Several ligands were designed as plausible reagents for the spectrophotometric analysis of uranyl in aqueous solutions. The ligand L 2À 3 = 3,3′-(ethane-1,2-diylbis(methylazanediyl))bis(methylene)bis(4-hydroxybenzenesulfonate) was found to fit best the requirements. The results point out that carboxylate substituents compete with the phenolate substituents as binding sites to the central uranium cation and therefore decrease the usefulness of ligands containing both carboxylate and phenolate substituents as analytical spectrophotometric reagents.