Adsorption and Reduction of Berberine at a Mercury Electrode

Abstract

Adsorption and reduction of berberine are investigated by alternating current polarography and square-wave voltammetry in electrolytes of various pH. Both berberine and the product of its reduction canadine form condensed ®lms on the mercury electrode surface. These processes limit the analytical application of square-wave voltammetry combined with adsorptive accumulation of berberine. Reduction of berberine is totally irreversible and occurs between À0.95 V and À1.35 V, depending on berberine concentration and pH of solution. Canadine is electroinactive and can not be reoxidized on mercury electrode. Its condensed ®lm is very stable, even at À0.5 V, and may prevent adsorption of berberine. The properties of square-wave voltammetric responses of berberine in acidic, neutral and basic electrolytes are reported and the conditions for their electroanalytical application are discussed.

A theory of square-wave voltammetry of surface-active, electroinactive compounds

“…the degree of electrode surface coverage  m and the gradient dÂ/dt = ( m−1 −  m )/d were calculated using Eq. (12) or (20). The current was calculated at the end of each SW half-period (m = 25, 50, 75, .…”

“…In fact, the sensitivity of SWV to capacitive current depends on the frequency of signal, particularly in the case of electrode reactions complicated by the reactant adsorption [19]. Characteristic examples are adsorption and desorption peaks of berberine and canadine condensed on the mercury electrode surface [20]. These tensammetric peaks are comparable in magnitude to the faradaic peak of berberine reduction.…”

Electrochemistry of Mercury

“…Komorsky-Lovric [149] has investigated adsorption and reduction of the plant alkaloid berberine in electrolytes of various pH at mercury electrodes, applying ac polarography and square-wave voltammetry. Reduction of berberine appeared irreversible and occurred between −0.95 and −1.35 V, depending on the pH of the solution.…”

A selective and sensitive assay of berberine using total internal reflected resonance light scattering technique with fluorescein at the water/1,2-dichloroethane interface

“…In view of its widespread and important use, its quantification is important in pharmacological and clinical analysis [18,19]. In recent years, new techniques have been developed to determine the BE such as HPLC [20][21][22], self-ordered ring technique [23], voltammetric methods [24], potentionmetric sensor [25], and spectrophotometry [26,27]. However, these methods were limited in either complicated operation or sophisticated instrumentation, or poor selectivity.…”