Sodium 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.sup.1, R.sup.2, R.sup.3, and R.sup.4 are independently hydrogen, alkyl, alkenyl, cycloalkyl, aryl or a heterocyclic group and R represents Z-decyl, Z-octyl, 3-octyl, and cyclohexyl methyl.