Voltammetric behaviour of levodopa and its quantification in pharmaceuticals using a beta-cyclodextrine doped poly(2,5-diaminobenzenesulfonic acid) modified electrode

A cyclic voltammetric method based on a beta-cyclodextrine doped poly(2,5-diaminobenzenesulfonic acid) modified glassy carbon electrode (GCE) was developed for the determination of levodopa. Compared with bare GCE and poly(2,5-diaminobenzenestilfonic acid)/GCE, the poly(2,5-diaminobenzenesulfonic acid)-beta-cyclodextrine/GCE exhibits a remarkable shift of the oxidation potentials of levodopa in the cathodic direction and a drastic enhancement of the anodic current response. The incorporation of beta-cyclodextrine into the polymer film exhibited that the electrode provides more stable and sensitive current responses for levodopa. Levodopa exhibited a single broad peak at about 0.6 V at bare GCE. However, at the beta-cyclodextrine doped poly(2,5-diaminobenzenesulfonic acid)/GCE, a well-defined redox wave of levodopa was obtained, with the oxidation and the reduction peak potential at 0.193 and 0.164 V, respectively. The separation of peak potentials was 29 mV. The linear current response was obtained in the range of 1.0 x 10(-6) similar to 2.0 x 10(-4) M with a detection limit of 4.18 x 10(-7) M for levodopa, The poly(2,5-diaminobenzenesulfonic acid)-beta-cyclodextrine/GCE was also effective to simultaneously detect levodopa and ascorbic acid. The modified electrode has been successfully applied for the determination of levodopa in pharmaceuticals. The poly(2,5-diaminobenzenesulfonic acid)-beta-cyclodextrine/GCE showed excellent stability and reproducibility.