Synergistic Supramolecular Effect on the Electro-Oxidation of Biological Relevant Molecules: A Novel Sensor for Simultaneous Determination of Epinephrine and Uric Acid in Human Urine Using MWCNT and a Copper(II) Complex

Bruno Ferraz,Eliziana Gomes,André Formiga,Marcus Sousa,Juliano Bonacin,Eduardo De Arruda,Fernando Leite,Andréa Malagutti

doi:10.21577/0103-5053.20200154

Abstract

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.

Highlights

The bottom-up strategy is based on the concept of building blocks and is a central idea of Supramolecular Chemistry
The characterization of the unmodified multi-walled carbon nanotubes (MWCNTs) and [Cu(H2dimpy)Cl]PF6/MWCNT composite was performed by scanning electron microscopy (SEM) (Figures 1a and 1b) and energy dispersive spectroscopy (EDS) (Figures 1c and 1d)
The smallest semi-circle was observed when the glassy carbon electrode (GCE) surface was simultaneously modified with MWCNTs and [Cu(H2dimpy)Cl]PF6, and the Rct value decreased to 69.2 ± 0.7 Ω, proving that there is a synergistic effect on the electron transfer rate

Summary

Introduction

The analytical method was developed using square wave voltammetry (SWV) and its parameters (potential pulse amplitude, potential step increment and frequency) were optimized to assess the optimum experimental performance for the simultaneous determination of EP and UA with the [Cu(H2dimpy)Cl]PF6/MWCNTs/GCE. The smallest semi-circle was observed when the GCE surface was simultaneously modified with MWCNTs and [Cu(H2dimpy)Cl]PF6, and the Rct value decreased to 69.2 ± 0.7 Ω, proving that there is a synergistic effect on the electron transfer rate.

Results

Conclusion