A chemically modified carbon paste electrode (CPE) founded on electrospun manganese oxide (Mn3O4) nanofibers (MONFs) was constructed as a new simple electrochemical sensor for a sensitive simultaneous determination of dopamine (DA) and tyrosine (Tyr). To investigate their electrochemical behavior several methods like differential pulse voltammetry (DPV) and cyclic voltammetry (CV) methods were used. MONFs were fabricated by an electrospinning process by manganese acetate stabilized with polyvinyl alcohol (PVA) as the precursors. In order to characterize MONFs several techniques such as field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) technique and energy dispersive X-ray spectroscopy (EDX) were used. Application of MONFs as the modifier of the CPE (MONFs/CPE) showed high oxidation peak currents for determination of DA and Tyr due to its catalytic effect and its surface area. Optimization of experimental parameters, by DPV method, showed the best sensitivity in determination of DA and Tyr in phosphate buffer solution (PBS) at pH of 7 with accumulation time of 20 s. Using DPV technique, the sensor revealed broad linear ranges of 0.05-180 μM and 0.1-270 μM with detection limits of 49 nM and 56 nM toward DA and Tyr, respectively. The fabricated sensor exposed excellent sensitivity, simplicity and high selectivity toward simultaneous determination of DA and Tyr. The analytical application of the sensor has been assessed for analysis of DA and Tyr in human blood serum and urine with acceptable results.
