Carbon Screen-Printed Electrode Coated with Poly (Toluidine blue) as an Electrochemical Sensor for the Detection of Tyramine ^†

In the present work the surface modification of a carbon screen-printed electrode by electrochemical polymerization of toluidine blue (TB) for determination of tyramine is described. The electrochemical polymerization of the electrode with TB was done by cyclic voltammetry at a scan rate of 50 mV/s and a potential sweep between ‒0.7 V and 1.0 V in the presence of 0.5 mM TB in an electrolyte solution. At each cycle, the polymer film started to deposit on the carbon screen-printed electrode which was repeated 20 times. For parameter optimization the electrochemical behavior of the modified electrode was analyzed by amperometric methods such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV). A phosphate buffer solution (PBS) was used as an electrolyte for all the amperometric experiments. The electrochemically modified poly-TB-coated carbon-screen-printed electrode showed an oxidation peak potential of tyramine at 0.67 V. The unmodified carbon-screen-printed electrode showed the tyramine oxidation peak potential at 0.9 V. Based on the voltammetric results, it was found that the poly-TB-modified carbon-screen-printed electrode showed higher sensitivity (1.78 µA nM⁻¹ cm⁻²) than a bare carbon-screen-printed electrode toward tyramine detection. Tyramine in 0.1 M PBS (pH 7.4) was analyzed by cyclic voltammetry from the potential of ‒0.7 to 1.0 V at a scan rate of 50 mV/s. The poly-TB-modified carbon-screen-printed electrode exhibited a linear response between catalytic peak current and tyramine concentration from 0.02 µM to 270.5 µM with a lower detection limit of 0.007 µM (S/N = 3).