Department of Chemistry, Oregon State University, Corvallis 97330, Oregon, United States.
Anal Chem. 2022 Jun 14;94(23):8302-8308. doi: 10.1021/acs.analchem.2c00748. Epub 2022 Jun 3.
Solid-contact ion-selective electrodes (ISEs) have the inherent advantage of being miniaturized in addition to maintaining high selectivity and sensitivity of the ionophore-based ISE. The major disadvantage of ISEs is the necessity of performing a calibration curve (varying the intercept in the linear calibration curve equation) each time before running experiments, which limits their application as one-time disposable sensors or for use in remote water sample analysis. To overcome these challenges, we designed a unique back contact made of 3,4-ethylenedioxythiophene (EDOT) and 4-(2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl-methoxy)-1-butanesulfonic acid, sodium salt (EDOT-S). The calibration-free ISEs showed near Nernstian responses of 57.2 ± 0.2 mV/log [K] and 28.5 ± 0.3 mV/log [Ca], while maintaining their respective selectivity against major interfering ions. The detection limits for Ca and K ISEs were 0.45 ± 0.01 and 1.68 ± 0.18 μM, respectively. The charging cycles of the PEDOT: PEDOT-S back contact allowed us to fix the background potential at a desired fixed intercept value across different ionophores (K, Ca). This protocol was used to determine the K and Ca contents in creek water samples. The activity and concentration of [Ca] and [K] in a local creek was found to be 257 ± 7.3 and 28.1 ± 1.1 μM, respectively.
固体接触离子选择性电极（ISE）除了保持基于离子载体的 ISE 的高选择性和灵敏度外，还有小型化的固有优势。ISE 的主要缺点是每次运行实验前都需要进行校准曲线（改变线性校准曲线方程中的截距），这限制了它们作为一次性传感器或用于远程水样分析的应用。为了克服这些挑战，我们设计了一种独特的背面接触，由 3,4-亚乙基二氧噻吩（EDOT）和 4-（2,3-二氢噻吩[3,4-b][1,4]二恶英-2-基-甲氧基）-1-丁烷磺酸，钠盐（EDOT-S）制成。无校准 ISE 表现出近 Nernstian 响应，对于 K 的响应为 57.2 ± 0.2 mV/log [K]，对于 Ca 的响应为 28.5 ± 0.3 mV/log [Ca]，同时保持对主要干扰离子的各自选择性。Ca 和 K ISE 的检测限分别为 0.45 ± 0.01 和 1.68 ± 0.18 μM。PEDOT：PEDOT-S 背面接触的充电循环使我们能够将背景电势固定在不同离子载体（K、Ca）的期望固定截距值。该方案用于确定溪流水样中的 K 和 Ca 含量。当地小溪中的[Ca]和[K]的活度和浓度分别为 257 ± 7.3 和 28.1 ± 1.1 μM。
