Surface decoration of multi-walled carbon nanotubes modified carbon paste electrode with gold nanoparticles for electro-oxidation and sensitive determination of nitrite

• A new modified electrochemical sensor was constructed and used.
• Gold nanoparticles were simply decorated at the carbon paste electrode.
• The electrochemical properties of electrode were studied.
• This modifier enhanced the electrochemical properties of electrode.
• The electrode was used for the determination of nitrite in real samples.

In this paper, a highly sensitive and selective voltammetric sensor for the determination of nitrite is proposed. We described a fast and easy method for the fabrication of gold nanoparticles/multi-walled carbon nanotube/carbon paste electrode (GNPs /MWCPE) by one-step electrodeposition under controlled potential, the whole procedure takes only several minutes. Scanning electron microscopy (SEM) image demonstrated that the gold nanoparticles deposited on MWCNTs/CPE were uniform, with an average size of 30 nm. By combining the benefits of GNPs/MWCNTs and CPE, the resulted modified electrode exhibited outstanding electrocatalytic activity in terms of nitrite oxidation by giving much higher peak currents than those found for the unmodified CPE and also the MWCNTs-modified electrode. The effect of various experimental parameters on the voltammetric response of nitrite was investigated. At the optimum conditions the sensor has a linear response in the 0.05–250.0 µmol L−1 concentration range, a very good detection sensitivity (0.4177 μA L µmol−1), and a low detection limit of 1×10−2 μmol L−1 of nitrite. Most common ions and many environmental organic pollutants do not interfere. The proposed chemically modified electrode was used to the determination of NO2- in several foodstuffs and water samples and the results were found to be consistent with the values obtained by the Griess protocol.