A: Infrared Absorption 197K —Prepare the test specimen as follows. Transfer about 150 mg to a suitable separator, dissolve in 10 mL of water, and add 15 mL of 3 N hydrochloric acid. Extract with three 20-mL portions of chloroform, filter the extracts through anhydrous sodium sulfate, and collect the extracts in a suitable beaker. Evaporate the combined chloroform extracts on a steam bath with the aid of a current of air to dryness, and dry the residue at 105 for 2 hours.

B:Ultraviolet Absorption 197U—

C: Ignite about 100 mg: the residue responds to the tests for Sodium 191.

Standard solutions— Dissolve a quantity of USP Butabarbital RS in a mixture of chloroform and methanol (1:1) to obtain a solution having a final concentration of 4.0 mg per mL (Standard solution A). Dilute 1.0 mL of Standard solution A with a mixture of chloroform and methanol (1:1) to 10.0 mL, and mix (Standard solution B).

Test solution —Dissolve a quantity of Butabarbital Sodium in a mixture of chloroform and methanol (1:1) to obtain a solution having a final concentration of 44 mg per mL.

Procedure —Apply 10 µL of the Test solution and 10 µL each of Standard solution A and Standard solution B to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture. Develop the chromatogram in a solvent system consisting of a mixture of acetone, methylene chloride, methanol, and ammonium hydroxide (5:3:1:1) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, and dry the plate in a current of air. Spray the plate with a solution of mercurous nitrate dihydrate in 0.15 N nitric acid (1 in 100), and immediately estimate the intensities of any spots in the chromatogram of the Test solution, other than the principal spot, in comparison with Standard solution B: the RF value of the principal spot obtained from the Test solution corresponds to that obtained from Standard solution A; and the sum of the intensities of any secondary spots observed in the chromatogram of the Test solution is not greater than the intensity of the principal spot produced by Standard solution B, corresponding to not more than a total of 1% of impurities.

Standard preparation— Transfer about 25 mg of USP Butabarbital RS, accurately weighed, to a 200-mL volumetric flask, dissolve in pH 9.6 alkaline borate buffer (see under Buffer Solutions in the section Reagents, Indicators, and Solutions), and dilute with the same solvent to volume.

Assay preparation —Transfer about 28 mg of Butabarbital Sodium, accurately weighed, to a 200-mL volumetric flask, dissolve in pH 9.6 alkaline borate buffer to volume, and dilute with the same solvent to volume.

Procedure— Transfer 10.0 mL each of the Standard preparation and the Assay preparation to separate 100-mL volumetric flasks, dilute each with pH 9.6 alkaline borate buffer to volume, and mix. Concomitantly determine the absorbances of the solutions at the wavelength of maximum absorbance at about 240 nm, with a suitable spectrophotometer, using pH 9.6 alkaline borate buffer as the blank. Calculate the quantity, in mg, of C10H15N2NaO3 in the portion of Butabarbital Sodium taken by the formula: in which 234.23 and 212.25 are the molecular weights of butabarbital sodium and butabarbital, respectively; C is the concentration, in µg per mL, of USP Butabarbital RS in the Standard preparation; and AU and AS are the absorbances of the solutions from the Assay preparation and the Standard preparation, respectively.