Identification, Infrared Absorption 
197K
—
Prepare the test specimen as follows. Place a volume of Oral Solution, equivalent to about 150 mg of butabarbital sodium, in a separator, render it distinctly alkaline by the addition of 1 N sodium hydroxide, and saturate it with sodium chloride. Extract the mixture with two 15-mL portions of ether, and discard the ether. Acidify the solution with hydrochloric acid, and render it just alkaline to litmus by adding small portions of sodium bicarbonate (carbonate-free). Extract the liberated acid barbiturate, using five 20-mL portions of chloroform. Wash the combined chloroform extracts with 10 mL of water acidified with 1 drop of hydrochloric acid, then extract the water with 10 mL of chloroform, adding the latter to the main chloroform solution. Filter the chloroform solution through a pledget of cotton or other suitable filter, previously washed with chloroform, into a tared beaker, and finally wash the separator and the filter with three 5-mL portions of chloroform. Evaporate the combined chloroform solution and washings on a steam bath with the aid of a current of air to dryness, and dry the residue at 105
for 2 hours.
Assay—
Internal standard solution—
Dissolve an accurately weighed quantity of secobarbital in chloroform, and quantitatively dilute with chloroform to obtain a solution having a known concentration of about 0.7 mg per mL.
Standard preparation—
Dissolve accurately weighed quantities of
USP Butabarbital RS and secobarbital in chloroform, and quantitatively dilute with chloroform to obtain a solution that contains, in each mL, known amounts of about 1 mg of
USP Butabarbital RS and about 1.4 mg of secobarbital.
Assay preparation—
[NOTE—This preparation includes a bromination step for elimination of parabens and a carbonate-chloroform extraction for elimination of benzoic acid.] Transfer an accurately measured volume of Oral Solution, equivalent to about 30 mg of butabarbital sodium, to a separator, add 1 mL of bromine water (prepared by dissolving 2.0 mL of bromine and 10 g of potassium bromide in 60 mL of water), and swirl. Allow to stand for 5 minutes, add 1 mL of sodium metabisulfite solution (1 in 10), and swirl. Add 300 mg of sodium bicarbonate in small portions, with mixing, and extract with four 10-mL portions of chloroform. Filter the extracts through about 15 g of anhydrous sodium sulfate that is supported on a funnel by a small pledget of glass wool. Collect the combined filtrates in a 50-mL volumetric flask, wash the sodium sulfate with 5 mL of chloroform, collecting the washing with the filtrate, dilute with chloroform to volume, and mix. Combine 2.0 mL of this solution with 2.0 mL of Internal standard solution in a suitable container, and reduce the volume to about 1 mL by evaporation, with the aid of a stream of dry nitrogen, at room temperature.
Chromatographic system and System suitability—
Proceed as directed for
Chromatographic System and
System Suitability under
Barbiturate Assay 361, the resolution,
R, between butabarbital and secobarbital being not less than 2.4.
[NOTE—Relative retention times are approximately 0.6 for butabarbital and 1.0 for secobarbital.
]
Procedure—
Proceed as directed for
Procedure under
Barbiturate Assay 361. Calculate the quantity, in mg, of butabarbital sodium (C
10H
15N
2NaO
3) in each mL of the Oral Solution taken by the formula:
(234.23 / 212.25)(50)(RU)(QS)(Ci) / V(RS),
in which 234.23 and 212.25 are the molecular weights of butabarbital sodium and butabarbital, respectively;
V is the volume, in mL, of Oral Solution taken; and the other terms are as defined therein.
Butabarbital Sodium Elixir