3,7‐Dioxaazelaamides as Ionophores for Lithium Ion Selective Liquid Membrane Electrodes

Abstract

Lipophilic neutral carriers were synthesized which show Li+/Na+ selectivities of up to ca. 80 in highly lipophilic liquid membranes. The sensor membranes exhibit improved response times and increased lifetimes as compared to systems described earlier. They allow reliable measurements of Li+ in blood serum within the clinical concentration range. A 1 :I Li+/ionophore complex of one representative (N,N,N,N'-tetracyclohexyl-5,5-dimethyl-3,7-dioxaazelaamide) has been prepared, and its structure was elucidated by X-ray analysis.Introduction. -Among the different neutral carrier-based membranes recommended for Li+-selective electrodes [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], only few show acceptable Li+/Na+ selectivities for the potentiometric assay of Li' in blood serum during therapy of manic depressive psychosis

Performance of a highly lipophilic Li+ lonophore in solvent polymeric membranes

“…Under identical experimental conditions it indeed induces a slightly higher Li § over Na + selectivity in membranes than the isologue 2. Potentiometrically determined selectivity factors, log -~ei M,' P~ for solvent polymeric membranes 1 9 (see Table 1) with the ionophores 1 and 2 As reported earlier [4], cyclohexyl instead of alkyl substituents of the amide nitrogen atoms surprisingly favour the Li + over Na + selectivity. 2).…”

“…In solvent polymeric membranes both ETH 227 [28] and the isologue ETH 2137 [4] exhibit remarkable selectivity for Li + over Na § [29]. In solvent polymeric membranes both ETH 227 [28] and the isologue ETH 2137 [4] exhibit remarkable selectivity for Li + over Na § [29].…”

“…Their lipophilicity (water/1-noctanol partition coefficient) is up to 1013'8 so that they can be used in ionselective electrodes with a lifetime of up to 40 000 h even in permanent contact with whole blood or undiluted blood serum.Key words: ionophore for Li +, ion selective electrodes, high lipophilicity, solvent polymeric membranes.In view of the measurement of the lithium ion activity in whole blood, blood plasma or blood serum of patients suffering from manic depressive psychosis there are ongoing efforts to find ionophores which induce a high Li+/Na § selectivity in membranes [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Their lipophilicity (water/1-noctanol partition coefficient) is up to 1013'8 so that they can be used in ionselective electrodes with a lifetime of up to 40 000 h even in permanent contact with whole blood or undiluted blood serum.…”

“…In view of the measurement of the lithium ion activity in whole blood, blood plasma or blood serum of patients suffering from manic depressive psychosis there are ongoing efforts to find ionophores which induce a high Li+/Na § selectivity in membranes [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Assuming a therapeutic range between 0.7 and 1.5 mM Li § and an interference of less than 1% by Na + (worst case, 150 mM Na § a selectivity log rTPot -e /X.LiNa Ol at least --4.3 is required [20].…”

Optical Ion Sensor Based on Second-Harmonic Generation at the Surface of an Ionophore-Incorporated Polyvinyl chloride) Liquid Membrane

“…The lower sensitivity for Li+ of the sensor based on ionophore 4 might be due to the small polarizability of the Li+ complex. 21 The detection limit for Li+ of the sensor based on ionophore 3 was 1 X 10-3 M, the response slope being larger above 1.0X10-1 M Li+ than below that value. The reason for this change in the slope is not clear, but might be due to differences in the average molecular orientation of the Lit-complex at the membrane surface.…”