A: Empty the contents of 2Capsules into a beaker,add 20mLof methanol,and swirl for approximately 2minutes.Filter through a filter paper,and evaporate the methanol solution with a current of cool air to dryness:the IRabsorption spectrum of a potassium bromide dispersion of the residue so obtained exhibits maxima only at the same wavelengths as that of a similar preparation of USP Nizatidine RS.

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

Medium: water;900mL.

Apparatus 2: 50rpm.

Time: 30minutes.

Procedure— Determine the amount of C12H21N5O2S2dissolved from UVabsorbances at the wavelength of maximum absorbance at about 314nm using filtered portions of the solution under test,diluted with water if necessary,in comparison with a Standard solution having a known concentration of USP Nizatidine RSin the same medium.

Tolerances— Not less than 75%(Q)of the labeled amount of C12H21N5O2S2is dissolved in 30minutes.

Buffer solutionand Mobile phase— Prepare as directed in the Assayunder Nizatidine.

Standard solution— Dissolve an accurately weighed quantity of USP Nizatidine RSin Mobile phaseand dilute quantitatively,and stepwise if necessary,with Mobile phaseto obtain a solution having a known concentration of about 40µg per mL.

Test solution— Remove as completely as possible the contents of not less than 20Capsules,and mix.Transfer an accurately weighed portion of the powder,equivalent to about 200mg of nizatidine,to a 100-mLvolumetric flask,add 50mLof Mobile phase,and sonicate for about 3minutes.Dilute with Mobile phaseto volume,mix,and filter.

System suitability solution— Prepare a solution of nizatidine and phenol in Mobile phasecontaining 40µg of each per mL.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 230-nm detector and a 4.6-mm ×15-cm column that contains 5-µm packing L1.The flow rate is about 1mLper minute.Chromatograph the System suitability solution,and record the peak responses as directed under Procedure:the resolution,R,between the nizatidine and phenol peaks is not less than 1.5,the tailing factor for the nizatidine peak is not greater than 1.5,and the relative standard deviation of the nizatidine peak for replicate injections is not more than 2%.

Procedure— Chromatograph about 10µLof the Standard solutionand the Test solution,and run the chromatograph for twice the elution time of nizatidine.Record the chromatograms,and measure the peak responses.Calculate the percentage of each impurity in the portion of Capsules taken by the formula: in which riis the response of each impurity peak in the Test solution,and rsis the response of the nizatidine peak in the Standard solution:not more than 0.5%of any individual impurity and not more than 1.5%of total impurities is found.

Buffer solutionand Mobile phase— Prepare as directed in the Assayunder Nizatidine.

Internal standard solution— Prepare a solution of phenol in Mobile phasehaving a concentration of 0.1mg per mL.

Standard preparation— Dissolve an accurately weighed quantity of USP Nizatidine RSin Internal standard solutionto obtain a solution having a known concentration of 0.1mg per mL.

Assay preparation— Weigh accurately not less than 10Capsules.Remove as completely as possible the contents of the Capsules,and mix the combined contents.Clean and accurately weigh the Capsule shells,and calculate the net weight of the Capsule contents.Transfer an accurately weighed portion of the mixed Capsule contents equivalent to about 500mg of nizatidine to a 500-mLvolumetric flask,add 200mLof Internal standard solution,and sonicate for a few minutes.Cool,dilute with Internal standard solutionto volume,and mix.Filter a portion of the solution,transfer 1.0mLof the filtered solution to a 10-mLvolumetric flask,dilute with Internal standard solutionto volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 230-nm detector and a 4.6-mm ×15-cm column that contains 5-µm packing L1.The flow rate is about 1mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the resolution,R,between nizatidine and the internal standard phenol,is not less than 3;the tailing factor,T,for the nizatidine peak is not more than 1.6;and the relative standard deviation for replicate injections is not more than 1.5%.

Procedure— Separately inject equal volumes (about 25µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.The relative retention times are about 0.7for phenol and 1.0for nizatidine.Calculate the quantity,in mg,of C12H21N5O2S2in the portion of Capsules taken by the formula: in which Cis the concentration,in mg per mL,of USP Nizatidine RSin the Standard preparation,and RUand RSare the ratios of the peak response of the nizatidine to that of the internal standard for the Assay preparationand the Standard preparation,respectively.