Abstract: Ion-selective compositions which comprise an ion carrier, a compound capable of solvating the ion carrier, and a supporting matrix are disclosed.The ion carriers of this invention are hemispherand compounds represented by the formula ##STR1## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently hydrogen, alkyl, alkenyl, cycloalkyl, aryl or a heterocyclic group; and X is benzyl or an electron donating group capable of forming at least one coordinating site for sodium ions. A preferred hemispherand according to this invention is 2'-benzyloxy-3,3"-[2,6-pyridylenebis(methyleneoxymethylene)]-2,2"-tetramet hylenedioxy-5,5',5"-trimethyl-1,1':3',1"-terphenyl. These compounds and the compositions containing same are particularly useful in ion-selective electrodes. Such an electrode is capable of selectively transporting sodium ions in preference to other cations. Dry-operative electrodes using these ion-selective compositions as membranes are also disclosed.