Hydrodynamic chronoamperometric determination of hydrogen peroxide using carbon paste electrodes coated by multiwalled carbon nanotubes decorated with MnO<inf>2</inf> or Pt particles

Abstract

© 2016 Elsevier B.V. All rights reserved. In this comparative study a traditional paraffin oil and graphite powder based carbon paste electrode (CPE) was surface modified with multiwalled carbon nanotubes (MWCNTs) and with composites of MnO2-MWCNT or Pt-MWCNT by drop coating method to prepare simply, sensitive and reliable voltammetric sensors either for the determination of H2O2 or after additional modification of the appropriate sensor surfaces with glucose oxidase (GOx) for the determination of glucose via H2O2 in selected samples. The scanning electron microscopic characterization in combination with energy dispersive X-ray spectrometry of the composite materials confirmed that the mediators, MnO2 and Pt particles, are randomly distributed on the surface of the MWCNTs, and represent nearly 5% (m: m) of the composites expressed as Pt and Mn. Cyclic voltammetric (CV) investigations were performed in acetate (pH 4.50), phosphate (pH 7.50) and borate (pH 9.18) buffers to characterize the basic electrochemical behaviors and to select the working potentials suitable for hydrodynamic chronoamperometric (HA) determination of H2O2 under different circumstances. The CV responses showed that in slightly alkaline media all investigated electrodes, i.e., CPEs unmodified and modified with plain MWCNTs and MWCNTs based composites are in principle applicable, but with different efficiency at different potentials, with favorable reduction and acceptable oxidation of H2O2 at the Pt-MWCNT/CPE and predominately oxidation at the MnO2-MWCNT/CPE. The reproducibility of the responses with the MnO2-MWCNT/CPE is poor, but can be improved by electrochemical conditioning. The latter one performed well in alkaline supporting electrolyte (pH 9.18), while in the case of the Pt-MWCNT/CPE the signals are much better established in slightly acidic medium (pH 4.50). The analytical methods were optimized, mainly with the Pt-MWCNT/CPE as the preferential electrode, in terms of pH and working potential for the HA determination of H2O2 in spiked milk samples including the development of an appropriate sample treatment procedure. This electrode was also used for the design of a very simple and reliable first generation oxidase biosensor for determination of glucose content in human infusion via its enzymatic reaction product H2O2.