Design and application of potentiometric sensors for the determination of mefenamic and phenylanthranilic acids

Characteristics, performance and applications of potentiometric membrane sensors are described for the determination of mefenamic and phenylanthranilic ions. Ion associates of mefenamic, ClO₄^-, and phenylanthranilic ions with crystal violet (counter-cation) as ion exchange sites have been used as ionophores in the plasticized one- and two-layer membrane ion-selective electrodes. The LOD is reported to be 8.4 × 10^-5 M for mefenamic acid, and 5.1 × 10^-5 M for phenylanthranilic acid. The cations of basic dyes (crystal violet) are characterized by significant delocalization of the positive charge and polarizability. This may explain the better selectivity of the developed sensors. These sensors were used for the direct assay of mefenamic and N-phenylanthranilic acids in model solutions and applications studied in commercial pharmaceutical preparations.