Application of a chelite P modified carbon paste electrode to copper analysis and speciation

A carbon paste electrode modified with the commercial resin Chelite P, containing amino-phosphonic groups, was used in the determination and speciation of copper. Copper analysis was performed with cyclic voltammetry and differential pulse voltammetry, allowing copper determination in the mu g/L level. A detection limit of 1.9 mu g/L (3 sigma) was found for a 10 min preconcentration. Interferences from other ions and organic substances were examined. For speciation purposes, a ligand competition methodology was used and different model ligands in solution were tested. Copper complexes were characterized as a function of their thermodynamic and kinetics properties. Results were compared with those obtained employing a strong chelating resin (containing iminodiacetic acid) as electrode modifier. The method was applied to a water sample from the Jarama river in Madrid, where copper was mainly present as strong low-dissociating complexes.