FOR SOLID PACKAGED IN SINGLE-UNIT CONTAINERS: meets the requirements for Content Uniformitywith respect to ampicillin and probenecid.

Standard preparation— Prepare as directed for Standard Preparationunder Iodometric Assay—Antibiotics á425ñ,using USP Ampicillin RS.

Assay preparation— Constitute Ampicillin and Probenecid for Oral Suspension as directed in the labeling,and mix.Transfer the resulting suspension to a high-speed glass blender jar containing sufficient water to make 500.0mL,and blend for about 10minutes.Quantitatively dilute an accurately measured volume of this stock solution with water to obtain an Assay preparationcontaining about 1.25mg of ampicillin per mL.

Procedure— Proceed as directed for Procedureunder Iodometric Assay—Antibiotics á425ñ.Calculate the quantity,in mg,of ampicillin (C16H19N3O4S)in the Ampicillin and Probenecid for Oral Suspension taken by the formula: in which Lis the labeled quantity,in mg,of ampicillin in the Ampicillin and Probenecid for Oral Suspension;and Dis the concentration,in mg per mL,of ampicillin in the Assay preparationon the basis of the labeled quantity in the Ampicillin and Probenecid for Oral Suspension and the extent of dilution.

Standard preparation— Dissolve an accurately weighed portion of USP Probenecid RSin sodium carbonate solution (1in 100)to obtain a solution having a known concentration of about 1mg per mL.

Assay preparation— Constitute Ampicillin and Probenecid for Oral Suspension as directed in the labeling,and mix.Quantitatively dilute the resulting suspension with sodium carbonate solution (1in 100)to obtain a solution containing about 1mg of probenecid per mL,mix,and filter.

Procedure— Transfer 2.0mLof the clear Assay preparationto a 125-mLseparator,and add 8.0mLof 1.0Nhydrochloric acid.Extract this solution with four 20-mLportions of chloroform,filtering each extract through a glass wool pledget and 6g of chloroform-washed anhydrous sodium sulfate into a 100-mLvolumetric flask.Wash the pledget and the sodium sulfate with chloroform,collecting the washings in the 100-mLvolumetric flask,dilute with chloroform to volume,and mix.Treat 2.0mLof the Standard preparationin the same manner.Concomitantly determine the absorbances of the solutions from the Assay preparationand the Standard preparationat the wavelength of maximum absorbance at about 257nm,with a suitable spectrophotometer,using chloroform washed with sodium carbonate solution (1in 100)as the blank.Calculate the quantity,in mg,of probenecid (C13H19NO4S)in the Ampicillin and Probenecid for Oral Suspension taken by the formula: in which Cis the concentration,in mg per mL,of USP Probenecid RSin the Standard preparation;Lis the labeled quantity,in mg,of probenecid in the Ampicillin and Probenecid for Oral Suspension;Dis the concentration,in mg per mL,of probenecid in the Assay preparationon the basis of the labeled quantity in the Ampicillin and Probenecid for Oral Suspension and the extent of dilution;and AUand ASare the absorbances of the solutions from the Assay preparationand the Standard preparation,respectively.