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

Medium: 0.1 N hydrochloric acid; 900 mL.

Apparatus 2: 50 rpm.

Time: 30 minutes.

Procedure— Determine the amount of C19H20N2O3·CH4O3S·H2O dissolved by employing UV absorption at the wavelength of maximum absorbance at about 284 nm on filtered portions of the solution under test, suitably diluted with Medium, in comparison with a Standard solution having a known concentration of USP Dolasetron Mesylate RS in the same Medium.

Tolerances— Not less than 80% (Q) of the labeled amount of C19H20N2O3·CH4O3S·H2O is dissolved in 30 minutes.

Mobile phase— Proceed as directed in the Assay under Dolasetron Mesylate.

System suitability preparation— Dissolve accurately weighed quantities of USP Dolasetron Mesylate RS and indole-3-carboxylic acid in Mobile phase, and dilute quantitatively, and stepwise if necessary, with Mobile phase to obtain a solution having known concentrations of about 0.1 mg and 0.05 mg per mL, respectively.

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

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

Chromatographic system (see Chromatography 621)— Prepare as directed in the Assay under 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 20 µL) of the Standard preparation and the Assay preparation into 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 T is the labeled quantity, in mg, of dolasetron mesylate in the Tablet; C is the concentration, in mg per mL, of USP Dolasetron Mesylate RS in the Standard preparation; D is 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 rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.