A multi-walled carbon nanotube/poly-2,6-dichlorophenolindophenol film modified carbon paste electrode for the amperometric determination of l-tyrosine

A novel multi-walled carbon nanotube/poly-2,6-dichlorophenolindophenol (DCPIP) film modified carbon paste electrode (MCPE/MWCNTs/p-DCPIP) was constructed using drop casting and electropolymerization methods. Cyclic voltammetry and amperometric techniques were employed for the determination of l-tyrosine (Tyr). An electrochemically induced oxa-Michael addition reaction has been proposed as a possible mechanism of the electropolymerization of DCPIP on the surface of the modified electrode. The surface morphology and interface properties of the electrodes were investigated by FE-SEM images and the electrochemical impedance spectroscopy (EIS), respectively. The AFM images confirm the formation of nano fibrous deposits of DCPIP. The spectroelectrochemical study performed reveals the structural changes in Tyr during oxidation. This sensor was used for the selective detection of Tyr at physiological pH in the presence of some common interfering biomolecules. Chronoamperometic technique was employed for the determination of the diffusion coefficient and the standard heterogeneous electron transfer rate constant (k₀) of Tyr at the modified electrode. The sensor exhibited a linear response to Tyr over a wide concentration range of 0.3 μM-8.0 μM and 10.0 μM-110.0 μM with a detection limit (70.5 ± 2.35) nM (S/N = 3). The practical utility of the sensor was demonstrated by determining Tyr in spiked human blood serum and soya sauce.