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á351ñASSAY FOR STEROIDS
The following procedure is applicable for determination of those Pharmacopeial steroids that possess reducing functional groups such as a-ketols.
Standard Preparation— Dissolve in alcohol a suitable quantity of the USP Reference Standard specified in the individual monograph,previously dried under the conditions specified in the individual monograph and accurately weighed,and dilute quantitatively and stepwise with alcohol to obtain a solution having a concentration of about 10µg per mL.Pipet 20mLof this solution into a glass-stoppered,50-mLconical flask. Assay Preparation— Prepare as directed in the individual monograph. Procedure— To each of the two flasks containing the Assay Preparationand the Standard Preparation,respectively,and to a similar flask containing 20.0mLof alcohol to serve as the blank,add 2.0mLof a solution prepared by dissolving 50mg of blue tetrazolium in 10mLof methanol,and mix.Then to each flask add 2.0mLof a mixture of alcohol and tetramethylammonium hydroxide TS(9:1),mix,and allow to stand in the dark for 90minutes.Without delay,concomitantly determine the absorbances of the solutions from the Assay Preparationand the Standard Preparationat about 525nm,with a suitable spectrophotometer,against the blank.Calculate the result by the formula given in the individual monograph,in which Cis the concentration,in µg per mL,of the Reference Standard in the Standard Preparation;and AUand ASare the absorbances of the solutions from the Assay Preparationand the Standard Preparation,respectively. |