RESUMEN
Clobetasol propionate is an internationally accepted common name for 21-chloro-9-fluoro-11beta,17-dihydroxy16beta-methylpregna-1,4-diene-3,20-dione 17-propionate. The combination of calcipotriol (vitamin D3 analogue) andclobetasol propionate (super potent steroid) is being used as a topical formulation for the treatment of psoriasis fromseveral years. In this work, an ultra-high performance liquid chromatography equipped with photodiode array detectorand a mass compatible mobile phase in a gradient elution is employed for the separation of five related substancesin presence of calcipotriol and its two impurities with a last eluting impurity in less than 11 minutes. A simple andefficient sample extraction procedure was developed to achieve the highest sensitivity as of today with limit of detectionand limit of quantitation of 0.03% and 0.10%, respectively, as required by industry for drug product of clobetasolpropionate and its combination products. Stationary phase with fused core particle technology is employed for theseparation of impurities. Precision of the method is found to be less than 1.0% Relative standard deviation (RSD). Thecorrelation coefficient is >0.999. Accuracy of method is ranged from 93.3% to 108.0%. This is the first reported Ultrahigh performance liquid chromatography (UHPLC) method for the estimation of five related substances of clobetasolpropionate in its combination product with calcipotriol.