The Interference of Ascorbic Acid in Sensitive Detection of Dopamine by a Non- Oxidative Sensing Approach

Determination of Dopamine electrochemically by direct oxidation is difficult due to the co-oxidation of ascorbic acid present in high concentration in biological fluids in the same potential window. In this report, we present a non oxidative approach to electrochemically detect dopamine with high selectivity and sensitivity using our newly developed poly (anilineboronic acid ) composite with single walled carbon nanotubes. The mechanism of interference by ascorbic acid was studied and the results showed that ascorbic acid interacted with poly (anilineboronic acid) both chemically and electrocatalytically due to its multifunctional diol motif. An association constant between ascorbic acid and phenylboronic acid was determined to quantitate the strength of the interaction between the two molecules. By depositing a layer of permselective ionomer Nafion on top of the composite, the sensor can selectively detect dopamine in pM~ nm range. The high sensitivity along with the improved selectivity of this approach might have potential application toward molecular diagnosis of Parkinson's disease.