A Comparison of Neutral Mg²⁺-Selective Ionophores in Solvent Polymeric Membranes: Complex Stoichiometry and Lipophilicity

Abstract

Monopodal and oligopodal Mg²⁺-selective ionophores were characterized by their selectivity coefficients (Separate Solution Method, SSM) in plasticized poly(vinyl chloride) (PVC) membranes. Based on a theoretical model published earlier, the stoichiometry of the Mg²⁺-ligand complexes was estimated while referring to the optimum molar ratio of anionic sites relative to ionophore. The sensitivity of malondiamide substituted azacrown compounds to the varying lipophilicity of the plasticizer, and to the addition of anionic sites was compared with malondiamide derivatives attached to a benzene core. In addition, the lipophilicity of these ligands was determined. In conclusion, the two classes of ionophores were rated concerning their use in human blood and urine specimens.