Medium: tartaric acid solution (1 in 200); 900 mL.

Apparatus 2: 100 rpm.

Time: 30 minutes.

Procedure— Filter a portion of the solution under test into a flask. Concomitantly determine the fluorescence intensity of this solution in comparison with a Standard solution of USP Methysergide Maleate RS in the same medium having a known concentration of about 2.2 µg per mL in a fluorometer at an excitation wavelength of about 327 nm and an emission wavelength of about 428 nm, using tartaric acid solution (1 in 200) as the blank.

Tolerances— Not less than 70% (Q) of the labeled amount of C21H27N3O2·C4H4O4 is dissolved in 30 minutes.

(Official January 1, 2007)

Mobile phase— Dissolve 6.8 g of monobasic potassium phosphate in 700 mL of water, add 300 mL of acetonitrile, and mix. Filter through a 0.45-µm membrane, and degas under vacuum. Make adjustments if necessary (see System Suitability under Chromatography 621).

Solvent mixture— Dissolve 10 g of tartaric acid in 1 L of water, add 1 L of methanol, and mix.

Standard preparation— Dissolve an accurately weighed quantity of USP Methysergide Maleate RS in Solvent mixture with the help of sonication, and dilute quantitatively, and stepwise if necessary, with the same solvent to obtain a solution having a known concentration of about 0.1 mg per mL.

Assay preparation— Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 10 mg of methysergide maleate, to a 100-mL volumetric flask. Add 75 mL of Solvent mixture, and shake by mechanical means for 60 minutes. Add Solvent mixture to volume, mix, and filter through a 0.45-µm membrane, discarding the first 20 mL of the filtrate.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 318-nm detector and a 4.6-mm × 15-cm column that contains packing L7. The flow rate is about 2 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the column efficiency determined from the analyte peak is not less than 1000 theoretical plates, the tailing factor for the analyte peak is not more than 2.5, the resolution, R, between the analyte and the closest adjacent peak is not less than 1.0, and the relative standard deviation for replicate injections is not more than 2.0%.

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 responses for the major peaks. Calculate the quantity, in mg, of methysergide maleate (C21H37N3O2·C4H4O4) in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Methysergide Maleate RS in the Standard preparation;, and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.