A: Transfer a volume of Injection,equivalent to about 100mg of secobarbital sodium,to a separator containing 15mLof water.Render the mixture distinctly acid to litmus with hydrochloric acid,extract the liberated secobarbital with 25mLof ether,collect the ether extract in a separator,and wash with 10mLof water.Discard the water solution.Filter the ether extract into a beaker,and evaporate on a steam bath with the aid of a current of air just to dryness.Dissolve the residue in 3mLof alcohol,and evaporate to dryness.Repeat the dissolution and evaporation with 3mLof alcohol,and dry the residue at 100for 2hours:the IRabsorption spectrum of a solution prepared by dissolving the residue of secobarbital so obtained in chloroform to a concentration of about 50mg per mL,0.1-mm sodium chloride cells being used and chloroform being used as the blank,exhibits maxima only at the same wavelengths as that of a similar preparation of USP Secobarbital RS.

B: It responds to the flame test for Sodium á191ñ.

Buffer solution— Dissolve 6.19g of boric acid and 14.91g of potassium chloride in water,dilute with water to 200mL,and mix.After 24hours,filter if necessary to obtain a clear solution.

Standard preparation 1— Dissolve a suitable quantity of USP Secobarbital RS,accurately weighed,in 0.5Nsodium hydroxide to obtain a solution having a known concentration of about 23µg per mL.

Standard preparation 2— Mix 5.0mLof Standard preparation 1with 5.0mLof Buffer solution.

Assay preparation 1— Transfer an accurately measured volume of Injection,equivalent to about 50mg of secobarbital sodium,to a 100-mLvolumetric flask,dilute with 0.5Nsodium hydroxide to volume,and mix.Pipet 5mLof this solution into a 100-mLvolumetric flask,add 0.5Nsodium hydroxide to volume,and mix.

Assay preparation 2— Mix 5.0mLof Assay preparation 1with 5.0mLof Buffer solution.

Procedure— Concomitantly determine the absorbances of Assay preparation 1and Standard preparation 1in 1-cm cells at 260nm,with a suitable spectrophotometer,using 0.5Nsodium hydroxide as the blank.Similarly determine the absorbances of Assay preparation 2and Standard preparation 2,using as the blank a mixture of equal volumes of 0.5Nsodium hydroxide and Buffer solution.Calculate the quantity,in mg,of C12H17N2NaO3in the volume of Injection taken by the formula: in which 1.092is the ratio of the molecular weight of sodium secobarbital to that of secobarbital,Cis the concentration,in µg per mL,of USP Secobarbital RSin Standard preparation 1,AUand ASare the absorbances of Assay preparation 1and Standard preparation 1,respectively,and aUand aSare the absorbances of Assay preparation 2and Standard preparation 2,respectively.