Simultaneous electrochemical determination of dopamine and tryptophan using a TiO2-graphene/poly(4-aminobenzenesulfonic acid) composite film based platform

TiO2-graphene/4-aminobenzenesulfonic acid composite film modified glassy carbon electrode (TiO2-GR/4-ABSA/GCE) was first employed for the simultaneous determination of dopamine (DA) and tryptophan (Trp). TiO2-GR/4-ABSA/GCE displayed excellent electrochemical catalytic activities toward the redox of DA and Trp. The cathodic peaks potentials of DA and Trp decreased significantly and their cathodic current peaks increased dramatically at TiO2-GR/4-ABSA/GCE. Differential pulse voltammograms (DPV) was used for the simultaneous determination of DA and Trp in their dualistic mixture. The peak separation between DA and Trp was large up to 177 mV. The calibration curves for simultaneous determination of DA and Trp were obtained in the range of 1–400 μM. The detection limits (S/N = 3) were 0.1 μM and 0.3 μM for DA and Trp, respectively. The present method was applied to the determination of DA and Trp in human serum samples.