A: Infrared Absorption 197K.

B: Ultraviolet Absorption 197U—

Solution: 6 µg per mL.

Medium: methanol.

Test solution: 10 mg per mL, in trichloroethane.

Mobile phase , System suitability preparation, and Chromatographic system—Prepare as directed in the Assay.

Test solution— Prepare a solution of Dydrogesterone in Mobile phase having a concentration of about 0.1 mg per mL.

Procedure— Inject about 20 µL of the Test solution into the chromatograph, record the chromatograms for not less than 20 minutes, and measure the peak area responses. The sum of the areas of the secondary peaks, is not more than 2.0% of the total peak area.

Mobile phase— Prepare a filtered and degassed mixture of water, alcohol, and acetonitrile (530:260:210). Make adjustments if necessary (see System Suitability under Chromatography 621).

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

Assay preparation— Transfer about 100 mg of Dydrogesterone, accurately weighed, to a 100-mL volumetric flask, add Mobile phase to volume, and mix. Transfer 10.0 mL of the resulting solution to a 100-mL volumetric flask, dilute with Mobile phase to volume, and mix.

System suitability preparation— Transfer 10 mg of dydrogesterone to a 100-mL volumetric flask, add 30 mL of alcohol, and mix to dissolve the solid. Add 1 mL of 0.2 N sodium hydroxide, and heat the mixture at 85 for 10 minutes. Cool to room temperature, neutralize with 1 mL of 0.2 N hydrochloric acid, add 20 mL of acetonitrile, dilute with water to volume, and mix. This solution contains dydrogesterone and 17 -dydrogesterone.

Chromatographic system— The liquid chromatograph is equipped with a 280-nm detector and a 4.6-mm × 15-cm column that contains 3-µm packing L1 and is maintained at 40. The flow rate is about 1 mL per minute. Chromatograph 20 µL of the System suitability preparation, and record the peak responses as directed under Procedure: the resolution between the dydrogesterone and 17 -dydrogesterone is not less than 5, and the relative standard deviation of dydrogesterone peak responses from replicate injections is not more than 1.5%. The relative retention times are about 1.0 for dydrogesterone and about 1.3 for 17 -dydrogesterone.

Procedure— Separately inject equal volumes (about 20 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 quantity, in mg, of C21H28O2 in the portion of Dydrogesterone taken by the formula: in which C is the concentration, in mg per mL, of USP Dydrogesterone RS in the Standard preparation, and rU and rS are the peak responses for dydrogesterone obtained from the Assay preparation and the Standard preparation, respectively.