Title: zone pH
Long Title: IUPAC Gold Book - zone pH
DOI: 10.1351/goldbook.11548
Status: current

Definition
pH of the solute zone in pH-zone-refining counter-current chromatography. \[{\rm{pH}}_{\rm{zone}} = \pu{p}K_{\rm{a}} + \log[(K_{\rm{DS}}/K_{\rm{S}}) - 1]\], where \(K_{\rm{DS}}\) is the partition ratio of solute $\ce{S}$ (an indicator for solute hydrophobicity) and \(K_{\rm{S}}\), the dissociation constant of the solute.

Note
According to theoretical analysis two solutes that differ their zone \(\pu{pH}\) values by \(\pu{0.2}\) or greater can be resolved in \(\pu{pH}\)-zone-refining CCC.

Related Term
- pH-zone-refining counter-current chromatography: https://goldbook.iupac.org//terms/view/09947

Source
- PAC, 2017, 90, 181. 'Terminology of separation methods (IUPAC Recommendations 2017)' on page 205 (https://doi.org/10.1515/pac-2017-0111)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/11548/html
- json: https://goldbook.iupac.org/terms/view/11548/json
- xml: https://goldbook.iupac.org/terms/view/11548/xml

Citation: Citation: 'zone pH' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.11548
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Accessed: 2026-04-21T11:10:54+00:00