Simultaneous detection of Pb2+, Cu2+ and Hg2+ by differential pulse voltammetry at an indium tin oxide glass electrode modified by hydroxyapatite.

A novel electrochemical sensor basing on an indium tin oxide (ITO) glass electrode modified by hydroxyapatite (HAp) film was fabricated by electrodeposited method for simultaneous detection of Pb 2+ , Cu 2+ and Hg 2+ using differential pulse voltammetry (DPV). Various experimental parameters such as supporting electrolyte and pH were optimized. Under the optimal conditions, the electrode needs no accumulate time. The electrode showed linear correlation in the ranges of 1 × 10 −7 to 1 × 10 −6  M and 3 × 10 −6 to 1 × 10 −5  M for Pb 2+ , 1 × 10 −7 to 1 × 10 −6  M and 1 × 10 −6 to 1 × 10 −5  M for Cu 2+ , and 1 × 10 −7 to 1 × 10 −5  M for Hg 2+ . The limits of detection (S/N = 3) were 1 × 10 −12 , 1 × 10 −12 , 8 × 10 −8  M for Pd 2+ , Cu 2+ and Hg 2+ , respectively. Meanwhile, the developed electrode showed excellent anti-interference capabilities and selectivity with other heavy metal ions and common ions. The electrode has been successfully applied to the detection of above heavy metal ions in tap water. Above all, two major detection mechanisms of developed electrode were also researched in this work. The mechanism of filling Ca deficiency due to that the radiuses of Pb 2+ and Cu 2+ are similar to Ca 2+ , so Pb 2+ and Cu 2+ can fill in the deficiency. That is why the detection limits of Pb 2+ and Cu 2+ are much lower than Hg 2+ . When Ca deficiency has been almost filled, the detection of Pb 2+ and Cu 2+ based on the mechanism of surface adsorption. Because the radius of Hg 2+ is not similar to Ca 2+ , Hg 2+ cannot fill in the deficiency. The detection of Hg 2+ mainly based on the mechanism of surface adsorption. The OH − on the surface of HAp plays a major role in the adsorption of heavy metal ions. [ABSTRACT FROM AUTHOR]