A: Dissolve a portion of the contents of Capsules, equivalent to about 50 mg of secobarbital sodium, in 10 mL of water, and filter into a separator. Add 2 mL of 3 N hydrochloric acid, extract the liberated secobarbital with 20 mL of chloroform, and evaporate the extract to dryness: the IR absorption spectrum of a 1 in 20 solution 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 500 mg of secobarbital sodium: the residue so obtained responds to the tests for Sodium 191.

Medium: water; 500 mL.

Apparatus 1: 100 rpm.

Time: 60 minutes.

Procedure— Determine the amount of C12H17N2NaO3 dissolved from UV absorbances at the wavelength of maximum absorbance at about 243 nm of filtered portions of the solution under test, mixed with sufficient sodium hydroxide to provide a concentration of 0.1 N sodium hydroxide, and suitably diluted with Dissolution Medium, if necessary, in comparison with a Standard solution having a known concentration of USP Secobarbital RS in 0.1 N sodium hydroxide.

Tolerances— Not less than 75% (Q) of the labeled amount of C12H17N2NaO3 is dissolved in 60 minutes.

Procedure for content uniformity— Transfer the contents of 1 Capsule to a 250-mL volumetric flask, with the aid of about 5 mL of alcohol. Add 10 mL of freshly prepared dilute ammonium hydroxide (1 in 200), and without delay dilute with the same solution to volume. Mix, filter if necessary, and discard the first 20 mL of filtrate. Dilute a portion of the clear solution with dilute ammonium hydroxide (1 in 200) to obtain a solution having a concentration of about 10 µg of secobarbital sodium per mL. Dissolve a suitable quantity of USP Secobarbital RS in dilute ammonium hydroxide (1 in 200) to obtain a Standard solution having a known concentration of about 10 µg per mL. Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 240 nm, with a suitable spectrophotometer, using dilute ammonium hydroxide (1 in 200) as the blank. Calculate the quantity, in mg, of C12H17N2NaO3 in the Capsule taken by the formula: in which 260.27 and 238.28 are the molecular weights of secobarbital sodium and secobarbital, respectively, T is the labeled quantity, in mg, of secobarbital sodium in the Capsule, CU is 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, CS is the concentration, in µg per mL, of USP Secobarbital RS in the Standard solution, and AU and AS are the absorbances of the solution from the Capsule contents and the Standard solution, respectively.

(Official January 1, 2007)

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 0.8 mg per mL.

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

Assay preparation— Weigh not less than 20 Capsules, 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 100 mg of secobarbital sodium, to a separator. Add 15 mL of water, 1 mL of hydrochloric acid, and 100 mL of chloroform, and shake for 3 minutes. Filter a portion of the chloroform layer through about 15 g of anhydrous sodium sulfate that is supported on a funnel by a small pledget of glass wool, combine 2.0 mL of this solution with 2.0 mL internal standard solution in a suitable container, and reduce the volume to about 2 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 secobarbital and butabarbital being not less than 3.0. [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 C12H17N2NaO3 in the portion of Capsules taken by the formula: in which 260.27 and 238.28 are the molecular weights of secobarbital sodium and secobarbital, respectively, and the other terms are as defined therein.