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Potentiometric Theory

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    The origin of the measured potential at an indicator electrode is most generally the separation of charge across an interface between solutions of differing ionic strengths (an inner solution at fixed analyte activity and an outer solution with variable analyte activity).

    The mechanism leading to this charge separation varies with electrode type. After defining what is meant by a junction potential, we will consider two types of indicator electrodes:

    1. the metallic direct indicator electrode, whose response involves a surface or solution redox reaction, and
    2. the membrane electrode, or ion-selective electrode (ISE).

    Click here to learn about junction potentials.

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