Erk Nevin
Department of Analytical Chemistry, Faculty of Pharmacy, University of Ankara, 06100 Ankara, Turkey.
J Pharm Biomed Anal. 2002 Apr 15;28(2):391-7. doi: 10.1016/s0731-7085(01)00627-6.
Two-component mixtures of dorzolamide hydrochloride and timolol maleate were assayed by first derivative and ratio derivative spectrophotometric methods. The first method, derivative spectrophotometry, by the zero-crossing measurements, was used due to the drugs closely overlapping absorption spectra. Linear calibration graphs of first derivative values at 250.3 nm for dorzolamide hydrochloride and 315.8 nm for timolol maleate. The second method, is based on ratio first derivative spectrophotometry, the amplitudes in the first derivative of the ratio spectra at 242.9 and at 223.5 nm were selected to determine dorzolamide and timolol maleate in the binary mixture. Calibration graphs were established for 8.0-30.0 microg ml(-1) for dorzolamide hydrochloride and 3.0-24.6 microg ml(-1) for timolol maleate in binary mixture. Good linearity, precision and selectivity were found, and the proposed methods were applied successfully to the pharmaceutical dosage from containing the above-mentioned drug combination without any interference by the excipients. Vierordt's method was also developed for a comparison method.
采用一阶导数分光光度法和比率导数分光光度法对盐酸多佐胺和马来酸噻吗洛尔的两组分混合物进行了测定。第一种方法，即导数分光光度法，由于两种药物的吸收光谱严重重叠，采用零交叉测量法。得到了盐酸多佐胺在250.3 nm处和马来酸噻吗洛尔在315.8 nm处的一阶导数值的线性校准曲线。第二种方法基于比率一阶导数分光光度法，选择比率光谱在242.9 nm和223.5 nm处的一阶导数幅度来测定二元混合物中的盐酸多佐胺和马来酸噻吗洛尔。建立了二元混合物中盐酸多佐胺8.0 - 30.0 μg ml⁻¹和马来酸噻吗洛尔3.0 - 24.6 μg ml⁻¹的校准曲线。结果表明该方法具有良好的线性、精密度和选择性，所提出的方法成功应用于含有上述药物组合的药物剂型，且不受辅料的干扰。还开发了维尔德特法作为比较方法。
