The properties of octylsulfanylacetic acid in pertraction of cations, especially lead(II), were investigated. Basic physico-chemical characteristics of the carrier, i.e., the dissociation constant K-a and surface tension sigma of its solution in 1,2-dichloroethane, were determined. A multimembrane hybrid system composed of a liquid membrane and two polymer cation-exchange membranes (Nafion-117) was used as the transport cell. The following order of selectivity was observed: Pb(II)>> Ca(II)approximate to K(I), with the separation factors alpha(Pb)(Ca) and alpha(Pb)(K) in the range of 4-45 and 6-47, respectively. The maximum output fluxes of lead(II) varied from 1.7 to 6.87. 10(-12) Mol cm(2)s(-1) depending on the carrier concentration (0.05-0.1 mol dm(-3)) in a liquid membrane. (C) 2009 Elsevier B.V. All rights reserved.