Nine monoazathiacrown ethers have been synthesized and explored as ionophores for polymeric membrane Ag(+)-selective electrodes. Potentiometric responses reveal that the ion-selective electrodes (ISEs) based on 2,2'-thiodiethanethiol derivatives can exhibit excellent selectivities toward Ag(+). The plasticized poly(vinyl chloride) membrane electrode using 22-membered N(2)S(5)-ligand as ionophore has been characterized and its logarithmic selectivity coefficients for Ag(+) over most of the interfering cations have been determined as <-8.0. Under optimal conditions, a lower detection limit of 2.2x10(-10)M can be obtained for the membrane Ag(+)-ISE.