Anodic stripping voltammetric determination of silver in anti-infective creams using carbon paste electrode

ABSTRACT

A new method for anodic stripping voltammetric determination of silver [I] using unmodified carbon paste electrode is described. In this method, the silver sample containing 10% phthalic acid solution is pre-concentrated on the electrode at -400 mV for 30 s. The deposited metal is then oxidized by anodic stripping voltammetric sweep. Chemical and electrical parameters affecting the voltammetric measurements are optimized. The peak current is proportional to the Ag [I] concentration over the range 0.5-50 ng/ml [r = 0.997], and the detection limit is 0.2-ng/ml. The relative standard deviation is 2% for 50 ng/ml [four replicates]. Satisfactory results are obtained on applying the proposed method to the determination of Ag [I] in digested samples of topical creams containing 1% silver sulphadiazine. No interference due to many cations is observed. In contrast, 10-fold excess of Cu ions has been shown serious interference, but on adding either 0.2 mM 4-[pyridyl-2-azo] resorcinol [PAR] or thiocyanate, the overlapped peaks can be separated into two well-defined peaks and consequently both cations, Ag and Cu can be determined simultaneously