Response Characteristics of Copper‐Selective Polymer Membrane Electrodes Based on a Newly Synthesized Macrocyclic Calix[4]arene Derivative as a Neutral Carrier Ionophore

Abstract

AbstractA novel macrocyclic calix[4]arene derivative was examined as an ionophore for ion‐selective polymeric membrane electrode toward Cu+2 ions. The sensor showed a near Nernstian response for Cu(II) ions over a concentration range from 8.1×10−6 to 1.0×10−2 mol L−1 with a slope of 34.2±0.4 mV per concentration decade in an acidic solution (pH 5). The limit of detection was 0.47 µg mL−1. It had a response time of <20 s and can be used for at least 3 months without any divergence in potentials. The influence of plasticizer as well as the amount of lipophilic anionic site additive in the sensing membrane was discussed. It was shown that membrane electrodes formulated with the ionophore and appropriate anionic additive exhibited enhanced potentiometric response toward Cu2+ over all other cations tested. Since selectivity toward Cu2+ ions is decreased in the presence of high amount of the anionic additive, the ionophore can function as neutral carriers within the organic membrane phase. Validation of the assay method revealed good performance characteristics, including long life span, good selectivity for Cu2+ ions over a wide variety of other metal ions, long term response stability, and high reproducibility. The sensors were used for direct measurement of copper content in different rocks collected from different geological zones. The results agreed fairly well with data obtained using atomic absorption spectrometry.