Preparation of a reduced graphene oxide/poly-l-glutathione nanocomposite for electrochemical detection of 4-aminophenol in orange juice samples

A novel electrochemical sensor, for the detection of 4-aminophenol (4-AP), was generated by electrodeposition of poly-l-glutathione (P-l-GSH) onto reduced graphene oxide (RGO) to form a RGO/P-l-GSH composite matrix on a glassy carbon electrode (RGO/P-l-GSH/GCE). The morphology and structure of the RGO/P-l-GSH modified GCE were characterized by scanning electron microscopy (SEM), FT-IR spectroscopy and electrochemical impedance spectroscopy. As an electrochemical sensor, the RGO/P-l-GSH modified GCE composite exhibited strong catalytic activity toward the oxidation of 4-AP which was demonstrated by cyclic voltammetry (CV) and chronoamperometry. Furthermore, the electrochemical sensor exhibited an excellent current response for 4-AP over a wide linear range of 0.4 μM to 200 μM (R² = 0.9934) with a lower detection limit (LOD) of 0.03 μM (S/N = 3), as well as a sensitivity of 27.2 (μA μM^-1 cm^-2) and excellent selectivity, reproducibility and stability. The electrochemical sensor provides good anti-interference ability in the presence of glucose, fructose, paracetamol, ethanol, l-isoleucine, l-histidine, l-cysteine, dopamine, l-serine, l-tyrosine, phenylalanine, urea, hydrogen peroxide, K⁺, Ca²⁺, Na⁺, F^-, Cu²⁺, Fe³⁺, Zn²⁺, SO₄^2-, SO₃^2-, Cl^-, folic acid and ascorbic acid. The proposed electrochemical method was successfully applied to produce a sensor for the detection of 4-AP in juice and water samples.