A: Transfer to a centrifuge tube a quantity of powdered Tablets,equivalent to about 500mg of metyrapone,add 10mLof 1Nsodium hydroxide,and mix.Extract with 10mLof chloroform,centrifuge,and filter:the IRabsorption spectrum of this solution,determined in a 0.5-mm cell against chloroform,exhibits maxima only at the same wavelengths as that of a similar solution of USP Metyrapone RS.

B: Transfer to a centrifuge tube 1mLof the filtrate obtained in Identificationtest A,add 20mLof chloroform,and extract with 30mLof 1Nsulfuric acid,centrifuging and filtering the sulfuric acid layer through a pledget of cotton.Dilute 1mLof this solution with 1Nsulfuric acid to 100mL:the UVabsorption spectrum of the resulting solution exhibits maxima and minima at the same wavelengths as that of a similar solution of USP Metyrapone RS,concomitantly measured.

Medium: 0.1Nhydrochloric acid;900mL.

Apparatus 1: 100rpm.

Time: 45minutes.

Procedure— Determine the amount of C14H14N2Odissolved from UVabsorbances at the wavelength of maximum absorbance at about 259nm of filtered portions of the solution under test,suitably diluted with 0.1Nhydrochloric acid,in comparison with a Standard solution having a known concentration of USP Metyrapone RSin the same medium.

Tolerances— Not less than 60%(Q)of the labeled amount of C14H14N2Ois dissolved in 45minutes.

2 ,4-Dinitrophenylhydrazine in methanol—Shake by mechanical means about 1g of 2,4-dinitrophenylhydrazine with 75mLof methanol in a 100-mLflask for about 15minutes,and filter through paper.Prepare fresh daily.

2 ,4-Dinitrophenylhydrazine hydrochloride—Mix 2mLof hydrochloric acid with 23mLof 2,4-Dinitrophenylhydrazine in methanol.

Potassium hydroxide in methanol— Dissolve 5g of potassium hydroxide in 100mLof methanol,and filter.

Standard preparation— Dissolve an accurately weighed quantity of USP Metyrapone RSin chloroform,and dilute quantitatively and stepwise with chloroform to obtain a solution having a known concentration of about 100µg per mL.

Assay preparation— Weigh and finely powder not less than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 25mg of metyrapone,with the aid of 10mLof 1Nsodium hydroxide,to a centrifuge tube.Shake gently,and extract with three 15-mLportions of chloroform.Centrifuge each extract,filtering through a pledget of cotton,previously washed with chloroform,into a 50-mLvolumetric flask.Add chloroform to volume,and mix.Pipet 5mLof this solution into a 25-mLvolumetric flask,add chloroform to volume,and mix.

Procedure— Pipet 3mLeach of the Standard preparation,the Assay preparation,and chloroform to provide a blank,into separate 50-mLvolumetric flasks.To each flask add 1mLof 2,4-Dinitrophenylhydrazine hydrochloride,and shake lightly.Evaporate the solutions on a steam bath to near dryness.Wash down the sides of the flask with 1mLof chloroform and methanol (1:1),and again evaporate the solutions to near dryness.Heat the flasks in an oven maintained at 110to 120for 30minutes.Remove the flasks,pipet 10mLof Potassium hydroxide in methanolinto each flask,and heat again in the boiling water bath for 1minute.Allow to cool to room temperature,insert the stoppers,shake by mechanical means for 5minutes,add methanol to volume,and mix.Concomitantly determine the absorbances of the solutions in 1-cm cells relative to the blank,at the wavelength of maximum absorbance at about 450nm,with a suitable spectrophotometer.Calculate the quantity,in mg,of metyrapone (C14H14N2O)in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Metyrapone RSin the Standard preparation,and AUand ASare the absorbances of the solutions from the Assay preparationand the Standard preparation,respectively.