ion-exchange isotherm

https://doi.org/10.1351/goldbook.I03169
The concentration of a counter-ion in the ion exchanger expressed as a function of its concentration in the external solution under specified conditions and at constant temperature.
Source:
PAC, 1993, 65, 819. 'Nomenclature for chromatography (IUPAC Recommendations 1993)' on page 854 (https://doi.org/10.1351/pac199365040819)