The influence of uric and ascorbic acid on the electrochemical detection of dopamine using graphene-modified electrodes

In this paper, we report on the preparation of gold electrodes modified with graphene-AuAg (Au/Gr-AuAg) or graphene-Au (Au/Gr-Au) composite materials as electrochemical sensors for dopamine (DA) detection. The response of the Au/Gr-AuAg electrode to dopamine was linear within a 3 × 10−7–3 × 10−4 M concentration range, and the Limit of Detection was found to be 2.05 × 10−7 M (S/N = 3). In contrast, the Au/Gr-Au electrode exhibited a narrower linear range (10−5–10−4 M) and a higher Limit of Detection (3.03 × 10−5 M). Using the Au/Gr-AuAg modified electrode, we have investigated the effect of two interfering species (ascorbic and uric acid), which are considered to be the most problematic species, due to the fact that their oxidation potentials are close to that of dopamine. Their presence in the electrolyte induced no shift in the peak potential of dopamine (+ 0.24 V) but instead led to an increase in the peak current. Consequently, a change in the calibration plot has occurred most probably due to the regeneration of dopamine under the influence of ascorbic acid. In that case, the Limit of Detection was found to be 2.16 × 10−6 M.