BENZO-18-CROWN-6 AND ITS LARIAT ETHER DERIVATIVES AS IONOPHORES FOR POTASSIUM, STRONTIUM, AND LEAD ION-SELECTIVE ELECTRODES

Ion-selective microelectrodes were prepared by coating a matrix containing the crown ether benzo-18-crown-6 or one of five polyether ring-substituted benzo-18-crown-6 derivatives on a preconditioned silver wire in a flow cell. Responses of the electrodes toward lithium, sodium, potassium, magnesium, calcium, strontium, and lead were measured. Selectivity coefficients were obtained by the matched potential, fixed interference, and separate solution methods. Compared with benzo-18-crown-6, the nature of the side arm in the lariat ether derivatives was found to influence the selectivities in different ways. For specific ionophores, high selectivities of potassium over lithium, sodium, magnesium, calcium, and strontium, of strontium over magnesium and calcium, and of lead over magnesium, calcium, and strontium were demonstrated.