A: Infrared Absorption á197Kñ.

B: Ultraviolet Absorption á197Uñ—

Solution A: water.

Solution B— Prepare a filtered and degassed mixture of acetonitrile,water,and triethylamine (160:40:1).Adjust with phosphoric acid to a pHof 7.0.

Diluent— Prepare a mixture of Solution Aand Solution B(9:1).

Blank solution— Prepare a mixture of Diluentand methanol (9:1).

Mobile phase— Use variable mixtures of Solution Aand Solution Bas directed for Chromatographic system.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Resolution solution— [NOTE—Prepare immediately before using.]Dissolve 5mg each of USP Lansoprazole RSand USP Lansoprazole Related Compound A RSin 200mLof methanol.Pipet 1mLof this solution into a 10-mLvolumetric flask,dilute with Diluentto volume,and mix.

System suitability solution— Dissolve a suitable quantity of USP Lansoprazole Related Compound A RSin methanol,and dilute quantitatively,and stepwise if necessary,to obtain a solution having a known concentration of about 0.025mg per mL.Pipet 1mLof this solution into a 10-mLvolumetric flask,dilute with Diluentto volume,and mix.

Standard solution— Dissolve an accurately weighed quantity of USP Lansoprazole RSin methanol,and dilute quantitatively,and stepwise if necessary,with methanol to obtain a solution having a known concentration of about 25µg per mL.Pipet 1mLof this solution into a 10-mLvolumetric flask,dilute with Diluentto volume,and mix.

Test solution— [NOTE—Prepare immediately before using.]Transfer about 125mg of Lansoprazole,accurately weighed,to a 50-mLvolumetric flask,dissolve in and dilute with methanol to volume,and mix.Pipet 1mLof this solution into a 10-mLvolumetric flask,and dilute with Diluentto volume.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 285-nm detector and a 4.6-mm ×15-cm column that contains 5-µm packing L1.The flow rate is about 0.8mLper minute.The chromatograph is programmed as follows. Chromatograph the Resolution solution,and record the peak responses as directed for Procedure:the resolution,R,between lansoprazole and lansoprazole related compound Ais not less than 6.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the relative standard deviation for replicate injections is not more than 3%.

Procedure— Separately inject equal volumes (about 40µL)of the Blank solution,the Standard solution,and the Test solutioninto the chromatograph,record the chromatograms,and measure the areas for the major peaks,excluding the peaks obtained from the Blank solution.Calculate the percentage of each impurity in the portion of Lansoprazole taken by the formula: in which Cis the concentration,in µg per mL,of USP Lansoprazole RSin the Standard solution;Wis the weight,in mg,of Lansoprazole taken for the Test solution;riis the peak response for each impurity obtained from the Test solution;and rSis the peak response for lansoprazole obtained from the Standard solution:not more than 1.0%of total impurities is found.

Diluent— Prepare a mixture of water,acetonitrile,and triethylamine (60:40:1),and adjust with phosphoric acid to a pHof 10.0.

Mobile phase— Prepare a filtered and degassed mixture of water,acetonitrile,and triethylamine (60:40:1).Adjust with phosphoric acid to a pHof 7.0.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Resolution solution— Dissolve suitable quantities of USP Lansoprazole RSand USP Lansoprazole Related Compound A RSin Diluentto obtain a solution containing about 0.1mg of each per mL.

Internal standard solution— Dissolve an accurately weighed quantity of 4¢-ethoxyacetophenone in Diluentto obtain a solution having a known concentration of about 2.5mg per mL.

Standard preparation— Dissolve an accurately weighed quantity of USP Lansoprazole RSin Internal standard solutionto obtain a solution having a known concentration of about 5.0mg per mL.Transfer 1.0mLof this solution to a 50-mLvolumetric flask,dilute with Diluentto volume,and mix.

Assay preparation— Transfer about 50mg of Lansoprazole,accurately weighed,to a 10-mLvolumetric flask,dissolve in and dilute with Internal standard solutionto volume,and mix.Transfer 1.0mLof this solution to a 50-mLvolumetric flask,dilute with Diluentto volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 285-nm detector and a 4.6-mm ×25-cm column that contains 5-µm packing L1.The flow rate is about 1mLper minute.Chromatograph the Resolution solution,and record the peak responses as directed forProcedure:the resolution,R,between lansoprazole and lansoprazole related compound Ais not less than 5.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative standard deviation for replicate injections is not more than 0.5%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the peak responses.Calculate the quantity,in mg,of C16H14F3N3O2Sin the portion of Lansoprazole taken by the formula: in which Cis the concentration,in mg per mL,of USP Lansoprazole RSin the Standard preparation;and RUand RSare the peak response ratios obtained from the Assay preparationand the Standard preparation,respectively.