Adsorbent: 0.25-mm layer of binder-free silica gel.

Test solution— Transfer a number of Tablets,equivalent to 1mg of pergolide,to a separator containing 20mLof methylene chloride and 10mLof 0.1Nsodium hydroxide.Shake until the Tablets have disintegrated,allow the layers to separate,and drain the methylene chloride layer through a small funnel containing about 1g of anhydrous sodium sulfate,collecting the filtrate in a suitable stoppered vessel.Wash the sodium sulfate with a few mLof methylene chloride,adding these washes to the filtrate,and evaporate to dryness under a stream of nitrogen.Redissolve the residue in 2mLof a mixture of methylene chloride and methanol (1:1).

Standard solution: 0.65mg per mL,in a mixture of methylene chloride and methanol (1:1).

Application volume: 20µL.

Developing solvent system: a mixture of chloroform,methanol,and ethyl acetate (8:1:1).Allow the plate to equilibrate for about 10minutes in the developing chamber prior to development.

Procedure— Proceed as directed in the chapter.Place the plate in a chamber containing iodine vapors,and locate the spots.

Medium: simulated gastric fluid TS(without enzymes)containing 20µg of L-cysteine per mL;500mL.

Apparatus 2: 50rpm.

Time: 30minutes.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile,water,and triethylamine,(21:19:0.08).Adjust with phosphoric acid to a pHof 5.0.Make adjustments if necessary (seeSystem Suitability underChromatography á621ñ).

Triethylamine phosphate suspension— Add 1.0mLof triethylamine to 500mLof acetonitrile,mix,and adjust with phosphoric acid to a pHof 5.0.Awhite precipitate will form.Stir continuously during use.

Resolution solution— Prepare a solution of USP Pergolide Mesylate RSand USP Pergolide Sulfoxide RScontaining a known amount of each equivalent to the labeled amount of pergolide in each 500mLof Medium.

Standard solution— Transfer about 16mg of USP Pergolide Mesylate RS,accurately weighed,to a 250-mLvolumetric flask,dissolve in 10.0mLof methanol,dilute withMedium to volume,and mix.Dilute this solution quantitatively and stepwise withMedium to obtain a solution having a known concentration equivalent to the labeled amount of pergolide in each 500mL.

Chromatographic system (seeChromatography á621ñ)— The liquid chromatograph is equipped with a fluorometer set to an excitation wavelength of 224nm and an emission wavelength of 350nm and with a 4.6-mm ×15-cm column that contains base-deactivated packing L10.The flow rate is about 2mLper minute.Chromatograph theResolution solution,and record the peak responses as directed forProcedure:the resolution,R,between pergolide sulfoxide and pergolide is not less than 1.0.Chromatograph theStandard solution,and record the peak responses as directed forProcedure:the relative standard deviation for replicate injections,determined from the pergolide peak,is not more than 2.0%.

Procedure— Immediately before injection,pipet 2.0mLofTriethylamine phosphate suspension,continuously stirred,into a suitable container containing 5.0mLof the solution for injection,and mix to obtain a clear solution.Separately inject equal volumes (about 200µL)of theStandard solution and filtered portions of the solutions under test into the chromatograph,record the chromatograms,and measure the areas for the major peaks.Calculate the amount,in mg,of pergolide (C19H26N2S)dissolved by the formula: in which Cis the concentration,in µg per mL,of USP Pergolide Mesylate RSin theStandard solution;314.50and 410.60are the molecular weights of pergolide and pergolide mesylate,respectively;and rUand rSare the peak areas obtained from the solution under test and theStandard solution,respectively.

Tolerances— Not less than 75%(Q)of the labeled amount of C19H26N2Sis dissolved in 30minutes.

Mobile phase,System suitability solution,Standard preparation,and Chromatographic system— Proceed as directed in the Assay.

Diluted standard preparation— Transfer 3.0mLof theStandard preparation to a 50-mLvolumetric flask.Dilute withMobile phaseto volume,and mix.

Test preparation— Use theAssay preparation.

Procedure— Separately inject equal volumes (about 100µL)of theDiluted standard preparation and theTest preparation into the chromatograph,and measure all of the peak responses.Calculate the percentage of each impurity in the Tablets by the formula: in which Cis the concentration,in µg per mL,of USP Pergolide Mesylate RSin theDiluted standard preparation;314.50and 410.60are the molecular weights of pergolide and pergolide mesylate,respectively;riis the peak response of the individual impurity obtained from theTest preparation;and rSis the peak response of pergolide obtained from theDiluted standard preparation:not more than 6.0%of pergolide sulfoxide is found;not more than 0.5%of any individual impurity,excluding pergolide sulfoxide,is found;and not more than 1.0%of total impurities,excluding pergolide sulfoxide,is found.

Mobile phase— Prepare a solution of 0.038Msodium 1-octanesulfonate containing 0.0077mg of methionine per mLand 2.45mLof glacial acetic acid per liter.Adjust with 5Nsodium hydroxide to a pHof 4.1.Prepare a filtered and degassed mixture of this solution and acetonitrile (65:35).Make adjustments if necessary (seeSystem Suitability underChromatography á621ñ).

System suitability solution— Prepare a solution of USP Pergolide Mesylate RSand USP Pergolide Sulfoxide RSinMobile phase having a known concentration of about 6.5µg per mLof pergolide mesylate and 0.1µg per mLof pergolide sulfoxide.

Standard preparation— Dissolve an accurately weighed quantity of USP Pergolide Mesylate RSinMobile phase,and dilute quantitatively and stepwise withMobile phase to obtain a solution having a known concentration of about 6.5µg per mL.

Assay preparation— Place 20whole Tablets into a suitable stoppered container,addMobile phase,shake and sonicate until the Tablets have dissolved,and quantitatively dilute to obtain a solution containing about 5µg per mLof pergolide.

Chromatographic system (seeChromatography á621ñ)— The liquid chromatograph is equipped with a fluorometer set to an excitation wavelength of 280nm and an emission wavelength of 335nm and with a 4.6-mm ×7.5-cm column that contains base-deactivated packing L7.The flow rate is about 1.5mLper minute.The column temperature is maintained at 35.Chromatograph theSystem suitability solution,and record the peak responses as directed for Procedure:the resolution,R,between pergolide sulfoxide and pergolide is not less than 12.0;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 100µL)of theStandard preparation and theAssay preparation into the chromatograph,and measure the responses for the major peaks.Calculate the quantity,in mg,of pergolide (C19H26N2S)in the portion of Tablets taken by the formula: in which Cis the concentration,in µg per mL,of USP Pergolide Mesylate RSin theStandard preparation;314.50and 410.60are the molecular weights of pergolide and pergolide mesylate,respectively;and rUand rSare the peak responses obtained from theAssay preparation and theStandard preparation,respectively.