Electropolymerization of brilliant cresyl blue in ethaline deep eutectic solvent on graphene quantum dot modified glassy carbon electrodes: Application to dipyrone determination

The binary deep eutectic solvent ethaline composed of choline chloride (ChCl) and ethylene glycol (EG) in a 1: 2 M ratio was used as solvent to carry out the electropolymerization of brilliant cresyl blue (BCB) on a glassy carbon electrode (GCE) modified with graphene quantum dots dispersed in chitosan plus Nafion (GQD chitosan+Nafion ) by potential cycling was investigated for the first time. Nitric acid was used as acid dopant in the electropolymerization solution. GQD chitosan was synthesized by a simple and ecofriendly procedure using citric acid as carbon source in a chitosan solution with 1 % v /v acetic acid. The PBCB/GQD chitosan+Nafion /GCE modified electrode was characterized by cyclic voltammetry, UV–vis spectroscopy, and fluorescence and the GQD chitosan by zeta potential measurements. The morphology of the synthesized polymer films was examined by scanning electron microscopy. The PBCB/GQD chitosan+Nafion /GCE sensor was employed for the determination of dipyrone by amperometry at a potential of +0.45 V vs. Ag/AgCl in the concentration range 15 μM - 225 μM, with a limit of detection of 1.3 μM, without interference from other analytes. The sensor demonstrated good repeatability, reproducibility, stability and was successfully applied with good recoveries for pharmaceutical formulations. • Brilliant cresyl blue (BCB) electropolymerized in ethaline deep eutectic solvent. • Modified electrodes with graphene quantum dots (GQD chitosan ) and PBCB polymer film. • GQD chitosan characterized by fluorescence and zeta potential. • GQD coated with chitosan and Nafion in optimized electrochemical sensors. • Sensors applied to amperometric determination of dipyrone in pharmaceutical samples.