Mobile phase,Standard solution,System suitability solution,and Chromatographic system— Proceed as directed in the test for Limit of ondansetron related compound Dunder Ondansetron Hydrochloride.

Test solution— Transfer an accurately measured volume of Injection,equivalent to about 10mg of ondansetron,to a 25-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Procedure— Separately inject equal volumes (about 20µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity of ondansetron related compound Din the volume of Injection taken by the formula: in which Vis the volume,in mL,of Injection taken;CSis the concentration,in µg per mL,of ondansetron related compound Din the Standard preparation;CAis the concentration,in mg per mL,of ondansetron in the Injection,as determined in the Assay;and rUand rSare the peak responses obtained from the Test preparationand the Standard preparation,respectively:not more than 0.12%is found.

Mobile phase andChromatographic system— Proceed as directed in the Assay.

Standard solution— Proceed as directed for Standard preparationin the Assay.

Test solution— Use the Assay preparation.

Procedure— Inject a volume (about 10µL)of the Test solutioninto the chromatograph,record the chromatogram,and measure the peak responses.Calculate the percentage of each impurity in the volume of Injection taken by the formula: in which riis the peak response for each impurity;and rsis the sum of the responses of all of the peaks:not more than 0.2%of any individual impurity is found,and the total of all impurities is not more than 0.5%.

Mobile phase— Prepare a filtered and degassed mixture of 0.02Mmonobasic potassium phosphate (previously adjusted with 1Msodium hydroxide to a pHof 5.4),and acetonitrile (50:50).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Ondansetron Hydrochloride RSin Mobile phase,and dilute quantitatively,and stepwise if necessary,with Mobile phaseto obtain a solution having a known concentration of about 0.1mg per mL.

System suitability solution— Dissolve suitable quantities of USP Ondansetron Hydrochloride RSand USP Ondansetron Related Compound A RSin Mobile phase,and dilute quantitatively,and stepwise if necessary,with Mobile phaseto obtain a solution containing about 0.1mg per mLand 50µg per mL,respectively.

Assay preparation— Transfer an accurately measured volume of Injection,equivalent to about 2mg of ondansetron,to a 25-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 216-nm detector and a 4.6-mm ×20-cm column that contains packing L10.The flow rate is about 1.5mLper minute.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the relative retention times are about 1.0for ondansetron and 1.1for ondansetron related compound A;and the resolution,R,between ondansetron related compound Aand ondansetron is not less than 1.5.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 1.5%.

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 ondansetron (C18H19N3O)in each mLof the Injection taken by the formula: in which 293.36and 329.82are the molecular weights of ondansetron and anhydrous ondansetron hydrochloride,respectively;Cis the concentration,in mg per mL,on the anhydrous basis,of USP Ondansetron Hydrochloride RSin the Standard preparation;Vis the volume,in mL,of Injection taken;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.