Abstract

A new nanocomposite based on nitrogen-doped graphene nanosheets/CuCo<inf>2</inf>O<inf>4</inf> nanoparticles was prepared and used as an electrode material for simultaneous determination of dopamine, melatonin and tryptophan. For this purpose, CuCo<inf>2</inf>O<inf>4</inf> nanoparticles were supported on porous nitrogen-doped graphene nanosheets by a simple method. The nanocomposite was characterized by transmission electron microscopy and X-ray diffraction spectroscopy. Incorporation of the prepared nanocomposite in a carbon paste electrode (CPE) increased the oxidation peak currents and reduced the overpotential of dopamine, melatonin and tryptophan. The new developed sensor was then employed for the simultaneous determination of target analytes with linear ranges of 0.010-3.0 μM, using differential pulse voltammetry. Detection limits of 0.0033, 0.0049 and 0.0041 μM were achieved for dopamine, melatonin and tryptophan, respectively. The selectivity of the method was studied and the results showed that the fabricated sensor is free from interference of organic compounds especially uric acid and ascorbic acid. Finally, the proposed electrochemical sensor was employed to determine analytes in urine, serum and pharmaceutical samples. © The Royal Society of Chemistry 2015.