Determination of astemizole in pharmaceutical preparations using spectrophotometric methods

UV absorption and second derivative spectrophotometric methods were develop ed for the determination of astemizole in commercial pharmaceutical formula tions containing this compound alone. Solutions of astemizole in 0.1 M HCl: methanol (1:3) were used in the methods and the linearity range was 4.6-45. 8 mug ml(-1) in both methods. The mean recoveries and relative standard dev iations were calculated and the method was applied to two commercial prepar ations marketed in Turkey. Results were compared with the literature method , HPLC. Also, two new spectrophotometric methods are described for the simu ltaneous determination of astemizole and pseudoephedrine hydrochloride in t heir combination. In the first method, first derivative spectrophotometry, dA/d lambda values were read at selected wavelengths in zero-crossing point s in the first derivative spectra of the mixture solution in 0.1 M HCl:meth anol (1:3). In the second, ratio spectra derivative spectrophotometry, anal ytical signals were measured at the wavelengths corresponding to either max imums and minimums for both drugs in their solution in 0.1 M HCl:methanol ( 1:3) in the first derivative spectra of their ratio spectra. The procedures do not require any separation step. The mean recoveries were found satisfa ctory in the methods. (C) 2001 Elsevier Science B.V. All rights reserved.