Comparison of dibenzo-16-crown-5 compounds with pendent amide groups as sodium ionophores in ion-selective electrodes and in solvent extraction
✍ Scribed by Akira Ohki; Kaoru Iwaki; Kensuke Naka; Shigeru Maeda; James J. Collier; Youngchan Jang; Hong-Sik Hwang; Richard A. Bartsch
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 497 KB
- Volume
- 8
- Category
- Article
- ISSN
- 1040-0397
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✦ Synopsis
Potentiometric selectivities for alkali metal, alkaline earth metal and ammonium ions for a series of N,N-dialkyl .qwz-( R)dibenro-16-crown-5-oxyacetamides in solvent polymeric membrane electrodes are determined. For N,N-dipentyl sym-(R)dibenzo-16-crown-5-oxyacetdmides, the Na+/K ' selectivity increases with variation of the R group in the order: hydrogen << propyl (linear alkyl) < isopropyl, neopentyl (branched alkyl). Solvent extractions of sodium and potassium picrates from aqueous solutions into 1,2-dichloroethane were also performed. Ratios of the extraction constants for Na+ and K t ( l o g K p / K z ) are similar in magnitude and show the same trends lor structural variation within the ionophore as do the potentiometric selectivities between Nai and K + (log K E K ) in the polymeric membrane electrodes. From the picrate extraction results. it is deduced that the enhancement in potentiometric selectivity for Na+ over K ' when the R group is changed from hydrogen to propyl arises from increased binding of Na+ and diminished complexation of K + . On the other hand, the enhanced potentiometric selectivity for Nat over K+ when a linear alkyl R group is replaced by a branched alkyl group appears to result from decreased complexation of K i only.