A:Infrared Absorption á197Kñ.

B:Ultraviolet Absorption á197Uñ—

Solution: 10µg per mL.

Medium: methanol.

Test solution: 20mg per mL,in dioxane.

Mobile phase— Prepare a filtered and degassed mixture of water and isopropyl alcohol (72:28).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Internal standard solution— Transfer about 66mg of methyltestosterone to a 10-mLvolumetric flask,add dilute alcohol (85in 100)to volume,and mix.

Standard preparation— Dissolve an accurately weighed quantity of USP Progesterone RSin dilute alcohol (85in 100)to obtain a solution having a known concentration of about 2.5mg per mL.Transfer 4.0mLof this solution to a 10-mLvolumetric flask,add 1.0mLof Internal standard solution,then add dilute alcohol (85in 100)to volume,and mix to obtain a solution having a known concentration of about 1mg of USP Progesterone RSper mL.

Assay preparation— Transfer about 10mg of Progesterone,accurately weighed,to a 10-mLvolumetric flask,add 1.0mLof Internal standard solution,then add dilute alcohol (85in 100)to volume,and mix.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 254-nm detector and a 4-mm ×30-cm column that contains 10-µm packing L1.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the resolution,R,between the analyte and internal standard peaks is not less than 3.5;and the relative standard deviation for replicate injections is not more than 1.5%.

Procedure— Separately inject equal volumes (5µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.The relative retention times are about 2.0for progesterone and 1.0for methyltestosterone.Calculate the quantity,in mg,of C21H30O2in the portion of Progesterone taken by the formula: in which Cis the concentration,in mg per mL,of USP Progesterone RSin the Standard preparation;and RUand RSare the peak response ratios obtained from the Assay preparationand the Standard preparation,respectively.