His-Ser-Gln-Lys-Val-Phe as a selective ligand for the voltammetric determination of Cd2+

An electrochemical sensor for cadmium ions is described which is made by modifying a gold electrode with 3-mercaptopropionic acid followed by covalently coupling the cadmium-selective hexapeptide His-Ser-Gln-Lys-Val-Phe. The resultant electrode had significantly superior analytical performance compared with a glutathione (GSH) modified electrode for the detection of Cd2+, having a greater sensitivity, broader detectable concentration range and a five times lower detection limit of 0.9 nM. Interference from Pb2+ was observed which is an improvement from the GSH modified electrode which had Pb2+ and Cu2+ as interfering ions. The effects of Cu2+, Ni2+, Zn2+, Cr3+ and Ba2+were insignificant.