Validated High-Performance Thin-Layer Chromatographic Method for the Evaluation of Oseltamivir Pharmaceutical Formulations Counterfeited with Ascorbic Acid Compared with a Colorimetric Method

A selective high-performance thin-layer chromatographic (HPTLC) method has been established for the quantitative determination of oseltamivir phosphate (OST) without interference of ascorbic acid (ASC) added to some of its counterfeit pharmaceutical formulations. Chromatographic separation was performed on precoated silica gel 60 GF(254) plates with methanol-water-ammonia 6:4:0.05 (v/v) as mobile phase at ambient temperature. The developed plates were scanned and quantified at 254 nm. Experimental conditions such as band size, mobile phase volume, chamber saturation time, migration of solvent front, etc. were critically studied, and the optimum conditions were selected. A satisfactory resolution was obtained with R-F 0.70 and 0.83 for OST and ASC, respectively. Also, HPTLC-band detection method has been established for rapid qualitative assay of OST using ninhydrin spray. On the other hand, a colorimetric method has been established using bromocresol green (BCG) as rapid, accurate, and selective comparative method. Both methods were validated for linearity, accuracy, precision, selectivity, and specificity. The calibration plots were linear between 5.00 and 14.00 mu g band(-1) and 6.00-18.00 mu gmL(-1) for the HPTLC and colorimetric methods, respectively. The detection limits were 1.80 mu g band(-1) and 2.00 mu g mL(-1), for the HPTLC and colorimetric methods, respectively. The simplicity of the proposed methods suggest its application in quality control analysis of OST in its capsules and granules for oral suspension.