Resolution solution— Dissolve an accurately weighed quantity of USP Propofol Resolution RSin methanol,and dilute quantitatively,and stepwise if necessary,with methanol to obtain a solution having a concentration of about 100mg per mL.

Standard solution— Dissolve an accurately weighed quantity of USP Propofol RSin methanol,and dilute quantitatively,and stepwise if necessary,with methanol to obtain a solution having a concentration of about 0.1mg per mL.

Test solution— Transfer about 1000mg of Propofol,accurately weighed,to a 10-mLvolumetric flask,dissolve in and dilute with methanol to volume,and mix.

Chromatographic system(see Chromatography á621ñ)— Proceed as directed under Assay Test 1,except to chromatograph the Standard solutionsix times and chromatograph the Resolution solution:the relative retention time is about 0.18for 2,6-diisopropylphenyl isopropylether,1.0for propofol,and about 1.1for 2-isopropyl-6-n-propylphenol;the resolution,R,between propofol and 2-isopropyl-6-n-propylphenol is not less than 2.Chromatograph theStandard solution six times,and record the peak responses as directed forProcedure:the column efficiency determined from the propofol peak is not less than 5000theoretical plates;and the relative standard deviation for replicate injections is not more than 3.5%.

Procedure— Separately inject equal volumes (about 1.0µL)of theResolution solution,the Standard solution,and theTest solution into the chromatograph,record the chromatograms,and measure all the peak responses.Calculate the percentage of each impurity in the portion of Propofol taken by the formula: in which riis the peak response for each impurity obtained from theTest solution;and rSis the peak response for propofol obtained from theStandard solution:not more than 0.1%of 2,6-diisopropylphenyl isopropylether is found;not more than 0.1%of each other individual impurity is found;and not more than 0.3%of total impurities is found.

Mobile phase— Prepare as directed in Assay Test 2.

System suitability solution 1— Transfer 5µLof USP Propofol RSand 15µLof USP Propofol Related Compound B RSto a 50-mLvolumetric flask,dissolve in and dilute with hexane to volume,and mix.

System suitability solution 2— Dissolve 1mLof USP Propofol for System Suitability RSwith hexane to make 10mL.

Test solution— Transfer about 1000mg of Propofol,accurately weighed,to a 10-mLvolumetric flask,dissolve in and dilute with hexane to volume,and mix.

Reference solution— Dilute 1mLof the Test solution with hexane to 100mL,and mix.Dilute 1mLof this solution with hexane to 10mL,and mix.

Chromatographic system (see Chromatography á621ñ)— Proceed as directed in Assay Test 2.Chromatograph System suitability solution 1andSystem suitability solution 2,and record the peak responses as directed for Procedure:the relative retention times are about 0.8for propofol related compound Bfrom System suitability solution 1,0.5for 2-(1-methylethoxy)-1,3-bis(1-methylethylbenzene),1.0for propofol,and 5.0for propofol related compound Afrom System suitability solution 2;the resolution,R,between propofol related compound Band propofol is at least 4.0.

Procedure— Separately inject a volume (about 10µL)of the Test solutionand theReference solutioninto the chromatograph,record the chromatogram,and measure all peak responses.Calculate the percentage of each impurity in the portion of Propofol taken by the formula: in which riis the peak response for each impurity obtained from the Test solution;rSis the peak response for propofol obtained from the Reference solution;and Fis the response factor.Fis 0.2for 2,6-diisopropylphenylisopropyl ether and 4.0for propofol related compound A:not more than 0.2%of 2-(1-methylethoxy)-1,3-bis(1-methylethylbenzene)is found;not more than 0.2%of 2,6-diisopropylphenylisopropyl ether is found;not more than 0.01%of propofol related compound Ais found;not more than 0.05%of each other individual impurity is found;and not more than 0.3%of total impurities is found.

0.01(rU/rS),

Sample solution: neat.

Procedure— Examine the portion of Propofol taken at 330nm using air as the blank (seeUltraviolet Absorption á197Uñ.The absorbance of theSample solution is not more than 0.4absorbance units (0.1%).

Mobile phase— Prepare as directed under Assay Test 2.

Standard stock solution— Dissolve about 5mg of USP Propofol Related Compound B RSin hexane,and dilute with hexane to 50mL.

Standard solution— Dilute 5mLof the Standard stock solutionwith hexane to 100mL.

Test solution— Dissolve about 0.5g of Propofol in hexane,and dilute with hexane to 10mL.

Chromatographic system (see Chromatography á621ñ)— Prepare as directed under Assay Test 2except that the liquid chromatograph is equipped with a detector at 254nm.Chromatograph the Standard solutionand the Test solution,and record the peak responses as directed for Procedure:the relative retention time for propofol related compound Bis about 0.8and 1.0for propofol.

Procedure— Separately inject equal volumes (about 20µL)of the Standard solutionand the Test solution into the chromatograph,record the chromatograms,and measure the peak responses.Calculate the percentage of propofol related compound Bin the portion of Propofol taken by the formula: in which CSis the concentration,in mg per mL,of the Standard solution;CUis the concentration,in mg per mL,of propofol in the Test solution;and rUand rSare the peak responses obtained from the Test solutionand the Standard solution,respectively:not more than 0.05%of propofol related compound Bis found.

Standard preparation— Dissolve an accurately weighed quantity of USP Propofol Resolution RSin methanol,and dilute quantitatively,and stepwise if necessary,with methanol to obtain a solution having a concentration of about 10mg per mL.

Assay preparation— Transfer about 250mg of Propofol,accurately weighed,to a 25-mLvolumetric flask,and dissolve in and dilute with methanol to volume.

Chromatographic system (see Chromatography á621ñ)— The gas chromatograph is equipped with a flame-ionization detector and a 0.53-mm ×30-m column coated with a 1.2-µm phase G16.The carrier gas is helium,flowing at a rate of about 8mLper minute.The injection port and the detector temperatures are maintained at 250and 300,respectively.The chromatograph is programmed as follows.Upon injection,the column temperature is maintained at 145for 20minutes;the temperature is increased at a rate of 5per minute to 200and maintained at 200for 5minutes.Chromatograph the Standard preparationfive times,and record the peak responses as directed for Procedure:the column efficiency determined from the propofol peak is not less than 5000theoretical plates;the tailing factor is not more than 2.5;and the relative standard deviation for replicate injections is not more than 1.5%.

Procedure— Separately inject equal volumes (about 1.0µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the peak responses for the major peaks.Calculate the percentage of C12H18Oin the portion of Propofol taken by the formula: in which CSis the concentration,in mg per mL,of USP Propofol RSin the Standard preparation;CUis the concentration,in mg per mL,of propofol in the Assay preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.

Mobile phase— Prepare a filtered and degassed mixture of hexane,acetonitrile,and ethanol (990:7.5:1).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Propofol RSin hexane,and dilute quantitatively,and stepwise if necessary,with hexane to obtain a solution having a concentration of about 2.4mg per mL.

Assay preparation— Transfer about 240mg of Propofol,accurately weighed,to a 100-mLvolumetric flask,dissolve in and dilute with hexane to volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 275-nm detector and 4.6-mm ×20-cm column that contains 5-µm packing L3.The flow rate is about 2mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure: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 responses for the propofol peaks.Calculate the quantity,in mg,of C12H18Oin the portion of Propofol taken by formula: in which CSis the concentration,in mg per mL,of USP Propofol RSin the Standard preparation;CUis the concentration,in mg per mL,of propofol in the Assay preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.