A: Infrared Absorption 197K—

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.

Test solution: 10 mg per mL, in chloroform.

Internal standard solution— Prepare a solution of isobutyl alcohol in dimethylformamide containing 2 µL of isobutyl alcohol per 100 mL of solution.

Standard solution— Prepare a solution in Internal standard solution containing 5 µL each of acetone, alcohol, chloroform, diisopropyl ether, and methanol per 100 mL of solution.

System suitability solution— Dilute a portion of the Standard solution with Internal standard solution to obtain a solution containing 0.05 µL each of acetone, alcohol, chloroform, diisopropyl ether, and methanol per 100 mL of solution.

Test solution— Transfer about 40 mg of Norgestimate and 2 mL of Internal standard solution to a 5-mL volumetric flask or a suitable vial, and shake well to dissolve.

Chromatographic system (see Chromatography 621)— The gas chromatograph is equipped with a flame-ionization detector, a 0.53-mm × 30-m fused-silica capillary column bonded with a 1-µm layer of phase G16, and a split injection system. The detector temperature is maintained at about 250, and the injection port temperature is maintained at about 180. The chromatograph is programmed as follows. The column temperature is maintained at about 65 for 2.5 minutes, then the temperature is increased at a rate of 35 per minute to 100, maintained at 100 for 2 minutes, then increased at a rate of 30 per minute to 160, and maintained at 160 for 2.5 minutes. The carrier gas is helium, flowing at a rate of about 6 mL per minute, and the split flow rate is about 16 mL per minute. Chromatograph the Internal standard solution, the Standard solution, and the System suitability solution, and record the peak responses as directed for Procedure: there are no interfering peaks due to dimethylformamide; the retention time of isobutyl alcohol in the chromatogram of the Internal standard solution is between 4 and 5 minutes; the signal-to-noise ratio for alcohol obtained from the System suitability solution is not less than 2.0; and the relative standard deviation for replicate injections of the Standard solution, determined from the peak response ratios of each solvent to the internal standard, is not more than 3.0%.

Procedure— Separately inject equal volumes (about 1 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the percentage of each solvent in the portion of Norgestimate taken by the formula: in which C is the concentration, in mL per mL, of each solvent in the Standard solution; D is the density, in mg per mL, of each solvent; W is the weight, in mg, of Norgestimate taken to prepare the Test solution; and RU and RS are the peak response ratios of the appropriate analyte to the internal standard obtained from the Test solution and the Standard solution, respectively. Option 1: not more than 0.5% each of acetone and alcohol is found, not more than 0.05% of diisopropyl ether is found, not more than 0.006% of chloroform is found, and not more than 0.3% of methanol is found; or Option 2: meets the requirements.

test 1—

test 2—

Diluent— Prepare a mixture of methanol and water (4:1).

Mobile phase— Prepare a filtered and degassed mixture of water, tetrahydrofuran, and acetonitrile (30:11:9). Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Norgestimate RS in Diluent, and dilute quantitatively, and stepwise if necessary, with Diluent to obtain a solution having a known concentration of about 0.5 mg per mL.

Sensitivity solution— Dilute a portion of Standard preparation, quantitatively and stepwise if necessary, with Diluent to obtain a solution having a known concentration of about 0.05 µg per mL.

Assay preparation— Transfer about 25 mg of Norgestimate, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with Diluent to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 244-nm detector and a 4.6-mm × 10-cm column that contains 3-µm packing L1. The flow rate is about 1.2 mL per minute. The column temperature is maintained at about 40. Chromatograph the Sensitivity solution,and record the peak areas as directed for Procedure: the signal-to-noise ratio for (Z)-norgestimate is not less than 3.0. Chromatograph the Standard preparation, and record the peak areas as directed for Procedure: the relative retention times are about 0.86 for (Z)-norgestimate and 1.0 for (E)-norgestimate; the resolution, R, between (Z)-norgestimate and (E)-norgestimate is not less than 1.5; the tailing factor for (E)-norgestimate and for (Z)-norgestimate is not more than 1.5; and the relative standard deviation for replicate injections, determined from the peak area ratio of (E)-norgestimate to (Z)-norgestimate, is not more than 2.0%.

Procedure— Separately inject equal volumes (about 25 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the areas for the major peaks. Calculate the quantity, in mg, of C23H31NO3 in the portion of Norgestimate taken by the formula: in which C is the concentration, in mg per mL, of USP Norgestimate RS in the Standard preparation; and rU and rS are the sums of the peak areas of (Z)-norgestimate and (E)-norgestimate obtained from the Assay preparation and the Standard preparation, respectively. Calculate the percentages of the (Z)- and (E)-isomers, UZ and UE, respectively, in the portion of Norgestimate taken by the formula: in which C is the concentration, in mg per mL, of USP Norgestimate RS in the Standard preparation; P is the fraction of (E)- or (Z)-norgestimate in USP Norgestimate RS; W is the weight, in mg, of Norgestimate taken to prepare the Assay preparation; and rU and rS are the peak responses of the appropriate norgestimate isomer obtained from the Assay preparation and the Standard preparation, respectively. Calculate the ratio of (E)-norgestimate to (Z)-norgestimate, that is, the ratio of UE to UZ.