Electrochemical determination of sulfite and phenol using a carbon paste electrode modified with ionic liquids and graphene nanosheets: Application to determination of sulfite and phenol in real samples

• A novel modified graphene paste electrode was constructed.
• This electrode reduced the overpotential for oxidation of sulfite about 215 mV.
• This electrode was used for simultaneous determination of sulfite and phenol.

Benzoylferrocene was used to construct a modified-graphene paste electrode. Also, hydrophilic ionic liquid (n-hexyl-3-methylimidazolium hexafluoro phosphate) was used as a binder to prepare the modified electrode. The electro-oxidation of sulfite at the surface of the modified electrode was studied using electrochemical approaches. This modified electrode offers a considerable improvement in voltammetric sensitivity toward sulfite, compared to the bare electrode. Square wave voltammetry (SWV) exhibits a linear dynamic range from 5.0 × 10−8 to 2.5 × 10−4 M and a detection limit of 20.0 nM for sulfite. The diffusion coefficient and kinetic parameters (such as electron transfer coefficient and the heterogeneous rate constant) for sulfite oxidation were also determined. The prepared modified electrode exhibits a very good resolution between the voltammetric peaks of sulfite and phenol that makes it suitable for the detection of sulfite in the presence of phenol in real samples.