A: Suspend the contents of 1 Capsule in 10 mL of water, and filter: the filtrate responds to the flame test for Sodium 191.

B: The retention times of the major peaks in the chromatogram of the Assay preparation correspond to those of the Standard preparation obtained in the Assay.

Medium: water; 500 mL.

Apparatus 1: 100 rpm.

Time: 60 minutes.

Procedure— Determine the total amount of C12H17N2NaO3 and C11H17N2NaO3 dissolved from UV absorbances at the wavelength of maximum absorbance at about 239 nm of filtered portions of the solution under test, suitably diluted with 0.1 N sodium hydroxide, in comparison with a Standard solution having known concentrations of about 7.5 µg each per mL, of USP Secobarbital RS and USP Amobarbital RS in the same medium. An amount of alcohol not to exceed 1% of the total volume of the Standard solution may be used to dissolve the Reference Standards prior to dilution with water and 0.1 N sodium hydroxide.

Tolerances— Not less than 60% (Q) of the labeled total amount of C12H17N2NaO3 and C11H17N2NaO3 is dissolved in 60 minutes.

Internal standard solution— Dissolve aprobarbital in chloroform to obtain a solution having a concentration of about 0.75 mg per mL.

Standard preparation— Transfer about 92 mg of USP Secobarbital RS, and about 91 mg of USP Amobarbital RS, both accurately weighed, to a 100-mL volumetric flask, and dissolve in 50 mL of chloroform. Dilute with chloroform to volume, and mix.

Assay preparation— Remove, as completely as possible, the contents of not less than 20 Capsules. Transfer an accurately weighed portion of the powder, equivalent to about 100 mg of secobarbital sodium, to a separator, add 20 mL of water, 1 mL of hydrochloric acid, and 100.0 mL of chloroform, and shake for 3 minutes. Remove the chloroform layer, and use as directed in the Procedure.

Chromatographic system (see Chromatography 621)—The gas chromatograph is equipped with a flame-ionization detector and contains a 0.6-m × 3.5-mm glass column packed with 3 percent liquid phase G10 on 100- to 120-mesh support S1AB. The column is maintained at about 175, the injection port at about 235, the detector block at about 245, and dry helium is used as the carrier gas at a flow rate of about 55 mL per minute. Chromatograph five replicate injections of the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation is not more than 2%; the resolution factor between amobarbital and the internal standard is not less than 1.5; the resolution factor between amobarbital and secobarbital is not less than 2.5; and the tailing factor does not exceed 1.5 for any of the three peaks.

Procedure— Mix 5.0 mL of the Standard preparation with 5.0 mL of the Internal standard solution. Mix 5.0 mL of the Assay preparation with 5.0 mL of the Internal standard solution. Separately inject equal volumes (about 3 µL) of the resulting solutions into the chromatograph, and record the chromatograms. Measure the responses for the major peaks. The relative retention times with respect to the internal standard are about 1.3 for amobarbital and 1.8 for secobarbital. Calculate the quantity, in mg, of secobarbital sodium (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, W is the weight, in mg, of USP Secobarbital RS taken for the Standard preparation, and RU and RS are the ratios of the peak response of secobarbital to that of the internal standard in the Assay preparation and the Standard preparation, respectively. Similarly calculate the quantity, in mg, of amobarbital sodium (C11H17N2NaO3) in the portion of Capsules taken by the formula: in which 248.26 and 226.28 are the molecular weights of amobarbital sodium and amobarbital, respectively, W ¢ is the weight, in mg, of USP Amobarbital RS taken for the Standard preparation, and R¢U and R¢S are the ratios of the peak response of amobarbital to that of the internal standard obtained from Assay preparation and the Standard preparation, respectively.