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potentiometric selectivity coefficient

A coefficient which defines the ability of an ion-selective electrode to distinguish a particular ion from others. The selectivity coefficient, K A,B pot, is evaluated by means of the emf response of the ion-selective electrode in mixed solutions of the primary ion, A, and interfering ion, B (fixed interference method) or less desirable, in separate solutions of A and B (separate solution method). The activities of the primary ion, A, and the interfering ion, B, at which K A,B pot is determined should always be specified, as the value of K A,B pot is defined by the modified Nikolsky–Eisenman equation. The smaller the value of K A,B pot the greater the electrode's preference for the principal ion, A. Comment: The terms selectivity constant and selectivity factor are frequently used instead of selectivity coefficient. However, in order to standardize the terminology associated with ion-selective electrodes, use of the term selectivity coefficient is recommended, as is the fixed interference method for its evaluation.This selectivity coefficient is not identical to the similar term used in separation science.
Source:
PAC, 1994, 66, 2527 (Recommendations for nomenclature of ionselective electrodes (IUPAC Recommendations 1994)) on page 2532
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Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook.
Last update: 2014-02-24; version: 2.3.3.
DOI of this term: doi:10.1351/goldbook.P04791.
Original PDF version: http://www.iupac.org/goldbook/P04791.pdf. The PDF version is out of date and is provided for reference purposes only. For some entries, the PDF version may be unavailable.
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