The transport of alkali metal ions was studied in liquid membrane systems based on 2,3-benzo-11-methyl-18-crown-6 (I), 2,3-benzo-8,15-dimethyl-18-crown-6 (II), and 2,3-benzo-8,11,15-trimethyl-18-crown-6 (III). Metal ion migration involves a pair of consecutive 1st order processes when the metal ion concentration in the aqueous phase and the crown carrier concentration in the membrane phase are comparable. The rate constants for Na+, K+, and Rb+ complexes are k1 = 0.142, 0.180, 0.162 h-1 (I), 0.136, 0.165, 0.145 h-1 (II), and 0.130, 0.141, 0.123 h-1 (III) and k2 = 0.213, 0.198, 0.211 h-1 (I), 0.211, 0.201, 0.205 h-1 (II), and 0.195, 0.193, 0.197 h-1 (III), resp. The effects of carrier structure and coordination capacity on cation transport are discussed.

Key words: CROWN ETHER COMPOUNDS, TRANSMISSION, ALKALI METAL ION, KINETIC STUDY