A:Infrared Absorption á197Mñ.

B: It meets the requirements of the flame test for Sodium á191ñ.

Borate solution and Diluent— Prepare as directed in the Assay.

Buffer solution— Transfer 5.88g of sodium citrate dihydrate and 2.84g of anhydrous dibasic sodium phosphate to a 2-Lvolumetric flask,dilute with water to volume,and mix.Adjust with phosphoric acid to a pHof 8,and pass the solution through a filter having a 0.5-µm or finer porosity.

9-Fluorenylmethyl chloroformate solution— Prepare a solution in acetonitrile containing about 4mg of 9-fluorenylmethyl chloroformate per mL.Prepare this solution fresh just prior to use.

Solution A— Prepare a filtered and degassed mixture of Buffer solution and acetonitrile (17:3).

Solution B— Prepare a filtered and degassed mixture of acetonitrile and Buffer solution (7:3).

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

Standard stock solution— Prepare a solution of USP Alendronate Sodium RSinDiluent having a known concentration of about 0.6mg per mL.

Standard solution— Transfer 5.0mLof theStandard stock solution to a 50-mLpolypropylene,screw-cap centrifuge tube containing 5mLofBorate solution.Add 5mLof acetonitrile and 5mLof9-Fluorenylmethyl chloroformate solution,and shake for 45seconds.Allow to stand at room temperature for 30minutes.Add 20mLof methylene chloride,and shake vigorously for 1minute.Centrifuge for 5to 10minutes,and use a portion of the clear upper aqueous layer.

Diluted standard solution— Dilute a portion of the Standard stock solutionwithDiluent to obtain a solution having a known concentration of about 0.6µg per mL.Using 5mLof this solution,proceed as directed for the Standard solution,beginning with “to a 50-mLpolypropylene,screw-cap centrifuge tube.”

Reagent blank— Using a 5.0-mLportion ofDiluent,proceed as directed forStandard solution,beginning with “to a 50-mLpolypropylene,screw-cap centrifuge tube.”

Test solution— Transfer about 30mg of Alendronate Sodium,accurately weighed,to a 50-mLvolumetric flask,dissolve in and dilute withDiluent to volume,and mix.Using a 5.0-mLvolume of this solution,proceed as directed forStandard solution,beginning with “to a 50-mLpolypropylene,screw-cap centrifuge tube.”

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 266-nm detector and a 4.1-mm ×25-cm column that contains packing L21.The flow rate is about 1.8mLper minute.The column temperature is maintained at about 45.The chromatograph is programmed as follows. Chromatograph theStandard solution and theDiluted standard solution,and record the peak responses as directed forProcedure:the tailing factor for the main peak in the chromatogram of theStandard solution is not more than 2.0;and the peak at that locus in the chromatogram of theDiluted standard solution is detectable with a signal-to-noise ratio of not less than 3.

Procedure— Separately inject equal volumes (about 20µL)of theTest solution and theReagent blank into the chromatograph,record the chromatograms,and measure the responses for all the peaks.Disregard any peak corresponding to those obtained from the Reagent blank.Calculate the percentage of each impurity in the portion of Alendronate Sodium taken by the formula: in whichriis the area of each impurity peak,andrsis the sum of all impurity peaks and the main peak:not more than 0.1%of any individual impurity is found,and not more than 0.5%of total impurities is found.

Buffer solution— Transfer 14.7g of sodium citrate dihydrate and 7.05g of anhydrous dibasic sodium phosphate to a 1-Lvolumetric flask,dilute with water to volume,mix,and adjust with phosphoric acid to a pHof 8.

Diluent— Dissolve 29.4g of sodium citrate dihydrate in water in a 1-Lvolumetric flask,dilute with water to volume,and mix.

Borate solution— Dissolve 19.1g of sodium borate in water in a 1-Lvolumetric flask,dilute with water to volume,and mix.

9-Fluorenylmethyl chloroformate solution— Prepare a solution in acetonitrile containing about 0.5mg of 9-fluorenylmethyl chloroformate per mL.Prepare this solution fresh just prior to use.

Mobile phase— Prepare a filtered and degassed mixture ofBuffer solution,acetonitrile,and methanol (70:25:5).Make adjustments if necessary (seeSystem Suitability underChromatography á621ñ).

Standard stock preparation— Prepare a solution of USP Alendronate Sodium RSinDiluenthaving a known concentration of about 0.1mg per mL.Calculate the concentration,CS,of anhydrous alendronate sodium in this solution.

Standard preparation— Transfer 5.0mLof the Standard stock preparationto a 50-mLpolypropylene,screw-cap centrifuge tube containing 5mLofBorate solution.Add 5mLof 9-Fluorenylmethyl chloroformate solution,and shake for 30seconds.Allow to stand at room temperature for 25minutes.Add 25mLof methylene chloride,and shake vigorously for 1minute.Centrifuge for 5to 10minutes.Use a portion of the clear upper aqueous layer.

Reagent blank— Using 5.0mLofDiluent,proceed as directed forStandard preparation,beginning with “to a 50-mLpolypropylene,screw-cap centrifuge tube.”

Assay stock preparation— Transfer about 25mg of Alendronate Sodium,accurately weighed,to a 250-mLvolumetric flask,dissolve in and dilute with Diluentto volume,and mix.

Assay preparation— Using 5.0mLof the Assay stock preparation,proceed as directed for the Standard preparation,beginning with “to a 50-mLpolypropylene,screw-cap centrifuge tube.”

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 266-nm detector and a 4.1-mm ×25-cm column that contains packing L21.The flow rate is about 1.2mLper minute.The column temperature is maintained at about 35.Chromatograph theStandard preparation,and record the peak responses as directed forProcedure:the column efficiency is not less than 1500theoretical 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)of theStandard preparation,the Assay preparation,and the Reagent blankinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C4H12NNaO7P2in the portion of Alendronate Sodium taken by the formula: in which Dis the dilution factor for the Assay stock preparation;CSis as defined under theStandard stock preparation;andrUandrSare the peak area responses for alendronic acid obtained from theAssay preparation and theStandard preparation,respectively.USP28