Designing potentiometric sensor materials for the determination of organic ionizable substances in HPLC

Abstract

This article provides a model to explain the response of liquid membrane type potentiometric electrodes towards organic ions in HPLC systems. The model is a synthesis of data from 7 recent articles from our group on the determination of several classes of compounds (organic acids, amines, beta-blockers, clenbuterol, mucolytic drugs and aminoalcohols) with potentiometric detection in HPLC. The presented model uses the difference in chemical potential of the analyte ion in the eluent and in the membrane phase as the sensitivity determining factor. Methods used to estimate this difference in chemical potential are compared. For liquid membrane coatings containing no selectively interacting (complex forming) ionophores, this difference could be estimated from calculated log P (lipophilicity) and P (polarizability) values for the analyte ions. If complex forming agents are present, the extra interaction of the analyte ion with the complex forming agent can be estimated via a solvation parameter model. In the latter case, molecular modeling may also be useful.