Test specimen— Transfer a quantity of powdered Tablets,equivalent to about 200mg of dolasetron mesylate,to a capped tube.Add 10mLof acetonitrile,and shake for about 5minutes.Allow to settle,filter,and collect the filtrate in a glass vial.Evaporate the solvent at 85.Add an additional 5mLof acetonitrile to the vial,and evaporate at 85.Then evaporate to dryness in a vacuum oven at 80.Mix about 2mg of the crystals obtained with about 300mg of potassium bromide.

Medium: 0.1Nhydrochloric acid;900mL.

Apparatus 2: 50rpm.

Time: 30minutes.

Procedure— Determine the amount of C19H20N2O3·CH4O3S·H2Odissolved by employing UVabsorption at the wavelength of maximum absorbance at about 284nm on filtered portions of the solution under test,suitably diluted with Medium,in comparison with a Standard solution having a known concentration of USP Dolesetron Mesylate RSin the same Medium.

Tolerances— Not less than 80%(Q)of the labeled amount of C19H20N2O3·CH4O3S·H2Ois dissolved in 30minutes.

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 and 0.05mg per mL,respectively.

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

Assay preparation— Transfer 10Tablets to a 500-mLvolumetric flask,add about 400mLof Mobile phase,and stir vigorously with a magnetic stirrer for at least 40minutes to dissolve.Dilute with Mobile phaseto volume,mix,and allow the insoluble excipients to settle.Quantitatively dilute a portion of the supernatant with Mobile phaseto obtain a solution having a concentration of about 0.1mg of dolasetron mesylate per mL.

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 Tablet taken by the formula: in which Tis the labeled quantity,in mg,of dolasetron mesylate in the Tablet;Cis the concentration,in mg per mL,of USP Dolasetron Mesylate RSin the Standard preparation;Dis the concentration,in mg per mL,of dolasetron mesylate in the Assay preparation,based on the labeled quantity per Tablet and the extent of dilution;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.