A: Infrared Absorption á197Kñ.

B: Ultraviolet Absorption á197Uñ—

C: Dissolve 1g in 10mLof water,add 10mLof saturated sodium carbonate solution,and mix.Separate the precipitate by vacuum filtration,using a medium-porosity,sintered-glass filter,and wash with three 5-mLportions of ice-cold water.Dry the crystals at 80for 1hour:the phenylpropanolamine so obtained melts between 101and 104(see Melting Range or Temperature á741ñ).

Mobile phase— Prepare a filtered and degassed mixture of water,acetonitrile,phosphoric acid,and triethylamine (950:50:8:5).Make adjustments if necessary (see System suitabilityunder Chromatography á621ñ).

System suitability solution— Dissolve suitable quantities of USP Phenylpropanolamine Hydrochloride RSand USP Dextroamphetamine Sulfate RSin water to obtain a solution containing about 5µg of each per mL.

Amphetamine stock solution— Dissolve an accurately weighed quantity of USP Dextroamphetamine Sulfate RSin water,and dilute quantitatively,and stepwise if necessary,with water to obtain a solution having a known concentration of about 2.5µg per mL.

Phenylpropanolamine stock solution— Transfer about 2.5g of Phenylpropanolamine Hydrochloride,accurately weighed,to a 10-mLvolumetric flask,dilute with water to volume,and dissolve,using sonication if necessary.

Standard solution— Transfer 4.0mLof Phenylpropanolamine stock solution,accurately measured,to a 10-mLvolumetric flask,add 4.0mLof Amphetamine stock solution,dilute with water to volume,and mix to obtain a solution having known concentrations of about 100mg per mLand 1µg per mL,respectively.

Test solution— Transfer about 4.0mLof Phenylpropanolamine stock solution,accurately measured,to a 10-mLvolumetric flask,dilute with water to volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 206-nm detector and a 4.6-mm ×25-cm column that contains 5-µm,base-deactivated packing L1.The flow rate is about 1mLper minute.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the relative retention times are 1.0for phenylpropanolamine and 2.1for amphetamine;the resolution,R,between phenylpropanolamine and amphetamine is not less than 15;and the column efficiency is not less than 10,000theoretical plates.Chromatograph the Standard solution,and record the peak responses as directed for Procedure:the relative standard deviation of the amphetamine peak for replicate injections is not more than 3.0%.

Procedure— Separately inject equal volumes (about 5µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the responses at the locus of the amphetamine peak.Calculate the percentage of amphetamine hydrochloride in the portion of Phenylpropanolamine Hydrochloride taken by the formula: in which 171.67and 368.49are the molecular weights of amphetamine hydrochloride and amphetamine sulfate,respectively;CSis the concentration,in µg per mL,of USP Dextroamphetamine Sulfate RSin the Standard solution;CUis the concentration,in mg per mL,of Phenylpropanolamine Hydrochloride in the Test solution;and rUand rSare the peak responses of amphetamine obtained from the Test solutionand the Standard solution,respectively:not more than 0.001%is found.