Epinephrine sensing at nanostructured Au electrode and determination its oxidative metabolism

Epinephrine (EP) is a neurotransmitter and hormone involved in an enormous number of processes in living organisms, however its highly active oxidation metabolites can cause hard damages and lead to serious health consequences. This paper described a relatively simple method of fabrication of Au nanotube array electrodes for electrochemical determination of EP, which could be easily transferred to non-laboratory conditions. On the basis of Tafel plot, some parameters of EP oxidation process like number of electrons involved in the rate-determining step (n(alpha) = 2) and electron transfer coefficient (alpha =0.45) were evaluated for the studied electrode. The linear sweep voltammetry (LSV) revealed a very good linear response in the EP concentration range of 60-600 mu M EP, however to 1000 mu M its linearity differs insignificantly. Using differential pulse voltammetry (DPV), the calibration curve for EP determination is close to linear in the range of 10-150 mu M, but the detection limit of 2.8 mu M was evaluated for a lower concentration range 10-60 mu M. The proposed DPV method was successfully applied to the determination of EP in a pure, ascorbic acid containing and real samples. The DPV results were evaluated and compared with those obtained by the high-performance liquid chromatography (HPLC) method. Combining the ROXYTM EC System with mass spectrometry creates an analytical tool for oxidative products of EP and conjugation of EP reactive potential metabolites characterized for I and II stage of biotransformation. The presence of leucoadrenochrome-o-semiquinone radicals confirmed by mass spectrometry implies that the ECE (electron transfer-chemical reaction-electron transfer) mechanism of EP oxidation at the Au electrode is more feasible. (C) 2016 Elsevier B.V. All rights reserved.