Simultaneous determination of the complexing capacity and conditional stability constant of soluble copper(II) complexes in natural-water samples by using a chelate extraction technique

Based on a back-extraction of bis(4,4,4-trifluoro-1-(2-thienyl)-1,3-butaned ionato)copper(II), a method for the simultaneous determination of the coppe r(II) complexing capacity of natural water and the conditional stability co nstant of copper(II) complex with naturally occurring ligands was developed . The feasibility of the proposed method was confirmed using nitrilotriacet ic acid and ethylenediamine-N,N'-dipropionic acid instead of naturally occu rring ligands. It was then applied to a pond-water sample. The results indi cated that two types of copper(II) complexes having different stabilities w ere formed upon the addition of copper(II) to the sample. By using the copp er(II) complexing capacity and the conditional stability constant, the dist ribution of copper(II) species in pond water was calculated. It was found t hat most of the copper(II) in pond water exists as a complex with a natural ly occurring ligand, and that the concentration of free copper(II) ion is e xtremely law.