A study of the kinetics of Cu2+ extraction by 7-(4-ethyl-1-methyloctyl)8-hydroxyquinoline (Kelex 100) has been undertaken in a static transfer cell, where the total concentration of the Cu2+ - Kelex 100 complex In the organic phase is monitored in situ as the reaction proceeds using attenuated total internal reflectance spectroscopy. The temporal characteristics of the extraction of Cu2+ from water into heptane could be accounted for using a simple one-dimensional diffusion model coupled with a reaction-limited interaction between Cu2+ and Kelex 200. Rate constants for the reaction of Kelex 100 and Cu2+ at a model interface were obtained from stopped flow experiments using a neutral micelle (C(12)E(8)) system. These rate constants were used to model the reaction between Cu2+ and Kelex 100 at the heptane-water interface.