Abstract
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•Four spectrophotometric methods for determination of cinnarizine and dimenhydrinate.•They can be used for analysis of binary mixtures with severely overlapped spectra.•They have equal accuracy, precision compared to chromatographic methods.•Ratio difference does not need fixed wavelengths or any derivative calculation.•Constant center method predicts the UV spectra of each single drug.
Four simple, specific, accurate and precise spectrophotometric methods are developed and validated for simultaneous determination of cinnarizine (CIN) and dimenhydrinate (DIM) in a binary mixture with overlapping spectra, without preliminary separation. The first method is dual wavelength spectrophotometry (DW), the second is a ratio difference spectrophotometric one (RD) which measures the difference in amplitudes between 250 and 270nm of ratio spectrum, the third one is novel constant center spectrophotometric method (CC) and the fourth method is mean centering of ratio spectra (MCR). The calibration curve is linear over the concentration range of 4–20 and 10–45μg/ml for CIN and DIM, respectively. These methods are tested by analyzing synthetic mixtures of the above drugs and they are applied to commercial pharmaceutical preparation of the subjected drugs. The validity of results was assessed by applying standard addition technique. The results obtained were found to agree statistically with those obtained by a reported method, showing no significant difference with respect to accuracy and precision.