Behavior and calibration of the copper(II) ion-selective electrode in high chloride media and marine waters

The response of the solid-state Cu(II) ion-selective electrode in high chloride media was investigated and found to be Nernstian under normal laboratory and field measurement conditions. The previously reported "non-Nernstian" behavior has been identified as a combination of electrode fouling, due to specific storage and measurement conditions, and the action of stoichiometric levels of a Lewis base on the standard addition method of electrode calibration. Electrode calibration by external Cu(II) activity buffers in artificial seawater is described. The copper activity of the buffers is calculated from an ion-interaction model, and the electrode response in these buffers is shown to be consistent with that in chloride solutions over 10 orders of magnitude copper concentration and from pH 8 to 2.