Development and validation of stability indicating TLC densitometric and spectrophotometric methods for determination of Clobetasol propionate

Two simple analytical techniques that manipulate the inherent spectroscopic properties of the drug differently were developed for Clobetasol propionate (CP) determination in the presence of its alkaline hydrolytic degradation products. The first method depends on TLC-densitometric determination of the UV-visualized bands after TLC separation of CP in the presence of its alkaline degradation products in its bulk and pharmaceutical formulation. Separation was performed on preactivated silica gel 60 F254 TLC plates using ethyl acetate:hexane:ammonia (5:5:0.2, by volume) as a developing system followed by scanning at 240 nm. Linear correlation was obtained in the range of 0.10-0.50 μg/band. The second method was ratio difference spectrophotometry. It was applied by measuring the difference in peak amplitude of the ratio spectra at 243.40 and 256.40 nm. The selectivity of both methods was checked by analyzing laboratory prepared mixtures containing different concentrations of CP and its alkaline degradation products. The methods were validated in compliance with ICH guidelines. The methods determined CP in its bulk powder with average percentage recoveries of 99.60% ± 1.09 and 99.44% ± 1.60 for densitometry and ratio difference, respectively. Both methods were successfully applied for quantification of CP in its commercial cream.