A method with high sensitivity, good accuracy and fast response is of ever increasing importance for the simultaneous detection of AA, DA and UA. In this paper, a simple and sensitive electrochemical sensor, which based on the polyvinylpyrrolidone (PVP)-graphene composite film modified glassy carbon electrode (PVP-GR/GCE), was presented for detecting ascorbic acid (AA), dopamine (DA) and uric acid (UA) simultaneously. The PVP-GR/GCE has excellent electrocatalytic activity for the oxidation of AA, DA and UA. The second-order derivative linear sweep voltammetry was used for the electrochemical measurements. The peak potential differences of DA-AA, DA-UA, and UA-AA (measured on the PVP-GR/GCE) were 212, 130 and 342 mV respectively. Besides, the over potential of AA, DA and UA reduced obviously, so did the peak current increase. Under the optimum conditions, the linear ranges of AA, DA and UA were 4.0 μM-1.0 mM, 0.02-100 μM, and 0.04-100 μM, respectively. The detection limits were 0.8 μM, 0.002 μM and 0.02 μM for AA, DA, and UA. The electrochemical sensor presented the advantages of high sensitivity and selectivity, excellent reproducibility and long-term stability. Furthermore, the sensor was successfully applied to the analysis of real samples.

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Porous gold nanosheets modified glassy carbon electrode (GCE) was facilely prepared by one-step electrodeposition, using N-methylimidazole as a growth-directing agent. The porous gold nanosheets modified GCE was characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction spectroscopy. The modified electrode displayed improved sensitivity for individual and simultaneous differential pulse voltammetric determination of dopamine (DA; at 180 mV) and acetaminophen (AC; at 450 mV vs. Ag/AgCl) even in the presence of ascorbic acid. The oxidation peak currents linearly increased with the concentrations of DA and AC in the ranges from 2.0 to 298.0 μM and 3.0 to 320.0 μM, respectively, and the detection limits are 0.28 μM for DA and 0.23 μM for AC. The relative standard deviations (n=20) are 1.5 % for DA and 0.4 % for AC.

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