Foreign steroids Present in steroidal drugs

Materials Required Silica gel G mobile-phase (1, 2-dichloroethane methanol water 95 5 0.2) 100 ml mixture of chloroform and methanol (9 1) 50 ml solution (1) betamethasone valerate sample 1. 5% w/v solution (2) betamethasone valerate BPCRS/EPCRS 1.5% w/v solution (3) a solution containing 0.030% w/v each of betamethasone EPCRS and betamethasone 21-valerate BPCRS alkaline tetrazolium blue solution q.s.  

Procedure Apply separately to the coated TLC plate 1 pi of each of three solutions (1), (2) and (3) prepared in a mixture of chloroform/methanol stated above. After removal of the plate, allow it to cool dry in air until the solvents have evaporated, heat at 105 °C for 10 minutes, cool and spray with alkaline tetrazolium blue solution. 

Observations (1) The principal spot in the chromatogram obtained with soln. (1) corresponds in position, colour and intensity to that obtained with soln. (2), 

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