A: Macerate a portion of powdered Tablets,equivalent to about 300mg of bisacodyl,with 100mLof acetone.Heat on a steam bath to boiling,filter,and evaporate to about 20mL.Add 200mLof water,and warm the mixture on the steam bath,passing a stream of nitrogen over the surface to evaporate the acetone.After 30minutes,cool the mixture,and filter through a sintered-glass funnel.Discard the filtrate,and dissolve the crystals in 50mLof acetone.Evaporate the solution to about 15mL,add about 75mLof water,heat on a steam bath for 15minutes,and then cool.Scratch the sides of the beaker to induce crystallization,filter the crystals,and dry at 100for about 15minutes:the bisacodyl so obtained responds to Identificationtest Aunder Bisacodyl.

B: The retention time of the major peak for bisacodyl in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

Mobile phase ,Standard preparation,and Chromatographic system—Proceed as directed in the Assayunder Bisacodyl Suppositories.

Assay preparation— Transfer an accurately weighed portion of finely powdered Tablets,equivalent to 100mg of bisacodyl,to a 200-mLvolumetric flask,add 25mLof water,and shake by mechanical means for 15minutes followed by sonication for 15minutes.Add 100mLof acetonitrile,and shake by mechanical means for 15minutes followed by sonication for 15minutes.Dilute with acetonitrile to volume,mix,and filter.

Procedure— Separately inject equal volumes (about 10µL)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 C22H19NO4in the Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Bisacodyl RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.