Spectrophotometric determination of dextromethorphan hydrobromide in pure form and in pharmaceutical formulations

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

Utility of certain pi-acceptors for the spectrophotometric determination of some skeletal muscle relaxants and antihistamine drugs

Three pi-acceptors, p-chloranilic acid [PCA], 2,3-dichloro-5,6-dicyano-p-benzoquinone [DDQ] and tetracyanoquinodimethane [TCNQ], have been used for the assay of some drugs of pharmaceutical interest. The studied drugs were orphenadrine citrate [1], baclofen [2], acrivastine [3] and tizanidine hydrochloride [4]. The assay is based on the fact that, the drugs under test are electron donors and react with p-CA, DDQ and TCNQ forming charge transfer complexes having intense absorption bands in the visible region of the spectrum. The colored products had absorption maxima at 530, 457 and 842nm for p-CA, DDQ and TCNQ respectively. The different experimental parameters were studied and incorporated in the procedure. For p-CA, Beer's law was obeyed in the concentration ranges [40-280], [20-140], [20-200] and [40-600] microg/ml for 1, 2, 3 and 4 respectively. For DDQ, Beer's law was obeyed from [20-140], [30-90] and [10-200] microg/ml for 1, 2 and 4 respectively. For TCNQ, Beer's law was obeyed in the concentration ranges [5-50], [1-15], [1.25-11.25] and [5-17.5] microg/ml for 1, 2 ,3 and 4 respectively. The procedure was favorably applied for determination of certain pharmaceutical dosage forms containing the studied drugs. The obtained results from tablets assays were found of good accuracy [t-test] and reproducibility [F-test]. The obtained results were also compared to the official and reported ones. There no significant differences were found between the proposed and the official or reported methods