The possibility of developing a permeation based method for on-line monitoring of U(VI) ions in aqueous streams has been examined by studying the transport behavior of UO22+ ions across poly(perfluorosulfonic) acid membrane commercially available as a Nafion-117. UO22+ ions present in the feed diffuse across the Nafion-117 membrane to react with the metallochromic reagent Br-PADAP, and form a red-violet colored complex in the receiver compartment. The concentration of U(VI) ions in the receiver compartment could be measured by monitoring the change in absorbance of the U(VI)-Br-PADAP complex at 578 nm. The spectral interference of cations in U(VI) determination was eliminated by using a masking reagent in the receiver compartment. The effects of other experimental parameters such as the presence of different cations and anions in the feed solution (0.01 M HNO3) and feed-to-receiver phase volume ratio were also studied. (C) 2010 Elsevier B.V. All rights reserved.