A: Stir a portion of the Capsule contents in acetone to prepare a solution containing about 1mg of phentermine hydrochloride per mL,and filter using an acetone resistant filter.Transfer 1mLof the clear filtrate to a mortar containing about 200mg of potassium bromide,triturate with a pestle,and air-dry to allow the acetone to evaporate.Place in an oven at 125for 30minutes to dry the mixture:the IRabsorption spectrum of a potassium bromide dispersion prepared from the residue exhibits maxima only at the same wavelengths as that of a similar preparation of USP Phentermine Hydrochloride RS.

B: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

Medium: water;900mL.Use 500mLfor Capsules containing 15mg of phentermine hydrochloride or less.

Apparatus 2: 50rpm.

Time: 45minutes.

Procedure— Determine the amount of C10H15N·HCl dissolved,employing the procedure set forth in the Assay,making any necessary modifications including concentration of the analyte in the volume of test solution taken.

Tolerances— Not less than 75%(Q)of the labeled amount of C10H15N·HCl is dissolved in 45minutes.

Mobile phase— Dissolve 1.1g of sodium 1-heptanesulfonate in 575mLof water.Add 25mLof dilute glacial acetic acid (14in 100)and 400mLof methanol.Adjust dropwise,if necessary,with glacial acetic acid to a pHof 3.3±0.1.Filter through a 0.5-µm membrane filter.The volume of methanol may be adjusted to provide a suitable retention time for phentermine hydrochloride (about 8minutes).

Standard preparation— Using an accurately weighed quantity of USP Phentermine Hydrochloride RS,prepare a solution in 0.04Mphosphoric acid having a known concentration of about 0.4mg per mL.

Assay preparation— Remove,as completely as possible,the contents of not fewer than 20Capsules,and weigh.Transfer an accurately weighed portion of the mixed powder,equivalent to about 20mg of phentermine hydrochloride,to a 50-mLvolumetric flask.Add 40mLof 0.04Mphosphoric acid,and sonicate for 15minutes.Dilute with 0.04Mphosphoric acid to volume,and mix.Filter through a 0.5-µm membrane filter,discarding the first few mLof the filtrate.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The flow rate is about 2mLper minute.Chromatograph three replicate injections of the Standard preparation,and record the peak response as directed for Procedure:the relative standard deviation is not more than 2.0%.

Procedure— Separately inject equal volumes (about 50µL)of the Standard preparationand the Assay preparationinto the chromatograph by means of a suitable sampling valve,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C10H15N·HCl in the portion of Capsules taken by the formula: in which Cis the concentration,in mg per mL,of USP Phentermine Hydrochloride RSin the Standard preparation,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.