Spectrophotometric studies were carried out to investigate the charge-transfer reaction between cinnarizine and dipicrylamine (DPA) or
2,6-dinitrophenol (DNP). Simple and rapid spectrophotometric methods were suggested for the determination of cinnarizine (CN) in pure
and in its pharmaceutical dosage forms. The colored products are quantified spectrophotometrically at 430 and 440 nm for cinnarizine
complexes with DPA in a mixture of 15% dioxane in dichloroethane (I) and 15% ethyl acetate in chloroform (II), respectively. On the other
hand, cinnarizine complexes formed with DNP in acetonitrile (III) and in a mixture of 30% dichloroethane in ethyl alcohol (IV) were
quantified at 460 and 430 nm, respectively. The proposed procedures were successfully utilized for the determination of the drug in its
pharmaceutical formulation using standard addition and calibration curve methods. Beer's law was obeyed in the concentration ranges 1.00-
22.00, 1.50-36.80, 1.50-36.80 and 3.60-36.80 µg mL-1 cinnarizine with molar absorpitivities of 1.64×104, 1.43×104, 5.16×104 and
3.60×104 (L mol-1 cm-1), for CN-DPA in mixture (I), CN-DPA in mixture (II), CN-DNP in acetonitrile (III) and CN-DNP in mixture (IV),
respectively. The relative standard deviations are less than 1.02%. The results of analysis of commercial tablets (Cinnarizine-25) showed
that there is no interference from any excipient. Statistical comparison of the results was performed with regard to accuracy and precision
using student's t-test and F-ratio at 95% confidence level.
Key words: Spectrophotometric determination, Cinnarizine, Charge-transfer complexes, Polynitrobenzene π-acceptors
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