Pentobarbital
;)
2,4,6(1H,3H,5H)-Pyrimidinetrione,5-ethyl-5-(1-methylbutyl)-,(±)-.
(±)-5-Ethyl-5-(1-methylbutyl)barbituric acid [76-74-4].
Change to read:
»Pentobarbital contains not less than 
98.0USP28percent and not more than 102.0USP28percent of C11H18N2O3,calculated on the dried basis.
98.0USP28percent and not more than 102.0USP28percent of C11H18N2O3,calculated on the dried basis.
Packaging and storage—
Preserve in tight containers.
Change to read:
Identification—
A:Infrared Absorption á197Sñ—
Solution:
7in 100.
Medium:
chloroform.
C:
The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.USP28
The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.USP28
Loss on drying á731ñ—
Dry it at 105
for 2hours:it loses not more than 1.0%of its weight.
for 2hours:it loses not more than 1.0%of its weight.
Residue on ignition á281ñ:
not more than 0.1%.
Heavy metals,Method IIá231ñ:
0.002%.
Organic volatile impurities,Method Vá467ñ:
meets the requirements.
Solvent—
Use dimethyl sulfoxide.
Add the following:
Related compounds—
Mobile phase—
Prepare as directed in the Assay.
Standard solution—
Dissolve an accurately weighed quantity of USP Pentobarbital RSin Mobile phase,and dilute quantitatively,and stepwise if necessary,with Mobile phaseto obtain a solution having a known concentration of about 0.001mg per mL.
Test solution—
Transfer about 100mg of Pentobarbital,accurately weighed,to a 100-mLvolumetric flask,add about 80mLof Mobile phase,and sonicate until dissolved.Dilute with Mobile phaseto volume,and mix.
Chromatographic system (see Chromatography á621ñ)—
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 1.0mLper 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 15,000theoretical 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 10µL)of the Standard solutionand Test solutioninto the chromatograph,record the chromatograms,and measure the areas for the major peaks.Calculate the percentage of any impurity in the portion of Pentobarbital taken by the formula:
USP28
(10,000/F)(C/W)(ri/rS),
in which Cis the concentration,in mg per mL,of USP Pentobarbital RSin the Standard solution;Fis the relative response factor of the impurity according the table below;Wis the weight,in mg,of pentobarbital,on dried basis,used to prepare the Test solution;riis the peak area for any impurity in the Test solution;and rSis 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-ethylpropyl) 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%.
|
|||
USP28
Delete the following:
Isomer content—
Transfer 300±5mg to a round-bottom flask equipped with a standard-taper,ground-glass joint,and add 4mLof water.Add,dropwise,sodium hydroxide solution (4in 10)just to dissolve the specimen (about 3or 4drops),then add 10mLof alcohol.Add 300±5mg of p-nitrobenzyl bromide,mix,attach a condenser,and reflux for 30minutes.Cool,filter under reduced pressure,and wash the residue with four 5-mLportions of water.Transfer the residue,as completely as possible,to a small flask,add 25mLof alcohol,and reflux for 10minutes:the solid dissolves completely.Cool,and filter under reduced pressure:the p-nitrobenzyl derivative so obtained,after being dried at 105for 30minutes,melts completely between 136and 146,when determined by the procedure for Class Ia(see Melting Range or Temperature á741ñ).USP28
Change to read:
Assay—
Mobile phase—
Prepare a filtered and degassed pH3.5mixture of 0.01Mmonobasic potassium phosphate and acetonitrile (65:35).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).
Standard preparation—
Dissolve an accurately weighed quantity of USP Pentobarbital RSin Mobile phase,and dilute quantitatively,and stepwise if necessary,with Mobile phaseto obtain a solution having a known concentration of about 0.1mg per mL.
Assay preparation—
Transfer about 100mg of Pentobarbital,accurately weighed,to a 100-mLvolumetric flask,add about 80mLof Mobile phase,and sonicate until dissolved.Dilute with Mobile phaseto volume,and mix.Transfer 10.0mLof this solution to a 100-mLvolumetric flask.Dilute with Mobile phaseto volume,and mix.
Chromatographic system (see Chromatography á621ñ)—
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 1.0mLper minute.Chromatograph the Standard preparation,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 15,000theoretical plates;the tailing factor is not more than 1.5;and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure—
Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the peak responses for the major peak.Calculate the quantity,in mg,of C11H18N2O3in the portion of Pentobarbital taken by the formula:
USP28
1000C(rU/rS),
in which Cis the concentration,in mg per mL,of USP Pentobarbital RSin the Standard preparation;and rUand rSare the peak areas obtained from the Assay preparationand the Standard preparation,respectively.USP28
Auxiliary Information—
Staff Liaison:Ravi Ravichandran,Ph.D.,Senior Scientist
Expert Committee:(PA3)Pharmaceutical Analysis 3
USP28–NF23Page 1507
Pharmacopeial Forum:Volume No.30(1)Page 154
Phone Number:1-301-816-8330