Spectrophotometric Determination of Penicillamine in Penicillamine Tablets

Based on the reduction of Fe(Ⅲ) to Fe(Ⅱ) by penicillamine due to its sulfhydryl group and on the color reaction between the Fe(Ⅱ) ion and 2,2′-bipyridine to give a reddish orange colored complex with its absorption maximum at the wavelength of 524 nm, a spectrophotometric method for indirect determination of penicillamine in penicillamine tablets was proposed. The optimized conditions found were as follows: ① amount of 0.2 mol·L-1 HOAc-NaOAc buffer solution of pH 4.5: 2.5 mL; ② amount of 0.2 g·L-1 FeCl3 solution: 2 mL;③ amount of 1 g·L-1 2,2′-dipyridine solution: 2.5 mL; ④ time of reaction: 5 min. Linear relationship between values of absorbance and mass concentration of penicillamine was obtained (indirectly) in the range less than 26 mg·L-1, with detection limit (3S/N) of 0.01 mg·L-1. The proposed method was used in the analysis of penicillamine tablets, giving results of penicillamine contents in consistency with the labelled value with RSD (n=5) of 2.4%.