The enantioselective partitioning behaviour of (D/L)-phenylalanine into an organic phase containing an alkylated amino acid in the presence and absence of copper (II) ions has been systematically investigated. In this paper equilibrium constants are presented for the extraction of copper by organic phase N-decyl-(L)-hydroxyproline and (D/L)-phenylalanine by copper (II) N-decyl-(L)-hydroxyproline as well as the partition of both species into a mixed hexanol/decane solvent in the absence of any organic-phase complexing agents. The enantioselective equilibrium partitioning constants were found to be 0.149 +/- 0.002 for the L-isomer and 0.228 +/- 0.002 for the D-isomer. A model has been developed to describe the simultaneous extraction of (D/L)-phenylalanine by organic-phase copper (II) N-decyl-(L)-hydroxyproline. Kinetic extraction studies in a Lewis-type constant area/volume cell indicate a first-order forward rate constant for the L-isomer of 5.2 +/- 1.3 x 10(-4) m(sM)(-1) and for the D-isomer 8.5 +/- 1.6 x 10(-4) m(sM)(-1).