Voltammetric determination of catechol and hydroquinone using nitrogen-doped multiwalled carbon nanotubes modified with nickel nanoparticles

Nitrogen-doped multiwalled carbon nanotubes modified with nickel nanoparticles (Ni/N-MWCNT) were prepared by a thermal reduction process starting from urea and Ni(II) salt in an inert atmosphere. The nanocomposite was deposited on a screen printed electrode and characterized by X-ray diffraction, scanning and transmission electron microscopy, nitrogen adsorption, X-ray photoelectron spectroscopy, and thermogravimetric analyses. The performance of the composite was investigated by cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The numerous active metal sites with fast electron transfer properties result in enhanced electrocatalytic activity towards the individual and simultaneous detection of catechol (CC) and hydroquinone (HQ), best at 0.21 V for CC and 0.11 V for HQ (vs. Ag/AgCl). For both targets the detection limit (S/N of 3) was 9 nM (CC) and 11 nM (HQ), and the Ni/N-MWCNT-electrode showed linear response from 0.1-300 mu M CC, and 0.3-300 mu M HQ. The electrode is selective over many potentially interfering ions. It was applied to the analysis of spiked water samples and gave satisfactory recoveries. It also is sensitive for CC (5.396 mu A center dot mu M-1 cm(-2)) and HQ (5.1577 mu A center dot mu M-1 cm(-2)), highly active, durable, acceptably repeatable and highly reproducible.