Test solution: 20mg per mL,in chloroform.

Mobile phase— Prepare a solution of acetonitrile and water (55:45),mix,and degas.The acetonitrile concentration may be varied slightly to meet system suitability test requirements and to provide a suitable elution time.

Solvent mixture— Mix 60volumes of water and 40volumes of acetonitrile.

Internal standard solution— Transfer about 80mg of propylparaben to a 100-mLvolumetric flask,dissolve in acetonitrile,add acetonitrile to volume,and mix.

Standard preparation— Using an accurately weighed quantity of USP Megestrol Acetate RS,prepare a solution in acetonitrile containing about 1mg per mL.Transfer 4.0mLof this solution and 5.0mLof Internal standard solutionto a 50-mLvolumetric flask,dilute with Solvent mixtureto volume,and mix.The Standard preparationhas a known concentration of about 80µg of megestrol acetate per mL.

Assay preparation— Transfer about 100mg of Megestrol Acetate,accurately weighed,to a 100-mLvolumetric flask.Dissolve in acetonitrile,add acetonitrile to volume,and mix.Transfer 4.0mLof this solution and 5.0mLof Internal standard solutionto a 50-mLvolumetric flask,dilute with Solvent mixtureto volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with an UVdetector that monitors absorption at 280nm and 3.9-mm ×30-cm column containing packing L1.The flow rate is about 1mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative retention times are about 0.4for propylparaben and 1.0for megestrol acetate;the resolution factor,R(see Chromatography á621ñ),between the peaks for propylparaben and megestrol acetate is not less than 8.0;and the relative standard deviation of the peak response ratio,RS,for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 25µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the peak responses of the major peaks.Calculate the quantity,in mg,of C24H32O4in the portion of Megestrol Acetate taken by the formula: in which Cis the concentration,in µg per mL,of USP Megestrol Acetate RSin the Standard preparation;and RUand RSare the ratios of the peak responses of megestrol acetate and propylparaben obtained from the Assay preparationand the Standard preparation,respectively.