Foaming solution— Dissolve 500µg of FD&C Blue No.1and 1g of octoxynol 9in 100mLof water.

Procedure— [NOTE—For each test,employ a clean,unused,250-mLglass jar.]Transfer a volume of Oral Suspension,equivalent to 20mg of simethicone,to a clean,unused,cylindrical 250-mLglass jar,fitted with a 50-mm cap,containing 100mLof Foaming solutionthat has been warmed to 37.Proceed as directed for Procedurein the test for Defoaming activityunder Simethicone,beginning with “Cap the jar.”The defoaming activity time does not exceed 45seconds.

Standard preparation— Transfer about 60mg of USP Polydimethylsiloxane RS,accurately weighed,to a 25-mLvolumetric flask,add 15mLof hexanes,and sonicate for 3minutes.Allow to cool,dilute with hexanes to volume,and mix.Transfer 10mLof this solution to a capped test tube,add about 1g of anhydrous sodium sulfate,mix for about 1minute,and centrifuge.Use the clear supernatant as the Standard preparation.The Standard preparationhas a concentration of about 2.4mg of USP Polydimethylsiloxane RSper mL.

Assay preparation— Transfer an accurately measured quantity of Oral Suspension,equivalent to about 240mg of simethicone,to a glass-stoppered centrifuge tube.Add 5mLof methanol,and mix for about 15seconds.Add 30.0mLof hexanes,and mix for about 10seconds.Loosen the stopper,heat the tube for about 10minutes in a water bath at 65±1.Mix for 1minute,and centrifuge.Using a glass syringe,transfer the upper hexanes layer to a 100-mLvolumetric flask.Repeat the extraction with two 30.0-mLportions of hexanes,combining the hexanes extracts in the 100-mLvolumetric flask.[NOTE—If an emulsion forms during any of the extractions,as much as 2mLof methanol may be added to disperse the emulsion.]Allow the combined extracts to cool,dilute with hexanes to volume,and mix.Transfer 10mLof this solution to a capped test tube,add about 1g of anhydrous sodium sulfate,mix for about 1minute,and centrifuge.Use the clear supernatant as the Assay preparation.

Dry hexanes— Mix 100mLof hexanes and 10g of anhydrous sodium sulfate,allow to settle,and centrifuge.Use the clear supernatant.

Procedure— Concomitantly determine the absorbances of the Standard preparationand the Assay preparationat the wavelength of maximum absorption at about 7.9µm,using Dry hexanesas the blank to set the instrument.Calculate the quantity,in mg,of [–(CH3)2SiO–]nin each mLof the Oral Suspension taken by the formula: in which Cis the concentration,in mg per mL,of USP Polydimethylsiloxane RSin the Standard preparation,Vis the volume,in mL,of Oral Suspension taken,and AUand ASare the absorbances of the Assay preparationand the Standard preparation,respectively.