A: Infrared Absorption 197K.

B: Ultraviolet Absorption 197U—

C: It responds to the tests for Chloride 191.

Standard preparations— Dissolve an accurately weighed quantity of USP Phentermine Hydrochloride RS in chloroform to obtain Standard preparation A having a known concentration of 2 mg 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 200 mg per mL.

Procedure— Apply separately 10 µL of the Test preparation and 10 µL of each Standard preparation to a suitable thin-layer chromatographic plate (see Chromatography 621) 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 UV light. Compare the intensities of any secondary spots observed in the chromatogram of the Test preparation with those of the principal spots in the chromatograms of the Standard preparations: the sum of the intensities of secondary spots obtained from the Test preparation corresponds to not more than 1.0% of related compounds, with no single impurity corresponding to more than 0.5%.