Revaluation of the Determination Method for Related Substances in Cimetidine

OBJECTIVE To revalue the determination method for related substances in cimetidine. METHODS The related substances in cimetidine were tested by TLC and HPLC, respectively. The HPLC method was carried out on a C18 column with the mixture of methanol-water(240∶760) (dissolved 0.3 mL of phosphoric acid and 0.94 g sodium hexanesulfonate in 1 000 mL methanol) as mobile phase and UV wavelength at 220 nm. RESULTS The results of related substances tested by TLC were all within 0.5% in 8 batches of cimetidine from 7 manufacturers, but only one batch was within 0.5% by HPLC. CONCLUSION The result of related substances in cimetidine tested by HPLC was more credible than the result tested by TLC.