Stability-indicating methods for determination of vincamine in presence of its degradation product.

Three different stability indicating assay methods are developed and validated for determination of vincamine in the presence of its degradation product (vincaminic acid). The first method is based on the derivative ratio zero crossing spectrophotometric technique using 0.1 N hydrochloric acid as a solvent. In the second method, measurements are based on spectro-densitometric technique using high performance thin-layer chromatography (HPTLC) plates with a developing system consisting of methanol-chloroform-ethyl acetate (2:1:1, v/v/v). The third method depends on high-performance liquid chromatography (HPLC). Separation of vincamine from vincaminic acid using Lichrocart RP-18 column (250 mm x 4.6 mm i.d.) with a mobile phase consisting of acetonitrile-ammonium carbonate (0.01 M) (7:3, v/v) is achieved. The methods showed high sensitivity with good linearity over the concentration ranges of 12 to 48 microg ml-1, 3 to 17 microg/spot, and 2 to 20 microg ml-1 for derivative spectrophotometry, spectro-densitometry and HPLC methods, respectively. The developed methods were successfully applied to the analysis of pharmaceutical formulations containing vincamine with excellent recoveries.

Colorimetric and fluorimetric methods for determination of panthenol in cosmetic and pharmaceutical formulation.

Two methods are suggested for determination of panthenol. The first is colorimetric method where panthenol is subjected to alkaline hydrolysis; the resulting beta-alanol is allowed to react with vanillin (Duquenois reagent) in presence of McIlvain buffer pH 7.5. The color developed is measured at 406 nm. The linearity range was found to be 50-500 microg/ml while the lower limit of detection was about 10 microg/ml. The second is a sensitive and reliable modified fluorimetric method is also suggested, whereas panthenol, after alkaline hydrolysis is treated with ninhydrin. The fluorescent product was found to have excitation lambda(max) at 385 nm and emission lambda(max) at 465 nm. The method showed high sensitivity with linearity range from 0.01 to 3 microg/ml. The lower limit of detection (LOQ) reached 0.005 microg/ml. Validation of both methods was carried out and the two methods were applied for determination of panthenol in some cosmetic and pharmaceutical formulations.