Flow-Injection Potentiometric Detection of Metal Ions Based on Tungsten Oxide Electrode

The use of a tungsten oxide electrode for potentiometric flow-injection analysis of transition metal ions is described. The effect of a variety of experimental conditions, including the carrier pH, the types of ligands and their concentrations, was studied. It was found that the best sensitivity for the ions tested was obtained using EDTA as a ligand. The electrode exhibited a linear response for Fe3+, Cu2+, Pb2+ and Ca2+ in the range of 2.5 × 10-4 M to 2 × 10-3 M using with 1 × 10-3 M EDTA at pH 5.0 as carrier. The detection limits were found to be between 1 × 10-5 to 5 × 10-5 M. Reproducibility for Fe3+ was about 1.7% with a stable baseline potential.