▎ 摘　　要

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 (NO2- ) 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 NO2- 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 NO2- exhibited linear calibration plots over a wide range of 0.1-425 mu M, 1-1000 mu M and 3-950 mu M with detection limits of 0.29 mu M, 0.03 mu M and 0.025 mu M for 4-AP, UA and NO2- 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 NO2- in urine and tap water samples with satisfactory results.