Simultaneous determination of L-cysteine and L-tyrosine using Au-nanoparticles/poly-eriochrome black T film modified glassy carbon electrode.

A novel Au-nanoparticles/poly-eriochrome black T film modified glassy carbon electrode (AuNPs/PEBT/GCE) was constructed for the simultaneous determination of l-cysteine (L-Cys) and l-tyrosine (L-Tyr) by differential pulse voltammetry. Fourier transform infrared spectra and electrochemical impedance spectroscopy indicate that the PEBT film was successfully polymerized on the surface of GCE and the film efficiently decreased the charge transfer resistance value of electrode and improved the electron transfer kinetic between analytes and electrode. The scanning electron microscope image shows that the immobilized AuNPs were spherical in shape and enhanced the electrical conductivity of PEBT film. In addition, PEBT film increased the oxidation currents of analytes four times when compared to bare GCE, and the AuNPs separated the oxidation potentials of L-Cys and L-Tyr by 488 mV while bare GCE failed to resolve them. The amperometry results exhibit that the electrocatalytic currents increased linearly with L-Cys concentrations in the range 0.05-100 μM (r=0.9981), and the detection limits of L-Cys and L-Tyr were 8 nM and 10 nM (S/N=3), respectively. With high sensitivity and selectivity, the proposed electrochemical sensor provides a simple method for simultaneous determination of L-Cys and L-Tyr.