A novel sodium dodecyl benzene sulfonate modified expanded graphite paste electrode for sensitive and selective determination of dopamine in the presence of ascorbic acid and uric acid.

A sensitive and selective method was developed for the electrochemical determination of dopamine by using a sodium dodecyl benzene sulfonate modified expanded graphite paste electrode (SDBS-EGPE). The SDBS-EGPE was prepared by mixing expanded graphite (EG) self-assembled with sodium dodecyl benzene sulfonate (SDBS) with solid paraffin. SDBS formed a monolayer on EG surface with a high density of negatively charged end. Compared with EGPE, SDBS-EGPE showed improved electrochemical response of dopamine (DA) due to the enhanced accumulation of protonated DA via electrostatic interactions between positively charged DA and negatively charged SDBS. Under optimal experimental conditions, the designed electrode exhibited wide linear responses to DA ranging from 0.5 μmol/L and 500 μmol/L with a low detection limit of 0.027 μmol/L at a signal-to-noise ratio of 3. The SDBS-EGPE showed a good reproducibility, stability and reusability. The SDBS-EGPE showed a high selectivity for DA in the presence of ascorbic acid (UA) and uric acid (AA) due to the electrostatic repulsions between negatively charged UA, AA and SDBS. The proposed electrode was successfully applied in the determination of DA in the commercial dopamine hydrochloride injection sample. [ABSTRACT FROM AUTHOR]