A: Infrared Absorption á197Kñ.

B: Ultraviolet Absorption á197Uñ—

Test solution: 10mg per mL,in chloroform.

Standard dilutions— Dissolve an accurately weighed quantity of USP Stanozolol RSin a mixture of chloroform and methanol (9:1)to obtain a solution having a known concentration of about 20mg per mL.Dilute this solution with the same medium to obtain Standard dilutionshaving known concentrations of about 50,100,200,and 400µg per mL,respectively.

Procedure— Score a 20-×20-cm thin-layer chromatographic plate coated with a 0.25-mm layer of chromatographic silica gel mixture (binder-free)into channels 10mm wide.Apply 10-µLportions,in two 5-µLincrements,of a test solution prepared by dissolving Stanozolol in a mixture of chloroform and methanol (9:1)to obtain a solution containing about 20mg per mL,and of each of the four Standard dilutionsin the center of the channels at points about 2.5cm from one edge of the plate.Develop the plate in a suitable chamber,lined with filter paper and previously equilibrated with 200mLof a mixture of chloroform and methanol (188:12),for 15minutes,taking care to ensure that the filter paper has been wetted completely with the solvent mixture.Allow the plate to develop until the solvent front has moved about 15cm above the line of application.Remove the plate,and allow the solvent to evaporate completely.Spray it with 20%sulfuric acid,and heat in an oven at 100for 15minutes.Examine the plate under long-wavelength UVlight:the channel for the test solution exhibits its principal spot at the same RFvalue as the spots for the Standard dilutions.Estimate the concentration of any spots in the channel for the test solution,other than the principal spot,by comparison with the spots from the Standard dilutions.The spots from the 50-,100-,200-,and 400-µg-per-mLdilutions correspond to 0.25%,0.5%,1.0%,and 2.0%of chromatographic impurities,respectively,and the sum of the chromatographic impurities in the test solution is not greater than 2.0%.

Solvent— Use dimethyl sulfoxide.