Department of Inorganic and Analytical Chemistry , University of Geneva , Quai Ernest-Ansermet 30 , CH-1211 Geneva , Switzerland.
Idronaut , Via Monte Amiata 10 , I-20047 Brugherio (Milano) , Italy.
Anal Chem. 2018 Apr 3;90(7):4702-4710. doi: 10.1021/acs.analchem.7b05299. Epub 2018 Mar 19.
A new submersible probe for the in situ detection of nitrate, nitrite, and chloride in seawater is presented. Inline coupling of a desalination unit, an acidification unit, and a sensing flow cell containing all-solid-state membrane electrodes allows for the potentiometric detection of nitrate and nitrite after removal of the key interfering ions in seawater, chloride and hydroxide. Thus, the electrodes exhibited attractive analytical performances for the potentiometric detection of nitrate and nitrite in desalinated and acidified seawater: fast response time ( t < 12 s), excellent stability (long-term drifts of <0.5 mV h), good reproducibility (calibration parameter deviation of <3%), and satisfactory accuracy (uncertainties <8%Diff compared to reference technique). The desalination cell, which can be repetitively used for about 30 times, may additionally be used as an exhaustive, and therefore calibration-free, electrochemical sensor for chloride and indirect salinity detection. The detection of these two parameters together with nitrate and nitrite may be useful for the correlation of relative changes in macronutrient levels with salinity cycles, which is of special interest in recessed coastal water bodies. The system is capable of autonomous operation during deployment, with routines for repetitive measurements (every 2 h), data storage and management, and computer visualization of the data in real time. In situ temporal profiles observed in the Arcachon Bay (France) showed valuable environmental information concerning tide-dependent cycles of nitrate and chloride levels in the lagoon, which are here observed for the first time using direct in situ measurements. The submersible probe based on membrane electrodes presented herein may facilitate the study of biogeochemical processes occurring in marine ecosystems by the direct monitoring of nitrate and nitrite levels, which are key chemical targets in coastal waters.
一种用于原位检测海水中硝酸盐、亚硝酸盐和氯离子的新型潜水探测器。脱盐单元、酸化单元和包含全固态膜电极的传感流动池的在线偶联允许在去除海水中关键干扰离子（氯离子和氢氧根离子）后，对硝酸盐和亚硝酸盐进行电位检测。因此，这些电极在脱盐和酸化海水中对硝酸盐和亚硝酸盐的电位检测表现出了有吸引力的分析性能：快速响应时间（<12s）、出色的稳定性（长期漂移<0.5mVh）、良好的重现性（校准参数偏差<3%）和令人满意的准确性（与参考技术相比，不确定度<8%Diff）。脱盐池可重复使用约 30 次，也可用作氯离子的完全（因此无需校准）电化学传感器和间接盐度检测。同时检测这两个参数以及硝酸盐和亚硝酸盐可能有助于将营养盐水平的相对变化与盐度循环相关联，这在凹陷沿海水体中特别重要。该系统在部署期间能够自主运行，具有重复测量（每 2 小时一次）、数据存储和管理以及实时计算机可视化数据的例程。在法国阿卡雄湾（Arcachon Bay）观察到的原位时间剖面提供了有关泻湖硝酸盐和氯离子水平与潮汐相关循环的有价值的环境信息，这是首次使用直接原位测量来观察这些信息。本文介绍的基于膜电极的潜水探测器可通过直接监测沿海水域的关键化学目标硝酸盐和亚硝酸盐水平，促进对海洋生态系统中生物地球化学过程的研究。
