Solution— Transfer a volume of Oral Solution,equivalent to about 20mg of fluoxetine,to a separatory funnel,add 5.0mLof water and 0.5mLof 1Nsodium hydroxide,extract with 5mLof chloroform,and discard the aqueous layer.Evaporate the remaining layer to dryness,and dissolve the residue in 0.4mLof chloroform.

FOR ORAL SOLUTION PACKAGED IN SINGLE-UNIT CONTAINERS: meets the requirements.

FOR ORAL SOLUTION PACKAGED IN MULTIPLE-UNIT CONTAINERS: meets the requirements.

Ion-pair solution— Transfer about 4.3g of sodium 1-octanesulfonate and 13.8g of monobasic sodium phosphate to a suitable container,dissolve in 1Lof water,and adjust with phosphoric acid to a pHof 3.0.

Diluent— Prepare a mixture of Ion-pair solution,methanol,and acetonitrile (6:3:1).

Solution A— Prepare a filtered and degassed mixture of Ion-pair solution,methanol,and acetonitrile (53:26:21).

Solution B— Prepare a filtered and degassed mixture of Ion-pair solution,acetonitrile,and methanol (43:35:22).

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

System suitability solution— Dissolve a quantity of USP Fluoxetine Hydrochloride RSin 1Nsulfuric acid to obtain a solution having a known concentration of about 2.0mg per mL,and heat at 85for 1hour.Transfer 1.0mLof this solution to a 100-mLvolumetric flask,add about 10mg of USP Fluoxetine Hydrochloride RS,dissolve in and dilute with Diluentto volume,and mix.

Test solution— Transfer an accurately measured volume of Oral Solution,equivalent to about 19mg of fluoxetine,to a 10-mLvolumetric flask,dilute with Diluentto volume,and mix.

Diluted test solution— Transfer 1.0mLof the Test solutionto a 25-mLvolumetric flask,dilute with Diluentto volume,and mix.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 215-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 1mLper minute.The chromatograph is programmed as follows. Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the retention time of any peak,except the peak for fluoxetine,is less than 13minutes.

Procedure— Separately inject equal volumes (about 20µL)of the Diluted test solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure all of the peak responses.Calculate the percentage of each impurity in the volume of Oral Solution taken by the formula: in which riis the peak response for each impurity obtained from the Test solution;and rSis the peak response for fluoxetine obtained from the Diluted test solution:not more than 0.4%of any individual impurity is found;and not more than 0.8%of total impurities is found.

Triethylamine buffer— Transfer about 10mLof triethylamine,accurately measured,to a suitable container,add about 980mLof water,and adjust with phosphoric acid to a pHof 6.0.

Mobile phase— Prepare a filtered and degassed mixture of Triethylamine bufferand acetonitrile (1:1).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Fluoxetine Hydrochloride RSin Mobile phase,and dilute quantitatively,and stepwise if necessary,with Mobile phaseto obtain a solution having a known concentration of about 45µg per mL.

Assay preparation— Transfer an accurately measured volume of Oral Solution,equivalent to about 4.0mg of fluoxetine,to a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 215-nm detector and a 4.6-mm ×25-cm column that contains packing L10.The flow rate is about 1mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure: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 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the fluoxetine peak.Calculate the quantity,in mg,of fluoxetine (C17H18F3NO)in the volume of Oral Solution taken by the formula: in which 309.33and 345.79are the molecular weights for fluoxetine and fluoxetine hydrochloride,respectively;Cis the concentration,in µg per mL,of USP Fluoxetine Hydrochloride RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.