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An isocratic reversed-phase high-performance liquid chromatographic method has been developed and validated for the simultaneous determination of aspirin, prasugrel HCl and clopidogrel bisulfate in the presence of clopidogrel-related compound (impurity-A) in focus on counterfeit. This method was used to determine counterfeited antiplatelet drugs in two substandard Indian pharmaceutical products sold on the market in Yemen and two traditional herbal medicines sold on the market in China. Thin layer chromatography and mass spectrometry of counterfeit herbal medicines have additionally been carried out to verify the identification of adulterants. Chromatographic separation was performed on Inertsil ® ODS-3 C18 (4.6 × 250 mm, 5 μm) with isocratic mobile phase elution containing a mixture of acetonitrile: (25 mM) potassium dihydrogen phosphate buffer, pH 2.7 adjusted with 0.1 M o -phosphoric acid (79: 21, v/v), at a flow rate of 1 mL/min and UV detection at 220 nm. Designs of experiment methodology, Plackett–Burman and Box–Behnken designs were used for the screening and optimization of the mobile phase composition. The method validation was also performed in accordance with the International Council on Harmonization (ICH) guidelines. The method developed for routine analysis was found to be sensitive, simple, accurate and highly robust. The results were statistically compared to reference methods using Student's t -test and variance ratio F -test at P  < 0.05. [ABSTRACT FROM AUTHOR]

The article discusses the results of simultaneous determination of chlorzoxane and ketoprofen in binary mixtures and in ternary mixtures containing the chlorzoxane degradation product by reversed-phase liquid chromatography (LC). The analytes were separated by LC on a Lichrosphere 60 C18 columns. The mobile phases satisfactorily resolved the binary and ternary mixtures.

The article describes column liquid chromatography and thin-layer chromatography-densitometry methods for simultaneous determination of acediasulfone and cinchocaine. The optimized methofs proved to be specific and accurate for the analysis of the cited drugs in laboratory-prepared mixtures and dosage forms.

A fixed dose combination of enalapril maleate (EN) and nitrendipine (NT) achieved satisfactory blood pressure control rather than monotherapy. Four accurate spectrophotometric methods utilizing ratio spectra were developed and validated for the simultaneous determination of EN and NT in combined pharmaceutical dosage form (Eneas® tablets). The first method was first derivative ratio spectrophotometric method (1DD) where the amplitudes maxima were measured at 219.2 nm and 233.4 nm for the determination of EN and NT, respectively. The second method was ratio difference spectrophotometric method where EN and NT were estimated by measuring the amplitudes difference between 213 nm and 225 nm on the ratio spectrum of EN and between 241 nm and 227 nm on the ratio spectrum of NT. The third method was ratio subtraction followed by extended ratio subtraction, EN was determined at 210 nm by subtraction of the constant values from the ratio spectrum then multiplication with the divisor (NT spectrum). An extended ratio subtraction method was then applied in order to determine NT at 235 nm by using the zero-order spectrum of EN (10 μg/ml) as a divisor. The fourth method was ratio subtraction coupled with constant multiplication methods. The zero- order absorption spectrum of the laboratory prepared mixture was divided by NT (12 μg/ml) spectrum, subsequently, the value of the constant was multiplied by the divisor to obtain the original spectrum of NT, followed by its subtraction from the laboratory prepared mixture to get the spectrum of EN. EN and NT were determined at 210 nm and 235 nm, respectively. Linearity was ascertained over the concentration ranges of (1–11 μg/ml) for EN and (2–14 μg/ml) for NT, for the first and second methods and (2–13 μg/ml) for EN and (3–20 μg/ml) of NT, for the third and fourth methods. Application of the methods to the determination of the cited drugs in Eneas® tablets gave satisfactory results. Methods validation confirmed their accuracy and selectivity. Statistical comparison of the results with the reported one showed no significant difference, regarding precision and accuracy. Routine analysis of the cited drugs in quality control laboratories could be performed using the developed methods. Unlabelled Image • Resolution of overlapped spectra of enalapril and nitrendipine • Application of first derivative ratio, ratio subtraction and ratio difference methods • Recently developed extended ratio subtraction and constant multiplication methods were successfully applied. • Analysis of Eneas® tablets without prior separation [ABSTRACT FROM AUTHOR]

An isocratic reversed - phase high performance liquid chromatographic method has been developed and validated to simultaneously determine nicotinic acid, pravastatin sodium, rosuvastatin calcium, atorvastatin calcium, pitavastatin calcium, lovastatin sodium and simvastatin sodium in focus on counterfeit drug detection. Thin-layer chromatography, nuclear magnetic resonance and mass spectrometry have been additionally performed to verify the identification of adulterants of counterfeit herbal medicines. Chromatographic separation was carried out on Inertsil® ODS-3 C18 (4.6 × 150 mm, 5 μm) with isocratic mobile phase elution containing a mixture of acetonitrile: methanol: 25 mM potassium dihydrogen phosphate buffer, pH 2.86 adjusted with 0.1 M o -phosphoric acid (48: 30: 22, v/v / v), at a flow rate of 1 mL/min and with UV detection at 238 nm. The design of experiment methodology, Plackett–Burman and Box–Behnken designs, was used to screen and optimize the mobile phase composition. The validation of the method was also carried out under the International Conference on Harmonization guidelines. The developed method was sensitive, accurate, simple, economical and highly robust, in addition to the comprehensiveness and novelty of this method for separating the seven drugs. The results were statistically compared with the reference methods used Student's t -test and variance ratio F -test at P  < 0.05. [ABSTRACT FROM AUTHOR]