A: Place a portion of the contents of Capsules,equivalent to about 50mg of diazoxide,in a suitable centrifuge tube,add 25mLof 0.1Nsodium hydroxide,shake for 15minutes,and centrifuge:the supernatant so obtained responds to the Thin-layer Chromatographic Identification Test á201ñ,a solvent system consisting of a mixture of ethyl acetate,methanol,and ammonium hydroxide (17:4:3)being used.

B: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that of the Standard preparation,both relative to the internal standard,as obtained in the Assay.

Medium: pH6.8phosphate buffer (see under Buffer Solutionsin the section Reagents,Indicators,and Solutions);900mL.

Apparatus 1: 100rpm.

Time: 45minutes.

Procedure— Determine the amount of C8H7ClN2O2Sdissolved from UVabsorbances at the wavelength of maximum absorbance at about 268nm of filtered portions of the solution under test in comparison with a solution of USP Diazoxide RSsimilarly prepared.

Tolerances— Not less than 75%(Q)of the labeled amount of C8H7ClN2O2Sis dissolved in 45minutes.

Mobile phase,Internal standard solution,Standard preparation,andChromatographic system— Prepare as directed in the Assayunder Diazoxide.

Assay preparation— Remove,as completely as possible,the contents of not less than 20Capsules,and weigh accurately.Mix the combined contents,and transfer an accurately weighed quantity of the powder,equivalent to about 100mg of diazoxide,to a 100-mLvolumetric flask,add 15mLof water,and shake by mechanical means for 5minutes.Add 60mLof methanol,shake by mechanical means for 15minutes,dilute with methanol to volume,and mix.Transfer 5.0mLof this solution to a 100-mLvolumetric flask,add 2.0mLof Internal standard solution,dilute with a mixture of water and methanol (4:1)to volume,and mix.

Procedure— Proceed as directed for Procedurein the Assayunder Diazoxide.Calculate the quantity,in mg,of C8H7ClN2O2Sin the portion of Capsules taken by the formula: in which Cis the concentration,in µg per mL,of USP Diazoxide RSin the Standard preparation,and RUand RSare the peak response ratios obtained from the Assay preparationand the Standard preparation,respectively.