A: Infrared Absorption á197Kñ.

B: Ultraviolet Absorption á197Uñ—

Solution: 25µg per mL.

Medium: 0.1Nhydrochloric acid.

Test solution: 50mg,previously dried,per mL,in 0.3Nhydrochloric acid.

Standard solutions— Dissolve an accurately weighed quantity of USP Levonordefrin RSin a mixture of methanol and glacial acetic acid (96:4)to obtain a Standard stock solution having a known concentration of 5mg per mL.Dilute this solution quantitatively with a mixture of methanol and glacial acetic acid (96:4)to obtain Standard solutions,designated below by letter,having the following compositions:

Test solution— Dissolve an accurately weighed quantity of Levonordefrin in a mixture of methanol and glacial acetic acid (96:4)to obtain a solution containing 50mg per mL.

Procedure— Apply separately 5µLof the Test solutionand 5µLof each Standard solutionto a suitable thin-layer chromatographic plate (see Chromatography á621ñ)coated with 0.25-mm layer of chromatographic silica gel mixture.Position the plate in a chromatographic chamber,and develop the chromatograms in a solvent system consisting of a mixture of n-butyl alcohol,water,and glacial acetic acid (70:20:10)until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,mark the solvent front,and allow the solvent to evaporate in warm,circulating air.Examine the plate under short-wavelength UVlight.Expose the plate to iodine vapors,and examine again.Compare the intensities,observed by both visualizations,of any secondary spots observed in the chromatogram of the Test solutionwith those of the principal spots in the chromatograms of the Standard solutions:the sum of the intensities of secondary spots obtained from the Test solutioncorresponds to not more than 1.0%of related compounds,with no single impurity corresponding to more than 0.5%.