Detection Of Norepinephrine Research Articles

A modified Hummers soft oxidative method for functionalization of CNTs: Preparation, characterization and potential application for selective determination of norepinephrine

Functionalized carbon nanotubes, CNTs(COOH), of excess oxygen containing functional groups were prepared using a modified Hummers method. The method is based on oxidizing pristine carbon nanotubes (P-CNTs) by moderately concentrated sulfuric acid and potassium permanganate at low temperature to avoid possible CNTs fragmentation and to preserve the aspect dimensional ratio. The resulting compatible materials were characterized and confirmed by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and electrochemical method including cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Fabrication of a sensitive sensor was much reliable by directly casting of CNTs(COOH) onto the surface of a glassy carbon electrode, CNTs(COOH)-GCE, rather than the tradition electrochemically reduced deposition method, ER-CNTs(COOH)-GCE, which ultimately misplaces large number of surface oxides. The functionalized surface materials exhibited an exceptional electrochemical activity on norepinephrine (NOR) oxidation in the presence of high concentrations of electrochemical active interference species such as ascorbic acid (AA) and uric acid (UA). The proposed sensor was excellently passed the selectivity test and lowered the detection limit of NOR (DL3σ, NOR) into 0.035 μM (6 ppb). It was also applied successfully for detection of NOR in serum blood sample with tolerable recovery percentages.

A Surface Network Based on Reduced Graphene Oxide/Gold Nanoparticles for Selective Determination of Norepinephrine in Real Samples

A spontaneous modification of glassy carbon electrode (GCE) by reduced graphene oxide (rGO) doped peripherally with gold nanoparticles (AuNPs) was fabricated and characterized by cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS). The electron transfer kinetics of surface materials was evaluated by fitting the charge transfer resistance (Rct) data in the presence of a redox probe such as [Fe(CN)6]3−/4−. The developed sensor (AuNPs.rGO-GCE) exhibited a large enhancement on the electrochemical oxidation of norepinephrine (NOR) than other arrays of surface assemblies. The voltammetric behavior of NOR at the present (AuNPs.rGO-GCE) modified surface was confirmed to follow a quazi-reversible reaction mechanism. Moreover, the apparent diffusion coefficient (Dapp) and the heterogeneous rate constant (ks) parameters of NOR species were collectively calculated using the classical irreversible electrochemical theory. The sensor showed excellent sensitivity and selectivity on NOR quantification in the presence of large concentration of ascorbic acid (AA) and the limit of detection of NOR (DL3σ) is lowered to 57 nM (10 ppb). The analytical performance of the proposed system was validated successfully for pharmaceutical (injection ampoule) and biological (plasma blood) samples with tolerable recovery percentages.