ABSTRACT
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