Adsorbent ,Developing solvent system,and Spray reagent—Proceed as directed for Related compoundstest.

Application volume: 25µL.

Standard solution— Prepare a solution of USP Ursodiol RSin methanol containing about 1mg per mL.

Test solution— Transfer a quantity of finely powdered Tablets,equivalent to about 25mg of ursodiol,to a conical flask.Add 25.0mLof methanol,and mix for 20minutes.Centrifuge this solution for 10minutes at 4000rpm,and use the clear supernatant.

Procedure— Proceed as directed for Related compoundstest.The principal indigo-colored spot observed in the chromatogram of the Test solutioncorresponds in color and in RFvalue to that in the chromatogram of the Standard solution.

Medium: simulated intestinal fluid TS,prepared without pancreatin and adjusted with 0.1Nsodium hydroxide or 0.1Nhydrochloric acid to a pHof 8.0;900mL.

Apparatus 2: 75rpm.

Time: 45minutes.

Mobile phase and Chromatographic system—Prepare as directed in the Assay.

Procedure— Inject a volume (about 25µL)of a filtered portion of the solution under test into the chromatograph,record the chromatogram,and measure the heights of responses for the major peaks.Calculate the quantity of C24H40O4dissolved in comparison with a Standard solution having a known concentration of USP Ursodiol RSin the same Mediumand similarly chromatographed.

Tolerances— Not less than 80%(Q)of the labeled amount of C24H40O4is dissolved in 45minutes.

Adsorbent: 0.25-mm layer of chromatographic silica gel mixture (see Chromatography á621ñ),activated for at least 4hours at 105.

Developing solvent system: a mixture of chloroform,acetone,and acetic acid (7:2:1).

Standard solution 1— Prepare a solution of USP Ursodiol RSin methanol containing 20µg per mL.

Standard solution 2— Prepare a solution of lithocholic acid in methanol containing 10µg per mL.

Standard solution 3— Prepare a solution of chenodeoxycholic acid in methanol containing 300µg per mL.

Test solution— Transfer a quantity of finely powdered Tablets,equivalent to about 250mg of ursodiol,to a conical flask.Add 25.0mLof methanol,and mix for 20minutes.Centrifuge this solution for 20minutes at 4000rpm,and use the clear supernatant.

Application volume: 25µLeach of Standard solution 1,Standard solution 2,and Standard solution 3,and 50µLof the Test solution.

Spray reagent— Dissolve about 2.5g of phosphomolybdic acid in 50mLof glacial acetic acid,add 2.5mLof concentrated sulfuric acid,and mix well.

Procedure— Proceed as directed for Thin-Layer Chromatographyunder Chromatography á621ñ.Spray the plate lightly with Spray reagent.Dry the plate by heating at 105for about 7minutes.The spot due to lithocholic acid observed in the chromatogram of the Test solution,if present,is not greater in size and intensity than that obtained from Standard solution 2(0.05%).The spot due to chenodeoxycholic acid observed in the chromatogram of the Test solution,if present,is not greater in size and intensity than that obtained from Standard solution 3(1.5%).No other unidentified spot observed in the chromatogram of the Test solutionis greater in size and intensity than the spot obtained from Standard solution 1(0.1%).

Mobile phase— Prepare a filtered and degassed mixture of methanol,water,and phosphoric acid (77:23:0.6).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Internal standard solution— Dissolve an accurately weighed quantity of propylparaben in Mobile phaseto obtain a solution having a known concentration of about 3.75mg per mL.

Standard preparation— Dissolve an accurately weighed quantity of USP Ursodiol RSin Internal standard solutionto obtain a solution having a known concentration of about 3.75mg per mL.

Assay preparation— Weigh and finely powder 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 37.5mg of ursodeoxycholic acid,to a glass-stoppered conical flask.Add 10.0mLof Internal standard solution,and shake by mechanical means for 15minutes.Sonicate at 40for an additional 15minutes,and filter.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a differential refractive index detector and a 4.6-mm ×25-cm column that contains packing L7.The flow rate is about 1.0mLper minute.The detector temperature is maintained at 40.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative retention times are about 0.73for propylparaben and 1.0for ursodiol;the resolution,R,between ursodiol and propylparaben is not less than 3.0;the column efficiency is not less than 1600theoretical plates;the tailing factor is not more than 2.0;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of ursodiol (C24H40O4)in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Ursodiol RSin the Standard preparation;and RUand RSare the peak response ratios obtained from the Assay preparationand the Standard preparation,respectively.