Indirect Determination of Cimetidine by UV-Vis Spectrophotometry

A method for the indirect determination of cimetidine by UV-Vis spectrophotometry was established. Cu²⁺ solution was added to cimetidine sample solution, then the solution was adjusted to pH 7 with 0.1 mol·L^-1 sodium hydroxide solution and 0.1 mol·L^-1 hydrochloric acid solution, and kept the acidity with acetic acid-sodium acetate buffer solution (pH 7), and stable Cu²⁺-cimetidine complex was formed with an obvious characteristic absorption peak at 325 nm. The content of cimetidine was determined indirectly by measuring absorbance of the complex. Linear relationship between mass concentration of cimetidine and the absorbance of Cu²⁺-cimetidine complex system was kept in a definite range, with detection limit (3s/k) of 3.00 mg·L^-1. Recovery test was made on the actual samples by standard addition method at 3 concentration levels, giving recovery in the range of 95.3%-102%, and RSDs of the determined values (n=5) were ranged from 1.2% to 2.9%.