Assay—
[NOTE—Perform this procedure on at least 3individual Capsules.The mean of the assay values obtained is the assay value.
]Transfer 1Capsule to a round,narrow-mouth,screw-capped,120-mLbottle,add about 20mLof 6Nhydrochloric acid,and allow to stand,with frequent swirling,until the Capsule has dissolved.Add 10.0mLof toluene,accurately measured,for each 25mg of the labeled amount of simethicone in the Capsule,close the bottle securely with a cap having an inert liner,and shake by mechanical means for 5minutes.Allow the phases to separate,draw off 10mLof the upper organic (toluene)layer to a test tube containing 0.5g of anhydrous sodium sulfate,agitate vigorously for 30seconds,and allow the mixture to settle.If necessary,centrifuge the mixture to obtain a clear solution (
Assay preparation).Prepare a
Standard preparationby similarly treating a solution of
USP Polydimethylsiloxane RSin toluene having a known concentration of about 2.5mg per mL.Prepare a procedural blank by similarly treating 10.0mLof toluene.Concomitantly determine the absorbances of the solutions in 0.5-mm cells at the wavelength of maximum absorbance at about 7.9µm,with an IRspectrophotometer,using the blank to set the instrument.Calculate the quantity,in mg,of [-(CH
3)
2SiO-]
nin the Capsule taken by the formula:
VC(AU/AS),
in which
Vis the volume,in mL,of toluene taken to prepare the
Assay preparation,
Cis the concentration,in mg per mL,of
USP Polydimethylsiloxane RSin the Standard solution,and
AUand
ASare the absorbances of the
Assay preparationand the
Standard preparation,respectively.