A: Infrared Absorption á197Kñ.

B: Ultraviolet Absorption á197Uñ—

C: It responds to the tests for Chloride á191ñ.

Standard preparations— Dissolve an accurately weighed quantity of USP Phentermine Hydrochloride RSin chloroform to obtain Standard preparation Ahaving a known concentration of 2mg per mL.Dilute this solution quantitatively with chloroform to obtain Standard preparations,designated below by letter,having the following compositions:

Test preparation— Dissolve an accurately weighed quantity of Phentermine Hydrochloride in chloroform to obtain a solution containing 200mg per mL.

Procedure— Apply separately 10µLof the Test preparationand 10µLof each Standard preparationto a suitable thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 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 chloroform,cyclohexane,and diethylamine (50:40:10)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 air.Examine the plate under short-wavelength UVlight.Compare the intensities of any secondary spots observed in the chromatogram of the Test preparationwith those of the principal spots in the chromatograms of the Standard preparations:the sum of the intensities of secondary spots obtained from the Test preparationcorresponds to not more than 1.0%of related compounds,with no single impurity corresponding to more than 0.5%.