Determining copper ions in water using electrochemiluminescence

The detection of copper ions in aqueous solution using electrochemiluminescence (ECL) is reported. ECL is generated by reducing Cu^2+ ions to Cu+ with hydroxylamine hydrochloride and then complexing with the chelating agent 2,9-dimethyl-1,10-phenanthroline (dmp) to form Cu(dmp)2+, followed by oxidation in the presence of tri-n-propylamine (TPrA). The ECL intensity peaks a potential corresponding to oxidation of both TPrA and Cu(dmp)2+, indicating that the emission is from a Cu(dmp)2+ metal-to-ligand charge transfer excited state. Conditions for ECL emission were optimized and used to generate a calibration curve that was linear over the 0.1-5mg/l (ppm) range. The theoretical limit of detection was 6µg/l (ppb), with a practical limit of detection of 0.1ppm. The ECL of several metal ions other than copper with dmp, and effects on Cu(dmp)2+ ECL were also examined.