个概念可能为原位环境分析各种离子提供一个有吸引力的平台，这些离子通常受到海水高盐度的干扰。
