Electrocatalytical properties of bergenin on a multi-wall carbon nanotubes modified carbon paste electrode and its determination in tablets

The electrocatalytic oxidation of bergenin is investigated on the surface of the multi-wall carbon nanotubes (MWCNT) modified carbon paste electrode (CPE) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Using the modified electrode, the kinetics of the electrooxidation of bergenin is considerably enhanced, by lowering the anodic overpotential through a catalytic effect. In the following anodic sweep from 0.1 to 0.9 V, bergenin adsorbed at MWCNT modified CPE surface yielded a sensitive oxidation peak at 0.614 V. The anodic peak potential (E-pa) shifts negatively of 135 mV when compared with that on bare CPE. Due to its unique structure and extraordinary properties, MWCNT shows higher electrocatalytic efficiency toward bergenin. A linear dynamic range of 6.0 x 10(-7) to 1.0 x 10(-5) M for bergenin is obtained in phosphate buffer solutions (PBS) of pH 7.0, the linear regression equation is expressed as I-pa (mu A) = 0.0430c (mu M) + 0.0318, r=0.9989 and the detection limit is 7.0 x 10(-8) M after 3 min open-circuit accumulation. The relative standard deviation of 1.0 x 10(-6) M bergenin in 10 successive scans is 1.6% for the same electrode and 2.0% for interelectrodes, indicating excellent reproducibility. The modified electrode exhibited a high stability when it was placed in dry state. No loss of electroactivity of the electrode was found for the continuous cyclical sweep for 6 h and the modified electrode was also not deteriorated even for 3 weeks. The influence of various interferences on the response of 1 mu m bergenin presented a small signal change. Bergenin has been successfully detected in tablets and the recovery ranges from 99.8% to 100.2%. High sensitivity and selectivity together with low detection limit of the electrode response make it very suitable for the determination of trace amounts of bergenin in pharmaceutical and clinical preparations. (C) 2007 Published by Elsevier B.V.