Potentiometric probes used in direct potentiometry are attractive sensing tools. They give information on ion activities, which is often uniquely useful. If, instead, concentrations are desired as sensor output, the ionic strength of the sample must be precisely known, which is often not possible. Here, for the first time, direct potentiometry can be made to report concentrations, rather than activities. It is demonstrated for the detection of monovalent anionic species by using a self-referencing Ag/AgI pulstrode as the reference element instead of a traditional reference electrode. This reference pulstrode releases a discrete quantity of iodide ions from the electrode and the resulting reference potential varies with the activity coefficient of iodide. The effects of activity coefficient on the indicator and reference electrode are therefore compensated and the observed cell potential may now be described in a Nernstian manner against anion concentration, rather than activity. Theoretical simulations and experimental results support the validity of this approach. For most monovalent anions of practical relevance, the potential difference between this approach and from a traditional activity coefficient calculation is less than 0.5 mV. The concept is validated with an all-solid-state nitrate sensor as well as a commercial fluoride-selective electrode, giving Nernstian responses in different ionic strength backgrounds against concentration without the need for correcting activity coefficients or liquid junction potentials.

中文翻译：

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阴离子浓度的直接电位计感测（非活性）。

直接电位计中使用的电位计探头是有吸引力的传感工具。它们提供有关离子活性的信息，这通常是唯一有用的。相反，如果需要浓度作为传感器输出，则必须精确知道样品的离子强度，这通常是不可能的。在这里，第一次可以通过直接电位计报告浓度而不是活性。通过使用自参考Ag / AgI脉冲电极作为参考元素代替传统参考电极，证明了该方法可检测单价阴离子。该参考脉冲电极从电极释放出离散量的碘离子，并且所得参考电位随碘化物的活度系数而变化。因此，可以补偿活度系数对指示剂和参比电极的影响，现在可以以能斯特对阴离子浓度而不是活度的方式描述观察到的细胞电势。理论仿真和实验结果证明了该方法的有效性。对于大多数具有实际相关性的单价阴离子，此方法与传统活性系数计算方法之间的电势差小于0.5 mV。该概念已通过全固态硝酸盐传感器以及市售的氟化物选择性电极进行了验证，无需校正活性系数或液体结电势，即可在不同的离子强度背景下针对浓度进行能斯登响应。