A: Transfer a quantity of finely powdered Tablets,equivalent to about 10mg of loperamide hydrochloride,to a test tube,add 20.0mLof isopropyl alcohol,shake by mechanical means for 1minute,and allow to settle.Pipet 9.0mLof the supernatant into a 10-mLvolumetric flask,and dilute with 0.1Nhydrochloric acid to volume.The solution so obtained meets the requirements for Identificationtest Bunder Loperamide Hydrochloride.

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: 0.01Nhydrochloric acid;900mL.

Apparatus 2: 50rpm.

Time: 30minutes.

Mobile phase and Chromatographic system—Proceed as directed in the Assay.

Procedure— Separately inject equal volumes (about 50µL)of a filtered portion of the solution under test into the chromatograph,record the chromatogram,and measure the response for the major peak.Calculate the quantity of C29H33ClN2O2·HCl dissolved in comparison with a Standard solution having a known concentration of USP Loperamide Hydrochloride RSin the same Mediumand similarly chromatographed.

Tolerances— Not less than 80%(Q)of the labeled amount of C29H33ClN2O2·HCl is dissolved in 30minutes.

Buffer solution— Transfer 3.0g of triethylamine hydrochloride and 1.0mLof phosphoric acid to a 1-liter flask,add 550mLof water,and mix.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and Buffer solution(45:55).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Loperamide Hydrochloride RSin water to obtain a solution having a known concentration of about 0.2mg per mL.Transfer 10.0mLof this solution to a 250-mLvolumetric flask,add 5.0mLof 5%phosphoric acid solution and 25mLof methanol,dilute with water to volume,and mix.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 16mg of loperamide hydrochloride,to a 2000-mLvolumetric flask.Add 40mLof 5%phosphoric acid solution and 200mLof methanol,dilute with water to volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 214-nm detector and a 4-mm ×8-cm column that contains 5-µm packing L7.The flow rate is about 2mLper minute.Chromatograph the Standard preparation,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 20µL)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 loperamide hydrochloride (C29H33ClN2O2·HCl)in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Loperamide Hydrochloride RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.