A: Thin-Layer Chromatographic Identification Test á201ñ—

Test solution— Transfer a quantity of the contents of the Capsules,equivalent to about 10mg of loperamide hydrochloride,to a 37-mLstoppered vial,add 10mLof methanol,shake for 5minutes,and filter.

Standard solution: a solution of USP Loperamide Hydrochloride RSin methanol containing about 10mg per mL.

Application volume: 10µLof the Test solutionand 1µLof the Standard solution.

Developing solvent system: a mixture of chloroform,methanol,and formic acid (85:10:5).

Procedure— Proceed as directed in the chapter.Visualize the spots by exposing to iodine vapors.

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: pH4.7acetate buffer,prepared by mixing 200mLof 1Nacetic acid with 600mLof water,adjusting with 1Nsodium hydroxide to a pHof 4.70±0.05,diluting with water to 1000mL,and mixing;500mL.

Apparatus 1: 100rpm.

Time: 30minutes.

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

Procedure— Inject a volume (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 medium and similarly chromatographed.

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

Mobile phase— Transfer 500mLof acetonitrile to a 1000-mLvolumetric flask.Dilute with water to volume,add 20drops of phosphoric acid,mix,and filter.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Loperamide Hydrochloride RSin a mixture of acetonitrile and 0.5Nhydrochloric acid (1:1)to obtain a solution having a known concentration of about 0.2mg per mL.Transfer 5.0mLof this solution to a 100-mLvolumetric flask,dilute with a mixture of acetonitrile and water (1:1)to volume,and mix to obtain a solution having a known concentration of about 10µg per mL.

Assay preparation— Transfer,as completely as possible,the contents of not less than 20Capsules to a suitable tared container,and determine the average weight per capsule.Mix the combined contents,and transfer an accurately weighed portion of the powder,equivalent to about 20mg of loperamide hydrochloride,to a 100-mLvolumetric flask.Add about 35mLof 0.5Nhydrochloric acid and sonicate for 15minutes.Add 35mLof acetonitrile and sonicate for an additional 15minutes.Dilute with a mixture of acetonitrile and 0.5Nhydrochloric acid (1:1)to volume,mix,and filter.Transfer 5.0mLof this solution to a 100-mLvolumetric flask,dilute with a mixture of acetonitrile and water (1:1)to volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 220-nm detector and a 4-mm ×25-cm column that contains 10-µm packing L10.The flow rate is about 2mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed under Procedure:the column efficiency,N,determined from the analyte peak is not less than 1900theoretical plates,the capacity factor,K¢,is not less than 3.5,and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 50µL)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 C29H33ClN2O2·HCl in the portion of Capsules 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.