A simple and reliable method for rapid and selective separation and preconcentration of trace amounts of Cu2+ ions front different aqueous samples for the measurement by atomic absorption spectrometry is presented. By the passage of aqueous samples through an octadecyl-bonded silica membrane disk modified by 1-hydroxy-2-(prop-2'-enyl)-4-(prop-2'-enyoxy)-9,10-anthraquinone, the Cu2+ ions adsorb quantitatively and almost all matrix elements will pass through the disk to drain. The retained copper ions are then stripped from the disk by a minimal amount of nitric acid as eluent. The proposed method permitted large enrichment factors of 400 and higher. The limit of detection of the method is 100 ng Cu2+ per 1000 mL. The effects of various cationic interferences on the recovery of copper in binary mixtures were studied. The method was successfully applied to the determination of copper in SRM bovine liver, tea leaves, and a synthetic seawater sample.