Evaluation of the usefulness of a novel electrochemical sensor in detecting uric acid and dopamine in the presence of ascorbic acid using a screen-printed carbon electrode modified with single walled carbon nanotubes and ionic liquids

A novel sensor was developed in order to determine dopamine (DP) and uric acid (UA) by adsorptive voltammetry, using optimal amounts of single walled carbon nanotubes (SWCNT) dispersed in chitosan solution (cs) and deposited on a screen-printed carbon electrode (SPCE). The electrode surface (cs-SWCNT/SPCE) was treated with the ionic liquid (IL) 1 butyl-3-metilimidazolium tetrafluorborate (BMIMBP₄). The electro-catalytic properties of the cs-SWCNT-IL/SPCE were studied with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrode surface was studied using scanning electron microscopy (SEM). Anodic peak currents for DP and UA with BMIMBP₄ in the presence of ascorbic acid (AA) increased by 17.0 and 70.0% respectively. Optimal parameters were (pH 2.4; adsorption time; t_ADS 100s and adsorption potential; E_ADS -0.10 V). Anodic peak currents were proportional to the concentration between 0.5 and 5.0 μmol L⁻¹ using standard solutions of PD and UA respectively, and 0.50–30.0 μmol L⁻¹ for DP and 0.50–1000 μmol L⁻¹ for UA with real samples. Detection limits were 0.16 μmol L⁻¹ for DP and 0.17 μmol L⁻¹ for UA. The sensor was used in the determination of AU and DP in human urine samples spiked with quantities of DP with recovery between 85 and 102% for DA and UA respectively.