Pankratova Nadezda, Ghahraman Afshar Majid, Yuan Dajing, Crespo Gastón A, Bakker Eric
Department of Inorganic and Analytical Chemistry, University of Geneva , Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland.
ACS Sens. 2016 Jan 22;1(1):48-54. doi: 10.1021/acssensors.5b00015. Epub 2015 Oct 22.
The work dramatically improves the lower detection limit of anion selective membranes at environmental pH by using local acidification to suppress hydroxide interference at the membrane surface. Three separate localized acidification strategies are explored to achieve this, with ionophore-based membrane electrodes selective for nitrite and dihydrogen phosphate as guiding examples. In a first approach, a concentrated acetic acid solution (ca. 1 M) is placed in the inner filling solution of the PVC-based membrane electrode, forcing a significant acid gradient across the membrane. A second strategy achieves the same type of passive acidification by using an external proton source (fast diffusive doped polypropylene membrane) placed in front of a potentiometric solid contact anion selective electrode where the thin layer gap allows one to observe spontaneous acidification at the opposing detection electrode. The third approach shares the same configuration, but protons are here released by electrochemical control from the selective proton source into the thin layer sample. All three protocols improve the limit of detection by more than 2 orders of magnitude at environmental pH. Nitrite and dihydrogen phosphate determinations in artificial and natural samples are demonstrated.
这项工作通过利用局部酸化来抑制膜表面的氢氧根干扰，极大地提高了环境pH下阴离子选择性膜的检测下限。为实现这一目标，探索了三种不同的局部酸化策略，并以对亚硝酸盐和磷酸二氢根具有选择性的基于离子载体的膜电极作为指导示例。在第一种方法中，将浓醋酸溶液（约1 M）置于基于PVC的膜电极的内部填充溶液中，迫使膜上形成显著的酸梯度。第二种策略通过在电位型固体接触阴离子选择性电极前放置外部质子源（快速扩散掺杂聚丙烯膜）来实现相同类型的被动酸化，其中薄层间隙使人们能够在相对的检测电极处观察到自发酸化。第三种方法具有相同的配置，但质子在这里通过电化学控制从选择性质子源释放到薄层样品中。所有这三种方案在环境pH下都将检测限提高了两个以上数量级。展示了在人工和天然样品中对亚硝酸盐和磷酸二氢根的测定。
