A new simple and reliable method for rapid and selective extraction and determination of trace levels of Ag+ ion is developed. Silver ions are adsorbed quantitatively during passage of aqueous samples through octadecyl silica membrane disks modified with some recently synthesized mixed aza-thioether crowns containing 1,10-phenanthroline sub-unit. Almost all matrix elements were found to pass through the disk to drain. The retained Ag+ ions are then stripped from the disk with a minimal amount of thiosulfate solution as eluent and subsequently measured by atomic absorption spectrometry. The proposed method permitted large enrichment factors of about 200 and higher. The limit of detection of the proposed method is 100 ng Ag+ per 1000 ml. The method was applied to the recovery of Ag+ ions from different synthetic and water samples. (C) 2002 Elsevier Science B.V. All rights reserved.