Coupling liquid membrane and flow-injection technique as an analytical strategy for copper analysis in saline water

A tandem system based on the coupling of a bulk liquid membrane and a flow injection analysis for the separation, preconcentration and spectrophotometric determination of copper in saline water is presented. The ligand pyridine-2-acetaldehyde benzoylhydrazone has been used as a carrier in the liquid membrane as well as a spectrophotometric reagent for UV-VIS detection. Simultaneous and sequential experimental designs were used to optimise the chosen variables of each technique, respectively. The metal was separated and preconcentrated from the sample with an efficiency of 100.5 ± 0.9% and a metal preconcentration factor of 16.1. The on-line FIA determination was accomplished after metal complexation by the reagent at pH 3. A linear response was obtained in a range from 6.9 to 984.5 µg L^-1 Cu(II), providing a detection limit of 1.8 µg L^-1. Saline matrix and other metal ions were not cause of interferences with relative errors below 4.6% for 50 µg L^-1 of Cu(II) determination. The proposed tandem system was successfully tested using a TMDA-62 certified reference material providing a relative error of + 1.9%; it was also applied to the Cu(II) determination in coastal seawater samples with low relative errors ranging from - 3.8% to 0.0% (using DPASV as reference method).