Abstract
A series of crown ethers (12- to 21-membered) and various alkanoic acids with long hydrocarbon chains were examined as carriers for the active and competitive transport of alkaline earth metal cations (Mg2+, Ca2+, and Ba2+) in a chloroform liquid membrane system.
The transport of all cations except Mg2+ was efficiently carried out, on the condition that a mixture of crown ether and alkanoic acid was used. This confirms the cooperative action of these two compounds as carriers. Transport efficiency was found to depend greatly on the structure of alkanoic acid and to a slight extent on the ring size of crown ether. Of the alkanoic acids examined, 2-bromododecanoic acid was the most efficient co-carrier. Unsubstituted alkanoic acids (C8C18) combined with dicyclohexano-18-crown-6 or 21-crown-7 were found to transport Ba2+ exclusively in the competitive system.
