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Reversed-phase high performance liquid chromatography (LC) method is developed for the assay of sodium montelukast in coated tables and its photodegradation kinetics. An isocratic LC separation is performed on a Zorbax XDB C18 column using a mobile phase of acetonitrile-methanol-water (pH 3.8) (75:10:15, v/v/v) at a flow rate of 0.8 mL/min and detection at 280 nm. The detector response for sodium montelukast is linear over the concentration range from 5-35 μg/mL (r = 0.9999). The specificity of the method is proved using stress conditions. The solutions are exposed to UV radiation (352 nm), alkaline and acid hydrolysis, oxidation, and temperature (80 °C). The intra- and inter-day precision show suitable results (RSD < 0.49%). The accuracy of analytical method is 100.04% (RSD = 0.44%). Detection and quantification limits are 0.10 and 0.32 μg/mL respectively. The robustness of the method is assured after small changes in chromatographic conditions. The kinetic of photodegradation using a LC method is established and it can be described by zero-order kinetics. This developed method show to be viable for the determination of sodium montelukast in pharmaceutical dosage form and satisfactory in the determination of the kinetics of degradation.

A simple, accurate, and effective capillary electrophoresis method with ultraviolet absorbance detection was developed and validated for the quantitation of the antihistamine fexofenadine in capsules. The separation was performed with an uncoated fused-silica capillary (47 cm × 75 μm id) and was operated at 20 kV potential. Temperature was maintained at 25°C. The run buffer was prepared with 20mM Na2B4O7 × 10 H2O. Software was used for system control, data acquisition, and analysis. Method validation was performed by evaluation of the analytical parameters linearity, precision, accuracy, limits of detection and quantitation, and specificity. The method was linear (r = 0.9999) at concentrations ranging from 20 to 100 μg/mL, precise (relative standard deviation intra-assay = 1.2, 1.6, and 1.8% and interassay = 1.5%); accurate (recovery = 98.1%); and specific. The limits of detection and quantitation were 0.69 and 2.09 μg/mL, respectively. The method was compared to the liquid chromatography method developed previously by the authors for the same drug, and no significant difference was found between the 2 methods in fexofenadine hydrochloride quantitation.

This study describes the development and validation of a microbiological assay, applying the cylinder-plate method, for the determination of the antibiotic telithromycin. The microbiological method consisted of a cylinder-plate agar diffusion assay using Micrococcus luteus ATCC 9341 as the test microorganism. The response graphs for standard and sample solutions were linear (r = 0.9987), and no parallelism deviations were detected in the tested concentrations (0.25, 0.5, and 1.0 g/mL). The interday precision was 2.67%. Recovery values were between 96.75 and 100.91%. A preliminary stability study of telithromycin showed that the microbiological assay is specific for the determination of telithromycin in the presence of its degradation products. The proposed method allows the quantitation of telithromycin in pharmaceutical dosage form and can be used for drug analysis in routine quality control.