To expand the knowledge of the extraction for metal ions with an amino acid derivative, a new extraction agent having proline as a functional moiety, 1-{2-[di-(2-ethylhexyl)carbamoyl)ethyl}pyrrolidine-2-carboxylic acid (D2EHCEP), has been synthesized in this study. In addition, a polymer inclusion membrane (PIM) has been prepared using D2EHCEP as a carrier and cellulose triacetate (CTA) as a polymer matrix to examine the solid-liquid extraction and membrane transport of metal ions. The PIM containing D2EHCEP exhibited an active transport of copper(II) against the concentration gradient and no transport of indium(III). This observation may be due to the difference in the structures of their extracted complexes, that is, indium(III) is only complexed with carboxyl groups through electrostatic interaction, whereas copper(II) forms chelate-complexes with amino and carboxyl groups of D2EHCEP. The influences of the aqueous and membrane components on the permeability of copper(II) were studied to elucidate the transport mechanism of metal ions across the PIM. Their results suggest that the rate-determining step for the permeability rate at high pH is the mass transfer of a metal complex across the membrane phase. The mass transfer coefficients in the aqueous boundary layer (k(f)) and in the membrane phase (k(m)) were determined based on the diffusion model. The mass transfer coefficients obtained were k(f) = 3.7 x 10(-6) m s(-1) and k(m) = 4.3 x 10(-10) m s(-1).