A: Infrared Absorption á197Kñ.

B: Ultraviolet Absorption á197Uñ—

Solution: 6µg per mL.

Medium: methanol.

Test solution: 10mg 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 phasehaving a concentration of about 0.1mg per mL.

Procedure— Inject about 20µLof the Test solutioninto the chromatograph,record the chromatograms for not less than 20minutes,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 Suitabilityunder Chromatography á621ñ).

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

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

System suitability preparation— Transfer 10mg of dydrogesterone to a 100-mLvolumetric flask,add 30mLof alcohol,and mix to dissolve the solid.Add 1mLof 0.2Nsodium hydroxide,and heat the mixture at 85for 10minutes.Cool to room temperature,neutralize with 1mLof 0.2Nhydrochloric acid,add 20mLof acetonitrile,dilute with water to volume,and mix.This solution contains dydrogesterone and 17a-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 L1and is maintained at 40.The flow rate is about 1mLper minute.Chromatograph 20µLof the System suitability preparation,and record the peak responses as directed under Procedure:the resolution between the dydrogesterone and 17a-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 1.0for dydrogesterone and about 1.3for 17a-dydrogesterone.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C21H28O2in the portion of Dydrogesterone taken by the formula: in which Cis the concentration,in mg per mL,of USP Dydrogesterone RSin the Standard preparation,and rUand rSare the peak responses for dydrogesterone obtained from the Assay preparationand the Standard preparation,respectively.