Test specimen— Transfer a portion of Injection,equivalent to about 100mg of dolasetron mesylate,to a 150-mLbeaker.Add about 20mLof water and 10mLof a sodium hydroxide solution (1in 10).Mix,and allow to stand at room temperature for 30minutes.Pass through a filtering crucible with fritted disk having a medium porosity,using about 100mLof water to aid in the transfer.Dry the precipitate in a vacuum oven at 105for 4hours.Prepare a 1.5%mixture of the dried powder with potassium bromide.

Mobile phase— Proceed as directed in the Assayunder Dolasetron Mesylate.

System suitability preparation— Dissolve accurately weighed quantities of USP Dolasetron Mesylate RSand indole-3-carboxylic acid in Mobile phase,and dilute quantitatively,and stepwise if necessary,with Mobile phaseto obtain a solution having known concentrations of about 0.1mg per mLand 0.02mg per mL,respectively.

Standard preparation— Dissolve an accurately weighed quantity of USP Dolasetron Mesylate RSin Mobile phaseto obtain a solution having a known concentration of about 0.1mg per mL.

Assay preparation— Using a “to contain”pipet,transfer 2.5mLof Injection to a 50-mLvolumetric flask.Rinse the pipet with several portions of Mobile phase,and collect the rinses in the same flask.Dilute with Mobile phaseto volume,and mix.Pipet 5.0mLof this solution into a 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Chromatographic system (see Chromatography á621ñ)— Prepare as directed in the Assayunder Dolasetron Mesylate.Chromatograph the System suitability preparation,and record the peak responses as directed for Procedure:the resolution,R,between indole-3-carboxylic acid and dolasetron mesylate is not less than 4;and the tailing factor for the dolasetron mesylate peak is not more than 1.8.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative standard deviation for replicate injections is not more than 1.5%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the areas for the major peaks.Calculate the quantity,in mg,of dolasetron mesylate (C19H20N2O3·CH4O3S·H2O)in each mLof Injection taken by the formula: in which Cis the concentration,in mg per mL,of USP Dolasetron Mesylate RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.