Test solution :10mg per mL,in chloroform.

Mobile phase— Prepare a filtered and degassed mixture of water,tetrahydrofuran,and methanol (60:25:15).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Internal standard solution— Prepare a solution of progesterone in methanol containing 0.6mg per mL.

Standard preparation— Prepare a solution of USP Mibolerone RSin Internal standard solutionhaving a known concentration of about 0.4mg per mL.Mix,and sonicate if necessary to achieve complete solution.

Assay preparation— Transfer about 10mg of Mibolerone,accurately weighed,to a 25-mLvolumetric flask,dilute with Internal standard solutionto volume,and mix.Sonicate if necessary to achieve complete solution.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The flow rate is about 2mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative retention times are about 0.6for mibolerone and 1.0for progesterone;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 5µL)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 C20H30O2in the portion of Mibolerone taken by the formula: in which Cis the concentration,in mg per mL,of USP Mibolerone RSin the Standard preparation;and RUand RSare the ratios of the peak responses of the mibolerone peak and the progesterone peak obtained from the Assay preparationand the Standard preparation,respectively.