A: Dissolve a portion of the contents of Capsules,equivalent to about 50mg of secobarbital sodium,in 10mLof water,and filter into a separator.Add 2mLof 3Nhydrochloric acid,extract the liberated secobarbital with 20mLof chloroform,and evaporate the extract to dryness:the IRabsorption spectrum of a 1in 20solution of the residue in chloroform exhibits maxima only at the same wavelengths as that of a similar preparation of USP Secobarbital RS.

B: Ignite a portion of the contents of Capsules,equivalent to about 500mg of secobarbital sodium:the residue so obtained responds to the tests for Sodium á191ñ.

Medium: water;500mL.

Apparatus 1: 100rpm.

Time: 60minutes.

Procedure— Determine the amount of C12H17N2NaO3dissolved from UVabsorbances at the wavelength of maximum absorbance at about 243nm of filtered portions of the solution under test,mixed with sufficient sodium hydroxide to provide a concentration of 0.1Nsodium hydroxide,and suitably diluted with Dissolution Medium,if necessary,in comparison with a Standard solution having a known concentration of USP Secobarbital RSin 0.1Nsodium hydroxide.

Tolerances— Not less than 75%(Q)of the labeled amount of C12H17N2NaO3is dissolved in 60minutes.

Procedure for content uniformity— Transfer the contents of 1Capsule to a 250-mLvolumetric flask,with the aid of about 5mLof alcohol.Add 10mLof freshly prepared dilute ammonium hydroxide (1in 200),and without delay dilute with the same solution to volume.Mix,filter if necessary,and discard the first 20mLof filtrate.Dilute a portion of the clear solution with dilute ammonium hydroxide (1in 200)to obtain a solution having a concentration of about 10µg of secobarbital sodium per mL.Dissolve a suitable quantity of USP Secobarbital RSin dilute ammonium hydroxide (1in 200)to obtain a Standard solution having a known concentration of about 10µg per mL.Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 240nm,with a suitable spectrophotometer,using dilute ammonium hydroxide (1in 200)as the blank.Calculate the quantity,in mg,of C12H17N2NaO3in the Capsule taken by the formula: in which 260.27and 238.28are the molecular weights of secobarbital sodium and secobarbital,respectively,Tis the labeled quantity,in mg,of secobarbital sodium in the Capsule,CUis the concentration,in µg per mL,of secobarbital sodium in the solution from the Capsule contents,on the basis of the labeled quantity per Capsule and the extent of dilution,CSis the concentration,in µg per mL,of USP Secobarbital RSin the Standard solution,and AUand ASare the absorbances of the solution from the Capsule contents and the Standard solution,respectively.

Internal standard— Butabarbital.

Internal standard solution— Dissolve an accurately weighed quantity of Butabarbital in chloroform,and dilute quantitatively with chloroform to obtain a solution having a known concentration of about 0.8mg per mL.

Standard preparation— Dissolve accurately weighed quantities of USP Secobarbital RSand Butabarbital in chloroform,and dilute quantitatively with chloroform to obtain a solution that contains,in each mL,known amounts of about 0.9mg of USP Secobarbital RSand about 0.8mg of Butabarbital.

Assay preparation— Weigh not less than 20Capsules,and transfer the contents as completely as possible to a suitable container.Remove any residual powder from the empty capsules with the aid of a current of air,and weigh the capsule shells,determining the weight of the contents by difference.Mix the contents of the Capsules,and transfer an accurately weighed portion of the powder,equivalent to about 100mg of secobarbital sodium,to a separator.Add 15mLof water,1mLof hydrochloric acid,and 100mLof chloroform,and shake for 3minutes.Filter a portion of the chloroform layer through about 15g of anhydrous sodium sulfate that is supported on a funnel by a small pledget of glass wool,combine 2.0mLof this solution with 2.0mLinternal standard solution in a suitable container,and reduce the volume to about 2mLby evaporation,with the aid of a stream of dry nitrogen,at room temperature.

Chromatographic system and System suitability—Proceed as directed for Chromatographic Systemand System Suitabilityunder Barbiturate Assay á361ñ,the resolution,R,between secobarbital and butabarbital being not less than 3.0.[NOTE—Relative retention times are,approximately,0.6for butabarbital and 1.0for secobarbital.]

Procedure— Proceed as directed for Procedureunder Barbiturate Assay á361ñ.Calculate the quantity,in mg,of C12H17N2NaO3in the portion of Capsules taken by the formula: in which 260.27and 238.28are the molecular weights of secobarbital sodium and secobarbital,respectively,and the other terms are as defined therein.