Nile blue electropolymerized in ternary deep eutectic solvent on carbon nanotube modified screen printed electrodes for hydroquinone and catechol determination

The ternary deep eutectic solvent composed of choline chloride, oxalic acid and ethylene glycol in a 1:2:2 M ratio was used for the potential cycling electropolymerization of Nile blue (NB) on screen-printed electrodes (SPE) modified with carboxylate functionalized multiwalled carbon nanotubes (MWCNT). Nitric acid was used as acid dopant in the electropolymerization solution. The PNB/MWCNT/SPE modified electrode was characterized by cyclic voltammetry electrochemical impedance spectroscopy in 0.1 M Britton-Robinson buffer at pH 5.0 and the morphology by SEM. It was employed as sensor for the simultaneous determination of hydroquinone and catechol by differential pulse voltammetry in 0.1 M phosphate buffer saline at pH 7.0 in the concentration range 2 μM - 100 μM, with limits of detection of 0.10 and 0.09 μM for hydroquinone and catechol, respectively. The portable screen-printed sensor demonstrated good repeatability, reproducibility, sensitivity and was successfully applied to pharmaceutical formulations, natural and synthetic urine and tap water, being appropriate for future application outside the laboratory in the health and environmental contexts. • Screen printed electrodes modified with carbon nanotubes (MWCNT) and poly(Nile blue) (PNB) films. • Evaluation of ternary deep eutectic solvents for electropolymerization of Nile blue. • Electrochemical and microscopy characterization of PNB/MWCNT modified electrodes. • PNB-based electrochemical sensor for simultaneous quantification of hydroquinone and catechol. • Application to pharmaceutical formulations, natural and synthetic urine and tap water.