RESUMO
Simple, sensitive and accurate spectrophotometric method have been developed for the determination of dextromethorphan hydrobromide in pure form and in pharmaceutical formulations. This method are based on the formation of ion-associate complexes between the drug and phenol red [I], cresol red [II], methyl orange [III], congo red [IV] and EBT [V] in acidic medium. The complexes are extracted into chloroform and measured at 407, 424 and 497 for [I or II], [III] and [IV] respectively, or into methylene chloride at 520 nm for [V]. Beer's law is obeyed in the concentration ranges from 2.0-24, 2.0-26 and 2.0-20 micro g ml[-1] for [I or II], [III or IV] and [V], respectively. The stoichiometric ratio of the ion-associate complexes was established using the continuous variation method and found to be 1:1 for all reagents used. The validity was assessed by applying the standard addition technique. The results were compared statistically with the official method showing a good agreement with high precision and accuracy