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

(Official January 1, 2007)

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 per mL and 0.02 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— Using a “to contain” pipet, transfer 2.5 mL of Injection to a 50-mL volumetric flask. Rinse the pipet with several portions of Mobile phase, and collect the rinses in the same flask. Dilute with Mobile phase to volume, and mix. Pipet 5.0 mL of this solution into a 50-mL volumetric flask, dilute with Mobile phase to volume, and mix.

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 mL of Injection taken by the formula: in which C is the concentration, in mg per mL, of USP Dolasetron Mesylate RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.