Electrochemical oxidative determination of 4-nitrophenol based on a glassy carbon electrode modified with a hydroxyapatite nanopowder

A glassy carbon electrode was modified with hydroxyapatite nanopowder (HA-NP) and characterized in terms of electrochemical oxidation of 4-nitrophenol (4-NP) via cyclic voltammetry, differential pulse voltammetry, chronoamperometry, and chronocoulumetry. The oxidation peak current of 4-NP at the modified electrode was increased (compared to the bare GCE), thus indicating that the HA-NP exhibits a remarkable enhancement effect on the electrochemical oxidation of 4-NP. The effects of loading with HA-NP, pH value, scan rate and accumulation time were examined. The oxidation peak current of 4-NP is proportional to its concentration in the range from 1.0 mu M to 300 mu M, with a correlation coefficient of 0.9996. The detection limit is 0.6 mu M (at an S/N = 3). The method is simple, selective and sensitive. It was successfully applied to the determination of 4-NP in water samples, with recoveries ranging from 96% to 104%.