Detector Control
Correcting a Waveform for pH Dependence

At a mobile phase pH of 7, the reference potential of the entire pH-Ag/AgCl electrode is the same as that of the Ag/AgCl half-cell. As the mobile phase pH is increased, the pH half-cell potential decreases approximately 0.059 V per pH unit. For example, at a mobile phase pH of 12, the reference potential of the pH half-cell would be -0.295 V relative to the Ag/AgCl half-cell. Therefore, at pH 12, the potentials applied to the working electrode must be raised approximately 0.3 V when switching from the AgCl mode to the pH mode.

For example, two default waveforms for amino acids are provided with Chromeleon: one for use with the AgCl reference electrode mode and one for the pH mode. The waveforms are identical except that, in the pH mode waveform, the potentials are raised by 0.33 V to compensate for an eluent with a pH of 12.7.

Also refer to:

 Defining a Waveform

 Selecting a Default Waveform for Integrated Amperometry