Vv. Egorov et Yv. Sin'Kevich, pH-ISEs with an expanded measuring range based on calix[4]arenes: specificfeatures of the behaviour and description of the electrode response, TALANTA, 48(1), 1999, pp. 23-38
This article contains a description of pH-ISEs with plasticised PVC membran
es that contain calix[4]arene or p-tertbutylcalix[4]arene as an ionophore a
nd tetradecylammonum nitrate taken in a subequivalent amount relative to ca
lyxarene as an ionic additive. It has been discovered that real ISEs have a
n extraordinarily wide measuring range which is about 1.5-2 pH units wider
then the measuring range of tridecylamine-based ISEs under the same conditi
ons. Just as in the case of amine-type neutral carriers-based pH-ISEs, the
upper detection limit depends on the concentration and lipophilicity of ani
ons and the lower limit, on the concentration and lipophilicity of cations
present in the sample solution. A simple quantitative description of the el
ectrode response and the detection limits of such ISEs is suggested which i
s based on inclusion of extraction equilibria at the membrane/solution inte
rface for two limiting cases: complete dissociation and strong association
of ions in the membrane. Interface equilibria constants that occur in the a
cid and alkali media are estimated experimentally in model extraction syste
ms. Characteristics of the ISEs calculated with use of the estimated consta
nts agree satisfactorily with those measured experimentally. Probable reaso
ns of the expansion of the measuring range of the ISEs considered in compar
ison with ISEs based on amine-type neutral carriers are discussed. (C) 1999
Elsevier Science B.V. All rights reserved.