An Active Transport Mimetic System Based on Thioctic Acid as
Carrier for Alkaline Earth Metal Ions
R. Zuglea,* J. Kambo-Dorsaa and V.P.Y.
aDepartment of chemistry, University of Cape
Coast, Cape Coast, Ghana
bCentral University College, Accra, Ghana
(Received 5 July 2006, Accepted 11 October 2006)
Liquid membranes incorporating thioctic acid
as a carrier to mimic an active transport system for alkaline earth metals has
been described. A transport cell, operating on the same principle as the
Schulman Bridge was used. It has been demonstrated that such a system is capable
of transporting alkaline earth metals against a proton gradient, as driving
force. The potential of thioctic acid to complex and transport these metal ions
particularly Mg2+, Ca2+, and Ba2+ was verified.
Furthermore, this transport phenomenon was extended to some different barium
salts (Cl-, Br-, NO3-, and SCN-)
to determine the effect of nature of anion on the transport of the Ba2+
ions. The order of the transport rate was found to be Ba2+ > Ca2+
> Mg2+ which is inconsistent with the stability of coordination to
the carboxyl group. The rate of transport of Ba2+ ions were found to
decrease with the anion type in the order SCN- > Br- > NO3-
> Cl- which is related to the extent of hydration of the anions.
Keywords: Active transport, Liquid membrane, Alkaline
earth, Thioctic acid, Anion type