Inverted poly(vinyl chloride)–liquid membrane ion-selective electrodes for high-speed batch injection potentiometric analysis

Abstract

Sodium and potassium ion-selective electrodes based on the ionophores valinomycin and tetramethyl-p-tert-butylcalix[4]arene tetraacetate immobilized in a poly(vinyl chloride) membrane were fabricated for use in an inverted configuration for batch injection (BI). The results suggest that BI can be used for routine assays involving these and similar electrodes. Peak shapes obtained under fast and zero stirring conditions are contrasted with those obtained using flow injection (FI). It is concluded that, unlike FI, BI peaks are primarily obtained under kinetically limiting conditions with negligible dispersion. This enables changes in over-all potential arising from surface and bulk effects to be clearly distinguished and will therefore provide an important tool for studying fundamental membrane exchange processes. The analytical performance is characterized by a fast, sensitive and reproducible response. Applicability to assays of mineral water is illustrated.