A: Aportion of finely powdered Tablets meets the requirements for Identificationtest Aunder Phentermine Hydrochloride Capsules.

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 Tablets containing 15mg of phentermine hydrochloride or less.

Apparatus 2: 50rpm.

Time: 45minutes.

Ion-pair solution— Dissolve 1.1g of sodium 1-heptanesulfonate in 1liter of water.Add 3.5mLof glacial acetic acid,and mix.

Mobile phase— Prepare a filtered and degassed mixture of methanol and Ion-pair solution(21:19).Adjust with phosphoric acid to a pHof 2.5.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard solution— Dissolve an accurately weighed quantity of USP Phentermine Hydrochloride RSin water,and dilute quantitatively,and stepwise if necessary,with water to obtain a solution having a known concentration approximately equivalent to the Test solution.

Test solution— Use a filtered portion of the pooled sample under test.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 208-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 1mLper minute.Chromatograph the Standard solution,and record the peak responses as directed for Procedure:the tailing factor is not more than 2.0;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 25µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the peak responses.Determine the amount,in mg,of phentermine hydrochloride (C10H15N·HCl)dissolved by the formula: in which Vis the volume of dissolution media used per vessel;Cis the concentration,in mg per mL,of USP Phentermine Hydrochloride RSin the Standard solution;and rUand rSare the peak responses obtained from the Test solutionand the Standard solution,respectively.

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

Procedure for content uniformity— Proceed as directed in the Assay,except to prepare the Test preparationsas follows.Transfer 1Tablet to each of 10suitable containers,add 1mLof water and 10mLof Internal standard solutionto each,mix,sonicate for about 10minutes after each Tablet has disintegrated,and filter.

Mobile phase— Prepare a suitably degassed solution containing 0.03%diethylamine in methanol.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Internal standard solution— Prepare a solution of caffeine in Mobile phasehaving a final concentration of about 0.02mg per mL.

Standard preparation— Transfer an accurately weighed amount of USP Phentermine Hydrochloride RS,equivalent to about 7.5mg of phentermine hydrochloride,to a 10-mLvolumetric flask.Add Internal standard solutionto volume,and mix.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 7.5mg,to a suitable flask.Pipet 10.0mLof Internal standard solutioninto the flask.Insert the stopper,mix,and sonicate for about 10minutes.Pass through a filter having a 0.5-µm porosity.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative retention times are about 0.5for caffeine and 1.0for phentermine;the resolution,R,between caffeine and phentermine is not less than 4;the column efficiency determined from the analyte peak is not less than 2000theoretical plates;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of phentermine hydrochloride (C10H15N·HCl)in the portion of Tablets 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 response ratios of phentermine to the internal standard obtained from the Assay preparationand the Standard preparation,respectively.