Identification—
A: Ultraviolet Absorption 
197U
—
Solution:
10 µg per mL.
Medium:
dilute ammonium hydroxide (1 in 200).
B:
The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.
C:
Ignite about 200 mg: the residue effervesces with acids, and meets the requirements of the tests for
Sodium 191.
Related compounds—
Mobile phase—
Prepare as directed in the Assay.
Standard solution—
Dissolve an accurately weighed quantity of
USP Pentobarbital RS in
Mobile phase, and dilute quantitatively, and stepwise if necessary, with
Mobile phase to obtain a solution having a known concentration of about 0.001 mg per mL.
Test solution—
Transfer about 110 mg of Pentobarbital Sodium, accurately weighed, to a 100-mL volumetric flask, add about 80 mL of Mobile phase, and sonicate until dissolved. Dilute with Mobile phase to volume, and mix.
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 214-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L1. The flow rate is about 1.0 mL per minute. Chromatograph the
Standard solution, and record the peak responses as directed for
Procedure: the capacity factor,
k¢, is not less than 2.5; the column efficiency is not less than 15,000 theoretical plates; the tailing factor is not more than 1.5; and the relative standard deviation for replicate injections is not more than 15.0%.
Procedure—
Separately inject equal volumes (about 10 µL) of the
Standard solution and
Test solution into the chromatograph, record the chromatograms, and measure the areas for the major peaks. Calculate the percentage of any impurity in the portion of Pentobarbital Sodium taken by the formula:
(248.25/226.27)(10,000/F)(C/W)(ri / rS)
in which 248.25 and 226.27 are the molecular weights of pentobarbital sodium and pentobarbital, respectively;
F is the relative response factor of the impurity according to the table below;
C is the concentration, in mg per mL, of
USP Pentobarbital RS in the
Standard solution; W is the weight, in mg, of Pentobarbital Sodium, on the dried basis, used to prepare the
Test solution; ri is the peak area for any impurity in the
Test solution; and
rS is the peak area for pentobarbital in the
Standard solution: the impurities meet the requirements given in the table below:
Compound
Name |
Relative
Retention
Time |
Relative
Response
Factor |
Limit (%) |
6-Imino-5-ethyl-
5-(1-methyl-
butyl)barbituric
acid |
about 0.39 |
1.5 |
0.2 |
5-Ethyl-5-(1-ethyl-
propyl)barbituric
acid* |
about 0.93 |
1.0 |
0.1 |
| Pentobarbital |
1.0 |
— |
— |
5-Ethyl-5-(1,3-
dimethylbutyl)
barbituric acid |
about 1.5 |
0.9 |
0.3 |
Unknown
impurities |
— |
1.0 |
0.1 |
| Total |
— |
— |
0.5 |
|
*
Where the material is labeled as intended solely for veterinary use, the limit of 5-ethyl-5-(1-ethylpropyl) barbituric acid is 3.0%.
|
Assay—
[NOTE—Use the value for
Loss on drying obtained at the same time as the preparation of the
Test solution in the test for
Related compounds and the
Assay preparation in the
Assay.]
Mobile phase, Standard preparation, and Chromatographic system—
Proceed as described in the Assay under Pentobarbital.
Assay preparation—
Transfer about 110 mg of Pentobarbital Sodium, accurately weighed, to a 100-mL volumetric flask, add about 80 mL of Mobile phase, and sonicate until dissolved. Dilute with Mobile phase to volume, and mix. Transfer 10.0 mL of this solution to a 100-mL volumetric flask. Dilute with Mobile phase to volume, and mix.
Procedure—
Separately inject equal volumes (about 10 µL) of the
Standard preparation and the
Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C
11H
17N
2NaO
3 in the portion of Pentobarbital Sodium taken by the formula:
(248.25/226.27)1000C(rU / rS)
in which 248.25 and 226.27 are the molecular weights of pentobarbital sodium and pentobarbital, respectively;
C is the concentration, in mg per mL, of
USP Pentobarbital RS in the
Standard preparation; and
rU and
rS are the peak areas obtained from the
Assay preparation and the
Standard preparation, respectively.
Where the material is labeled as intended solely for veterinary use, Pentobarbital Sodium contains not less than 97.0 percent and not more than 102.0 percent of C11H17N2NaO3, calculated on the dried basis.
for 6 hours: it loses not more than 3.5% of its weight.