A: Infrared Absorption á197Kñ.

B: Ultraviolet Absorption á197Uñ—

Test solution: 20mg per mL,in dioxane.

Mobile phase— Dissolve 0.8g of ammonium nitrate in 300mLof water,add 700mLof acetonitrile,and mix.

Internal standard solution— Prepare a solution of testosterone benzoate in tetrahydrofuran containing 2.0mg per mL.

Standard preparation— Accurately weigh about 10mg of USP Estradiol Cypionate RS,and transfer to a 10-mLvolumetric flask.Add Internal standard solutionto volume,and shake vigorously to dissolve.

Assay preparation— Using 10mg of Estradiol Cypionate,accurately weighed,proceed as directed under Standard preparation.

Procedure— Separately inject 10-µLaliquots of the Assay preparationand the Standard preparationinto a suitable high-pressure liquid chromatograph fitted with a 280-nm detector,a 4-mm ×30-cm column containing packing L1and operated at room temperature.The Mobile phaseis maintained at a pressure and flow rate capable of giving the required resolution and a suitable elution time.In a suitable system,the resolution factor R(see Chromatography á621ñ)is not less than 3.0between the peaks for estradiol cypionate and the internal standard.Five replicate injections of the Standard preparationshow a relative standard deviation that is not more than 1.5%.Calculate the quantity,in mg,of C26H36O3in the portion of Estradiol Cypionate taken by the formula: in which Cis the concentration,in mg per mL,of USP Estradiol Cypionate RSin the Standard preparation;and RUand RSare the ratios of the peak responses of the estradiol cypionate and internal standard peaks obtained from the Assay preparationand the Standard preparation,respectively.