Test solution: 10mg per mL,in dimethylformamide.

Solution A— Prepare a filtered and degassed mixture of 5.0mLof morpholine with 995mLof water,and adjust with phosphoric acid to a pHof 7.0.

Solution B— Prepare a filtered and degassed mixture of methanol,acetonitrile,and tetrahydrofuran (1:1:1).Make adjustments if necessary (seeSystem Suitability underChromatography á621ñ).

Mobile phase— Use variable mixtures ofSolution AandSolution Bas directed forChromatographic system (seeSystem Suitability underChromatography á621ñ).

Standard solution 1— Dissolve an accurately weighed quantity of USP Pergolide Mesylate RSin methanol,and dilute quantitatively,and stepwise if necessary,with methanol to obtain a solution having a known concentration of about 30µg per mL.

Standard solution 2— Dilute 10.0mLofStandard solution 1to 50mLwith methanol.

Test solution— Transfer about 60mg of Pergolide Mesylate,accurately weighed,to a 10-mLvolumetric flask,dissolve in and dilute with methanol to volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 280-nm detector and a 4.6-mm ×25-cm column that contains base-deactivated packing L1.The flow rate is about 1mLper minute.The column temperature is maintained at 40.The chromatograph is programmed as follows. ChromatographStandard solution 1,and record the peak responses as directed forProcedure:the column efficiency is not less than 10,000theoretical plates;the tailing factor is not more than 1.5;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)ofStandard solution 1,Standard solution 2,theTest solution,and a methanol blank into the chromatograph,record the chromatograms,and measure all of the peak responses.Disregard the contributions due to any peaks found in the methanol blank.The sum of the peak responses,excluding that of pergolide,from theTest solution is not more than the pergolide peak response obtained from Standard solution 1(0.5%),and no single peak response is more than the pergolide peak response obtained fromStandard solution 2(0.1%).

Solvent: dimethylformamide.[NOTE—Do not add sodium sulfate.]

Diluent— Dissolve 5mg of methionine in 500mLof 0.01Nhydrochloric acid.Add 500mLof methanol,and mix.

Mobile phase— Prepare a solution of 0.009Msodium 1-octanesulfonate containing 1.0mLof glacial acetic acid per liter.Prepare a filtered and degassed mixture of this solution,methanol,and acetonitrile (2:1:1).Make adjustments if necessary (seeSystem Suitability under Chromatography á621ñ).

Resolution solution— Dissolve about 4mg of USP Pergolide Sulfoxide RSand 8mg of USP Pergolide Mesylate RSin 50mLof Diluent.

Standard preparation— Dissolve an accurately weighed quantity of USP Pergolide Mesylate RSinDiluent,and dilute quantitatively,and stepwise if necessary,withDiluent to obtain a solution having a known concentration of about 0.13mg per mL.

Assay preparation— Transfer about 6.5mg of Pergolide Mesylate,accurately weighed,to a 50-mLvolumetric flask,dissolve in and dilute withDiluent to volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 280-nm detector and a 4.6-mm ×25-cm column that contains base-deactivated packing L7.The flow rate is about 1mLper minute.The column temperature is maintained at 40.Chromatograph theResolution solution,and record the peak responses as directed for Procedure:the resolution,R,between pergolide sulfoxide and pergolide is not less than 12.0.Chromatograph theStandard preparation,and record the peak responses as directed forProcedure:the tailing factor is not more than 1.5;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of theStandard preparation and theAssay preparation into the chromatograph,record the chromatograms,and measure the responses for the pergolide peaks.Calculate the quantity,in mg,of C19H26N2S·CH4O3Sin the portion of Pergolide Mesylate taken by the formula: in which Cis the concentration,in mg per mL,of USP Pergolide Mesylate RSin theStandard preparation;and rUand rSare the peak responses obtained from theAssay preparation and theStandard preparation,respectively.