Abstract: The electrochemical response of dopamine(DA) at a pyrocatechol sulfonephthalein modified glassy carbon(PS/GC) electrode is reported.The electrode can be used as a detector for the determination of dopamine with a high stability and a good sensitivity.The cyclic voltammetric results indicated that there was a couple of well-defined redox peaks for dopamine at the PS/GC electrode with E_pa= 220 mV, E_pc=95 mV and the formal potential E^o'= 157.5 mV(vs.SCE) at 100 mV/s in the buffer solution of pH 7.0.The PS/GC electrode can also be used to separate the electrochemical responses of ascorbic acid and DA by 54 mV with the differential pulse voltammetry.Under the selected conditions, the oxidation peak currents are linear with DA concetration in the range of 5.0 × 10^-6 to 5.0 × 10^-4 mol/L, and the detection limit is 1.0 ×10^-6 mol/L at S/N=3.Normalized with concentration, the relative sensitivity of dopamine to ascorbic acid reaches ca.30.8: 1.

Key words: Chemically modified electrode, Neurotransmitter, Dopamine, Ascorbic acid, Pyrocatechol sulfonephthalein