A: Triturate a quantity of finely powdered Tablets,equivalent to about 60mg of phenobarbital,with 50mLof chloroform,and filter.Evaporate the clear filtrate to dryness,and dry at 105for 2hours:the residue so obtained responds to Identificationtest Aunder Phenobarbital.

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: water;900mL.

Apparatus 2: 50rpm.

Time: 45minutes.

Procedure— Determine the amount of C12H12N2O3dissolved from UVabsorbances at the wavelength of maximum absorbance at about 240nm on filtered portions of the solution under test,suitably diluted with pH9.6alkaline borate buffer (see Buffer Solutionsin the section Reagents,Indicators,and Solutions),in comparison with a Standard solution having a known concentration of USP Phenobarbital RSin the same Medium.

Tolerances— Not less than 75%(Q)of the labeled amount of C12H12N2O3is dissolved in 45minutes.

pH4.5Buffer solution,Mobile phase,Internal standard solution,Standard preparation,and Chromatographic system— Prepare as directed in the Assayunder Phenobarbital.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Weigh accurately a portion of the powder,equivalent to about 20mg of phenobarbital,add 15.0mLof Internal standard solution,mix,and sonicate for 15minutes.Filter through a membrane filter having a 0.5-µm or finer porosity before use.

Procedure— Proceed as directed for Procedurein the Assayunder Phenobarbital.Calculate the quantity,in mg,of C12H12N2O3in the portion of Tablets taken by the formula: in which the terms are as defined therein.