Curcumin-quinone immobilised carbon black modified electrode prepared by in-situ electrochemical oxidation of curcumin-phytonutrient for mediated oxidation and flow injection analysis of sulfide

Curcumin, a natural pigment of the turmeric, has been widely used as a phytonutrient for various health benefits. There are several electrochemical reports relating to curcumin-metal complex modified electrodes for electroanalytical applications, and sensing of curcumin utilising the electrochemical behaviour of the phenolic site using different carbon-based chemically modified electrodes, in the literature. Herein, we report, a curcumin-quinone (Cur-Q) derivative immobilised carbon black (CB) modified glassy carbon electrode, designated as GCE/CB@Cur-Q, prepared by an in-situ electrochemical oxidation method, for efficient electrocatalytic oxidation and electrochemical sensing application of sulfide in pH2 KCl-HCl solution. The “as prepared” GCE/CB@Cur-Q showed a sharp redox peak at an apparent standard electrode potential, Eo′=0.55V vs. Ag/AgCl with surface excess and peak-to-peak potential values of 12.37×10−9molcm−2 and 19±5mV respectively. No such electrochemical behaviour was noticed when unmodified GCE was subjected to the electrochemical oxidation of curcumin. The existence of Cur-Q was confirmed by Liquid chromatography-mass spectrometer and in-situ electrochemical quartz crystal microbalance measurements. Amongst various carbon materials like CB, multiwalled carbon nanotube (MWCNT), single-walled carbon nanotube, oxygen functionalized MWCNT, graphite nanopowder, graphitised mesoporous carbon, carbon nanofiber, graphene oxide and activated charcoal investigated, CB was showed an excellent electrochemical reaction for the in-situ formation of Cur-Q. A highly sensitive electrocatalytic oxidation and sensing by amperometric i-t and flow injection analysis of sulfide at operating potential, 0.55V vs. Ag/AgCl with detection limit values (signal-to-noise ratio=3) of 2.4×10−6 and 7.12×10−6M respectively, without any interference from other biochemicals like uric acid, dopamine, nitrite, cysteine, NADH and H2O2, unlike the conventional chemically modified electrodes with serious interferences, have been demonstrated. [Display omitted] •Curcumin-quinone surface-confined carbon black modified electrode was developed.•Molecular transformation of the curcumin was precisely identified using EQCM technique.•An efficient electro-catalytic oxidation of sulfide suitable for analytical application was shown.•Electrochemical flow injection analysis of sulfide was demonstrated.