School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641, China.
State Key Laboratory of Biobased Material and Green Papermaking, School of Food Science and Engineering, Qilu University of Technology, Shandong Academy of Sciences, Jinan 250353, China.
Anal Chem. 2021 Feb 23;93(7):3353-3361. doi: 10.1021/acs.analchem.0c02266. Epub 2021 Feb 8.
A novel approach has been developed for the selective determination of cations or anions based on the application of Fourier transformed staircase sinusoidal voltammetry (FT-SC-SV) in combination with the interface between two immiscible electrolyte solutions (ITIES) in the four-electrode configuration. The electrochemistry at the ITIES provides a very simple yet sensitive platform for the detection of a broad spectrum of redox inactive ions and even the neutral (bio)molecules that can be charged (e.g., protonated in appropriate pH). FT-SC-SV employs a complex potential excitation, i.e., a large-amplitude sine wave superimposed onto a dc bias potential that is stepped/scanned throughout the potential window. The response current is subsequently analyzed in the frequency domain by FT. Although the ions have close standard/formal transfer potential, discrimination and selective detection can be achieved by the higher harmonics. Feasibility and reliability of the proposed approach were verified with two pairs of ions that have very close transfer potentials across the ITIES and were chosen as the model systems. Besides, the additivity of the ionic current magnitude on concentration measured either in the mixture of ionic analytes or in individually prepared solutions containing the separate ionic analyte was tested. The experimental results prove that the principle of additivity holds. Compared with the traditional voltammetry, FT-SC-SV is simpler and more efficient in discrimination and quantification of apparently indistinguishable ion transfer from the viewpoint of thermodynamics. This demonstration may provide a new way for analytical detection of a broad range of redox inactive ions in terms of both fundamentals and applications.
一种新方法已经被开发出来，用于基于傅里叶变换阶梯正弦波伏安法（FT-SC-SV）与四电极配置中的两相不混溶液体界面（ITIES）的应用，来选择性地测定阳离子或阴离子。ITIES 处的电化学提供了一个非常简单但灵敏的平台，用于检测广泛的氧化还原非活性离子，甚至可以检测可以被荷电的中性（生物）分子（例如，在适当的 pH 值下质子化）。FT-SC-SV 采用复杂的电势激励，即大振幅正弦波叠加在直流偏置电势上，该偏置电势在整个电势窗口中逐步/扫描。随后通过 FT 对响应电流进行频域分析。尽管离子具有相近的标准/形式转移电势，但可以通过高次谐波实现区分和选择性检测。通过两对穿过 ITIES 具有非常接近转移电势的离子进行验证，选择它们作为模型系统，验证了所提出方法的可行性和可靠性。此外，还测试了在离子分析物混合物中或分别在含有单独离子分析物的单独溶液中测量的浓度上的离子电流大小的加和性。实验结果证明了加和性原则的有效性。与传统伏安法相比，从热力学角度来看，FT-SC-SV 在区分和定量明显无法区分的离子转移方面更简单、更高效。这一演示可能为从基本原理和应用的角度广泛检测氧化还原非活性离子提供了一种新方法。
