In this paper a novel supramolecular strategy to improve the efficiency of a voltammetric sensor to determine two biologically relevant molecules (epinephrine (EP) and uric acid (UA)) is presented. The strategy is based on the use of a glassy carbon electrode modified with a copper(II) complex ([Cu(H2dimpy)Cl]PF6) adsorbed on multi-walled carbon nanotubes (MWCNTs). The [Cu(H2dimpy)Cl]PF6/MWCNT composite-supported electrode was characterized by electrochemical impedance spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The electrocatalytic oxidation of EP and UA using the sensor was investigated by cyclic voltammetry and square wave voltammetry. Under optimized conditions, voltammetric peak currents showed a linear response for the EP and UA concentrations in the ranges 0.5-159.2 and 0.2-58.5 µmol L−1, whereas the limits of detection were 0.2 and 0.05 µmol L−1, respectively. The sensor was successfully applied in the selective and simultaneous determination of EP and UA in human urine samples. Thus, our results showed that the supramolecular strategy was successful to build an efficient sensor for simultaneous detection of these molecules in biological samples.

This work reports a simple and low cost voltammetric approach comprising a boron-doped diamond electrode (BDDE) to determine the antibiotic ethionamide (ETO). Cyclic voltammetry studies revealed that ETO exhibits an irreversible reduction peak at -0.95 V and an irreversible oxidation peak at +1.4 V onto BDDE (vs. saturated Ag/AgCl reference electrode) in Britton-Robinson buffer solution (pH 5.0, 0.1 mol L-1). Different voltammetric scan rates (from 10 to 150 mV s-1) suggested that the reduction of ETO on the BDDE surface is a diffusion-controlled process. Square wave voltammetry (SWV) optimized conditions showed a linear response to ETO from 1.00 to 80.0 µmol L-1 (R2 = 0.998) with a limit of detection of 0.294 µmol L-1 and limit of quantification of 0.980 µmol L-1. The developed square wave voltammetric method was successfully used in the determination of ETO in human urine and pharmaceutical formulation. The ETO quantification results in pharmaceutical tablets obtained by SWV-BDDE were comparable to those found by official analytical protocols.