A new strategy for simultaneous determination of 4-aminophenol, uric acid and nitrite based on a graphene/hydroxyapatite composite modified glassy carbon electrode

A novel electrochemical sensor has been fabricated based on a graphene/hydroxyapatite nanocomposite modified glassy carbon electrode (GCE) for the selective and simultaneous detection of 4-aminophenol (4-AP), uric acid (UA) and nitrite ions (NO 2− ) in a phosphate buffer solution (PBS, pH 7.0) for the first time. The modified electrode exhibited improved electrocatalytic activity towards the oxidation of 4-AP, UA and NO 2− in the form of three strong peaks in both the cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. Under optimum conditions, the ternary system comprising 4-AP, UA and NO 2− exhibited linear calibration plots over a wide range of 0.1–425 μM, 1–1000 μM and 3–950 μM with detection limits of 0.29 μM, 0.03 μM and 0.025 μM for 4-AP, UA and NO 2− respectively. The developed sensor displayed high sensitivity and low detection limits coupled with good stability and reproducibility which were attributed to the synergistic effect of graphene and HAP in the nanocomposite. In addition, the fabricated sensor was applied to the determination of UA, 4-AP and NO 2− in urine and tap water samples with satisfactory results.