Abstract: Concentrations of large organic cationic species in aqueous solution are measured as a function of potentiometric response, employing a cation-selective electrode having a high degree of selectivity for large organic cationic species with respect to both smaller organic cationic species and inorganic cationic species. The electrode is formed with a cation-selective membrane component composed of a polymeric matrix having dispersed or dissolved therein a cation exchange material whose counter-anion is a high molecular weight alkyl or alkaryl sulfonate or sulphate. By proper choice of the cationic moiety of the cation exchange material, the electrode may be made selective for a variety of large organic cationic species, including a number of such species which are of pharmaceutical or clinical interest, thereby enabling potentiometric assays for such species.

Abstract: The potentiometric responses caused by ion activity changes in solution are measured with an electrode formed by coating an ion exchange material which is molecularly dispersed throughout an insoluble film-forming polymeric matrix directly onto a conductive substrate such that an oxidation-reduction mechanism is not operative in the response of said electrode to the activity of ions in said solution.

Abstract: An organic liquid extractant of at least one oxime, selected from the group consisting of ketoximes and .alpha.-hydroxyoximes dissolved in an organic solvent, useful in separating nickel from cobalt in process solutions or in recovering both nickel and cobalt from process solutions, is treated with a salt of hydroxylamine at intervals to maintain the activity of the oxime in the extractant. The organic extractant can also contain sulfonic acids to facilitate treatment of more acid process solutions and is treated with a hydroxylamine salt to regenerate oxime degraded by the highly acid process solutions, the extractant itself and the concentrated acidic stripping solutions.