Medium: methanol.

Procedure— Powder a portion of Capsule contents equivalent to 5mg of lansoprazole.Add 5mLof methanol,shake well,and centrifuge.To 0.1mLof the supernatant,add 10mLof methanol.

Acid stage medium: 0.1Nhydrochloric acid;500mL.

Apparatus 2: 75rpm.

Time: 60minutes.

Procedure— Withdraw a 25-mLaliquot and then proceed immediately as directed forTest solution in theBuffer stage leaving the remaining 475mLin the vessel for use in the Buffer stage.Using a filtered portion of the aliquot,determine the amount of C16H14F3N3O2Sdissolved by employing UVabsorption at the wavelength of maximum absorbance at about 306nm,usingAcid stage medium as the blank.Concomitantly determine the absorbance of theAcid stage test solution in comparison with a solution of USP Lansoprazole RS,having a known concentration equivalent to about 8%of the labeled amount of lansoprazole dissolved per 500mLofAcid stage medium.Avolume of methanol not to exceed 0.5%of the total volume of the Standard solution may be used to dissolve USP Lansoprazole RSprior to dilution withAcid stage medium.

Tolerances— Not more than 10%of the labeled amount of C16H14F3N3O2Sis dissolved in 60minutes.

Buffer concentrate— Transfer 65.4g of monobasic sodium phosphate,28.2g of sodium hydroxide,and 12g of sodium dodecyl sulfate to a suitable container,and add enough water to dissolve.Dilute with water to 4L,and mix well.

Blank solution— Prepare a mixture ofAcid stage medium andBuffer concentrate (19:17).Adjust,if necessary,with either phosphoric acid or sodium hydroxide to a pHof 6.8.

Test solution— Add 425mLofBuffer concentrate to the remaining 475mLof solution in each vessel from theAcid stage.Adjust,if necessary,with either phosphoric acid or sodium hydroxide to a pHof 6.8.

Apparatus 2: 75rpm.

Time: 60minutes.

Procedure— Determine the amount of C16H14F3N3O2Sdissolved in filtered portions of theTest solution,using the difference between the absorbances at the wavelengths of about 286nm and 650nm,withBlank solution as the blank.Concomitantly determine the absorbances of theTest solution in comparison with the solution of USP Lansoprazole RShaving a known concentration equivalent to about 70%of the labeled amount of lansoprazole dissolved in 900mLofBlank solution.An amount of methanol not to exceed 2%of the total volume of the Standard solution may be used to dissolve USP Lansoprazole RSprior to dilution withBlank solution.

Tolerances— Not less than 80%(Q)of the labeled amount of C16H14F3N3O2Sis dissolved in 60minutes.

Test solution— Transfer the contents of 1Capsule to a 100-mLvolumetric flask,add 30mLof 0.1Msodium hydroxide,and sonicate to disintegrate.Add 65mLof acetonitrile,cool,and dilute with acetonitrile to volume.Centrifuge a portion of the suspension and pass through a membrane filter having a 0.5-µm or finer porosity.Quantitatively dilute a volume of the filtrate with a mixture of acetonitrile and 0.1Msodium hydroxide (7:3)to obtain a solution containing about 0.012mg of lansoprazole per mL.

Procedure— Concomitantly determine the absorbances of theTest solution and a solution of USP Lansoprazole RSin the same medium and having a known concentration of about 0.012mg of lansoprazole per mL,in 1-cm cells,at the wavelength of maximum absorbance at about 294nm,with a suitable spectrophotometer,using a mixture of acetonitrile and 0.1Msodium hydroxide (7:3)as the blank.Calculate the quantity,in mg,of C16H14F3N3O2Sin the Capsule taken by the formula: in which Lis the labeled quantity of lansoprazole in the Capsule;Cis the concentration,in mg per mL,of USP Lansoprazole RSin theStandard solution;Dis the concentration,in mg per mL,of lansoprazole in theTest solution,based on the labeled quantity of lansoprazole per Capsule and the extent of dilution;and AUand ASare the absorbances of theTest solution and theStandard solution,respectively.

(LC/D)(RU/RS),