Identification—
Add a portion of powdered Tablets,equivalent to about 50mg of oxybutynin chloride,to 10mLof chloroform.Mix for two minutes,and centrifuge.The supernatant layer of the solution so obtained responds to the
Thin-Layer Chromatographic Identification Test á201ñ,methanol being used as the developing solvent and iodine vapor being used to visualize the spots.
Dissolution á711ñ—
Medium:
water;900mL.
Apparatus 2:
50rpm.
Time:
30minutes.
Procedure—
Determine the amount of C
22H
31NO
3·HCl dissolved using the method set forth in the
Assay,making any necessary modifications to the concentration of the
Standard preparationto correspond to that of the solution under test.
Tolerances—
Not less than 80%(Q)of the labeled amount of C22H31NO3·HCl is dissolved in 30minutes.
Assay—
Solvent A—
Add about 0.9mLof triethylamine to a filtered and deaerated mixture of water and methanol (3200:800).Adjust with phosphoric acid to a pHof 3.5±0.05.
Mobile phase—
Prepare a degassed and filtered mixture of Solvent Aand acetonitrile (80:20).
Standard preparation—
Prepare a solution of
USP Oxybutynin Chloride RSin
Mobile phasehaving an accurately known concentration of about 0.05mg per mL.
Assay preparation—
Weigh and finely powder not less than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 50mg of oxybutynin chloride,to a 1000-mLvolumetric flask,add about 400mLof Mobile phase,sonicate for about 10minutes,shake by mechanical means for about 45minutes,dilute with Mobile phaseto volume,and mix.
Chromatographic system—
The liquid chromatograph is equipped with a 203-nm detector,and a 4-mm ×30-cm column that contains packing L10.The flow rate is about 2mLper minute.Chromatograph the Standard preparation,and record the chromatogram 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 major peaks.Calculate the quantity,in mg,of C
22H
31NO
3·HCl in the portion of Tablets taken by the formula:
1000C(rU/rS),
in which
Cis the concentration,in mg per mL,of
USP Oxybutynin Chloride RSin the
Standard preparation,and
rUand
rSare the oxybutynin peak responses obtained from the
Assay preparationand the
Standard preparation,respectively.