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

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

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

Chromatographic system (see Chromatography 621)— Proceed as directed under Assay Test 1, except to chromatograph the Standard solution six times and chromatograph the Resolution solution: the relative retention time is about 0.18 for 2,6-diisopropylphenyl-isopropyl ether, 1.0 for propofol, and about 1.1 for 2-isopropyl-6-n-propylphenol; the resolution, R, between propofol and 2-isopropyl-6-n-propylphenol is not less than 2. Chromatograph the Standard solution six times, and record the peak responses as directed for Procedure: the column efficiency determined from the propofol peak is not less than 5000 theoretical plates; and the relative standard deviation for replicate injections is not more than 3.5%.

Procedure— Separately inject equal volumes (about 1.0 µL) of the Resolution solution, the Standard solution, and the Test 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 ri is the peak response for each impurity obtained from the Test solution; and rS is the peak response for propofol obtained from the Standard solution: not more than 0.1% of 2,6-diisopropylphenyl-isopropyl ether 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 5 µL of USP Propofol RS and 15 µL of USP Propofol Related Compound B RS to a 50-mL volumetric flask, dissolve in and dilute with hexane to volume, and mix.

System suitability solution 2— Dissolve an accurately weighed quantity of USP Propofol Related Compound A RS and accurate volumes of the propofol that is under test and USP Propofol Related Compound C RS in hexane, and dilute quantitatively, and stepwise if necessary, with hexane to obtain a solution having known concentrations of 0.25 mg of propofol related compound A per mL, 100 µL of propofol per mL, and 5 µL of propofol related compound C per mL.

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

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

Chromatographic system (see Chromatography 621)— Proceed as directed in Assay Test 2. Chromatograph System suitability solution 1 and System suitability solution 2, and record the peak responses as directed for Procedure: the relative retention times are about 0.8 for propofol related compound B from System suitability solution 1, 0.5 for 2,6-diisopropylphenylisopropyl ether, 1.0 for propofol, and 5.0 for propofol related compound A from System suitability solution 2; and the resolution, R, between propofol related compound B and propofol is at least 4.0.

Procedure— Separately inject a volume (about 10 µL) of the Test solution and the Reference solution into 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 ri is the peak response for each impurity obtained from the Test solution; rS is the peak response for propofol obtained from the Reference solution; and F is the response factor. F is 0.2 for 2,6-diisopropylphenylisopropyl ether and 4.0 for propofol related compound A: not more than 0.2% of 2,6-diisopropylphenylisopropyl ether is found; not more than 0.01% of propofol related compound A is found; not more than 0.05% of each of the other individual impurities 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 330 nm using air as the blank (see Ultraviolet Absorption 197U. The absorbance of the Sample solution is not more than 0.4 absorbance units (0.1%).

Mobile phase— Prepare as directed under Assay Test 2.

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

Standard solution— Dilute 5 mL of the Standard stock solution with hexane to 100 mL.

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

Chromatographic system (see Chromatography 621)— Prepare as directed under Assay Test 2 except that the liquid chromatograph is equipped with a detector at 254 nm. Chromatograph the Standard solution and the Test solution, and record the peak responses as directed for Procedure: the relative retention time for propofol related compound B is about 0.8 and 1.0 for propofol.

Procedure— Separately inject equal volumes (about 20 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the peak responses. Calculate the percentage of propofol related compound B in the portion of Propofol taken by the formula: in which CS is the concentration, in mg per mL, of the Standard solution; CU is the concentration, in mg per mL, of propofol in the Test solution; and rU and rS are the peak responses obtained from the Test solution and the Standard solution, respectively: not more than 0.05% of propofol related compound B is found.

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

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

Chromatographic system (see Chromatography 621)— 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 8 mL per minute. The injection port and the detector temperatures are maintained at 250 and 300, respectively. The chromatograph is programmed as follows. Upon injection, the column temperature is maintained at 145 for 20 minutes; the temperature is increased at a rate of 5 per minute to 200 and maintained at 200 for 5 minutes. Chromatograph the Standard preparation five times, and record the peak responses as directed for Procedure: the column efficiency determined from the propofol peak is not less than 5000 theoretical 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 1.0 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 percentage of C12H18O in the portion of Propofol taken by the formula: in which CS is the concentration, in mg per mL, of USP Propofol RS in the Standard preparation; CU is the concentration, in mg per mL, of Propofol in the Assay preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.

Mobile phase— Prepare a filtered and degassed mixture of hexane, acetonitrile, and alcohol (990:7.5:1). Make adjustments if necessary (see System Suitability under Chromatography 621).

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

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

Chromatographic system (see Chromatography 621)— 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 2 mL per 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 10 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the propofol peaks. Calculate the quantity, in mg, of C12 H18O in the portion of Propofol taken by formula: in which CS is the concentration, in mg per mL, of USP Propofol RS in the Standard preparation; CU is the concentration, in mg per mL, of Propofol in the Assay preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.