Pentobarbital Elixir
(Current title—not to change until June 1,2005)
Monograph title change—to become official June 1,2005
See Pentobarbital Oral Solution
»Pentobarbital Elixir contains not less than 92.5percent and not more than 107.5percent of the labeled amount of C11H18N2O3.
Packaging and storage— Preserve in tight containers.
Identification— Dilute a volume of Elixir with alcohol to a concentration of about 1mg of pentobarbital per mL.Apply 50µLof this solution and 50µLof a Standard solution of USP Pentobarbital RSin alcohol containing 1mg per mLas streaks about 1cm in length along the spotting line to a suitable thin layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture.Allow the streaks to dry,and develop the chromatogram in a solvent system consisting of a mixture of isopropyl alcohol,ammonium hydroxide,chloroform,and acetone (9:4:2:2)until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,mark the solvent front,and allow the solvent to evaporate.Locate the spots by viewing the plate under short-wavelength UVlight:the RFvalue of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.
Alcohol content,Method Iá611ñ: between 16.0%and 20.0%of C2H5OH.
Assay—
Internal standard— n-Tricosane.
Internal standard solution— Dissolve an accurately weighed quantity of n-tricosane in chloroform,and quantitatively dilute with chloroform to obtain a solution having a known concentration of about 0.6mg per mL.
Standard preparation— Dissolve accurately weighed quantities of USP Pentobarbital RSand n-tricosane in chloroform,and quantitatively dilute with chloroform to obtain a solution that contains,in each mL,known amounts of about 1mg of USP Pentobarbital RSand about 0.4mg of n-tricosane.
Assay preparation— Transfer an accurately measured volume of Elixir,equivalent to about 20mg of pentobarbital,to a separator,add 1mLof dilute hydrochloric acid (1in 5),and extract with four 10-mLportions of chloroform.Filter the extracts through about 15g of anhydrous sodium sulfate that is supported on a funnel by a small pledget of glass wool.Collect the combined filtrate in a 50-mLvolumetric flask,wash the sodium sulfate with 5mLof chloroform,dilute with chloroform to volume,and mix.Combine 4.0mLof this solution with 1.0mLof Internal standard solutionin a suitable container,and reduce the volume to about 1.5mLby evaporation,with the aid of a stream of dry nitrogen,at room temperature.
Chromatographic system andSystem suitability— Proceed as directed for Chromatographic Systemand System Suitabilityunder Barbiturate Assay á361ñ,the resolution,R,between pentobarbital and n-tricosane being not less than 2.3.[NOTE—Relative retention times are,approximately,0.5for n-tricosane and 1.0for pentobarbital.]
Procedure— Proceed as directed for Procedureunder Barbiturate Assay á361ñ.Calculate the quantity,in mg,of C11H18N2O3in each mLof the Elixir taken by the formula:
12.5(RU)(QS)(Ci)/V(RS),
in which Vis the volume,in mL,of Elixir taken;and the other terms are as defined therein.
Auxiliary Information— Staff Liaison:Ravi Ravichandran,Ph.D.,Senior Scientist
Expert Committee:(PA3)Pharmaceutical Analysis 3
USP28–NF23Page 1509
Pharmacopeial Forum:Volume No.28(2)Page 342
Phone Number:1-301-816-8330