Poly(3,4-ethylene-dioxythiophene) electrode for the selective determination of dopamine in presence of sodium dodecyl sulfate

A novel biosensor using poly(3,4-ethylene dioxythiophene) (PEDOT) modified Pt electrode was developed for selective determination of dopamine (DA) in presence of high concentrations of ascorbic acid (AA) and uric acid (UA) with a maximum molar ratio of 1/1000, and 1/100 in the presence of sodium dodecyl sulfate (SDS). SDS forms a monolayer on PEDOT surface with a high density of negatively charged end directed outside the electrode. The electrochemical response of dopamine was improved by SDS due to the enhanced accumulation of protonated dopamine via electrostatic interactions. The common overlapped oxidation peaks of AA, UA and DA can be resolved by using SDS as the DA current signal increases while the corresponding signals for AA and UA are quenched. The use of SDS in the electrochemical determination of dopamine using linear sweep voltammetry at modified electrode PEDOT/Pt resulted in detecting dopamine at relatively lower concentrations. The DA concentration could be measured in the linear range of 0.5 to 25 μmol L^? 1 and 30 μmol L^? 1 to 0.1 mmol L^? 1 with correlation coefficients of 0.998 and 0.993 and detection limits 61 nmol L^? 1 and 86 nmol L^? 1, respectively. The validity of using this method in the determination of dopamine in human urine was also demonstrated.