Abstract A simple and sensitive spectrophotometric method is described for the assay of cimetidine. Modern analytical technique for cimetidine in various dosage forms are limited by cost and absence of high technological equipment especially in the third World countries including Nigeria. The research investigates the use of charge transfer complexation in the spectrophotometric assay of cimetidine as an alternative method to conventional methods. Spectrophotometer was employed to determine charge transfer complex formation between cimetidine (n- donor) and chloranilic acid (π-aceptor) in 1,4- dioxan. The developed method was employed in the assay of commercial cimetidine in solid dosage forms. The wavelength of maximum absorption (λmax) of the complex was at 254 nm compared to 315 nm for π-acceptor alone. Chloranilic acid was found to form a charge-transfer complex in a 1:1 stoichiometry. Conformity with Beer’s law was evident over the concentration range 1.260 x 10-3 to 12.60 mg %. A detailed investigation of the complex formed was made with respect to its composition, association constant and molar absorptivity. This method has been applied successfully to the analysis of commercially available cimetidine tablet with good recovery (99.90 ± 1.20 %) and reproducibility.
Keyword: Spectrophotometer; Chloranilic acid; Cimetidine; Stoichiometry; Maximum absorption.