School of Chemistry and Materials Science, Ludong University, Yantai, 264025, Shandong, PR China; Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), Shandong Provincial Key Laboratory of Coastal Environmental Processes, YICCAS, Yantai, Shandong, 264003, PR China.
School of Chemistry and Materials Science, Ludong University, Yantai, 264025, Shandong, PR China.
Anal Chim Acta. 2020 Sep 8;1129:136-142. doi: 10.1016/j.aca.2020.07.019. Epub 2020 Jul 23.
Traditional potentiometric NO-selective electrodes suffer from a fundamental limitation of the Nernst slope (59.1 mV/dec at 25 °C) due to the relationship between the potential and the logarithmic of ionic activity. Herein, a coulometric signal readout is proposed instead of the potentiometric response for detection of NO based on an ordered mesoporous carbon (OMC)-based solid-contact ion-selective electrode (ISE). The mechanism for obtaining the coulometric signal is based on the electrical double layer capacitance of OMC compensating the potential change at the ion-selective membrane/solution interface during the measurements under the control of a constant applied potential. Under the optimized conditions, the coulometric signal for the OMC-based solid-contact NO-ISE shows two linear responses in the activity range of 1.0 × 10-8.0 × 10 M and 8.0 × 10-8.0 × 10 M, and the detection limit is 4.0 × 10 M (3σ/s). The proposed coulometric response also shows excellent reproducibility and stability in the presence of O and CO and light on/off. Additionally, the coulometric response shows acceptable and reliable results for detection of NO in mineral water as compared to the traditional potentiometric response and the ion chromatography. This work provides a promising alternative signal readout for detection of ions by using solid-contact ion-selective electrodes.
传统的电位型 NO 选择性电极由于电位与离子活度对数之间的关系，受到 Nernst 斜率（25°C 时为 59.1 mV/dec）的根本限制。在此，提出了一种基于有序介孔碳（OMC）的固态接触离子选择性电极（ISE）的库仑信号读出，而不是电位响应，用于检测 NO。获得库仑信号的机制基于 OMC 的双电层电容，该电容在恒电位控制下补偿了测量过程中在离子选择性膜/溶液界面处的电位变化。在优化条件下，基于 OMC 的固态接触 NO-ISE 的库仑信号在 1.0×10-8.0×10-6 M 和 8.0×10-8.0×10-6 M 的活度范围内呈现出两个线性响应，检测限为 4.0×10-6 M（3σ/s）。在存在 O 和 CO 以及光照开/关的情况下，所提出的库仑响应也表现出出色的重现性和稳定性。此外，与传统的电位响应和离子色谱法相比，库仑响应在矿泉水中亚硝酸根的检测中具有可接受和可靠的结果。这项工作为使用固态接触离子选择性电极检测离子提供了一种有前途的替代信号读出方法。
