Ion-Selective Electrodes Based on Adamantylcalix[4,8]arenes for the Determination of Alkali Cations

Calix[4,8]arenes bearing adamantyl substituents in the upper rim and ethoxycarbonylmethoxy groups in the lower rim of the macrocycle were proposed as ionophores in membranes of ion-selective electrodes (ISEs) for determining alkali cations. Depending on the number of phenolic fragments (n) in the calixarene molecule, ISEs respond to either sodium (n = 4) or cesium (n = 8) ions. Sensors based on membranes that, along with ionophores, contain tetraphenyl borate ions as a lipophilic additive are selective for Na and Cs ions in the presence of other alkali metals. They exhibit almost theoretical responses over the concentration range from 1 × 10–4 to 1 × 10–1 M at pH 5.5–12 for Na-SE and pH 3–11 for Cs-SE, respectively.