Use of adsorptive square-wave anodic stripping voltammetry at carbon paste electrode for the determination of amlodipine besylate in pharmaceutical preparations

The antihypertensive drug amlodipine has been characterized voltammetrically in a carbon paste electrode by means of anodic stripping voltammetry. An adsorptive stripping method in a carbon paste electrode for trace determination of amlodipine has been described. Cyclic voltammetric studies indicated the oxidation of amlodipine besylate at the electrode surface through a single two-electron irreversible step fundamentally controlled by adsorption. A study of the variation in the peak current with solution variables such as pH, ionic strength, concentration of amlodipine, possible interference, and instrumental variables, such as preconcentration time and accumulation potential, has resulted in the optimization of the oxidation signal for analytical purposes. By anodic adsorptive anodic stripping voltammetry, the calibration plot was linear in the range 9.9 x 10(-9) - 1.4 x 10(-7) M with a detection limit of 2 x 10(-10) M in a carbon paste electrode at pH 11.0. The procedure was successfully applied to the assay of amlodipine besylate in some commercial products in the market (AmlopresA (R), Amlodipine, and NorvascA (R)). The percentage recoveries were in agreement with those obtained by the reference method.