Medium:pH7.4phosphate buffer (see Buffer Solutionsin the section Reagents,Indicators,and Solutions);900mL.

Apparatus 2: 75rpm.

Time: 30minutes.

Procedure— Measure the amount in solution in filtered portions of the Dissolution Medium,suitably diluted with water,if necessary,at the wavelength of maximum absorbance at about 226nm,with a suitable spectrophotometer,in comparison with a solution having a known concentration of USP Tolbutamide RS.An amount of alcohol not to exceed 1%of the total volume of the Standard solution may be used to bring the Reference Standard into solution prior to dilution with Dissolution Medium.

Tolerances— Not less than 70%(Q)of the labeled amount of C12H18N2O3Sis dissolved in 30minutes.

Mobile phase ,Internal standard solution,Standard preparation,and Chromatographic system—Prepare as directed in the Assayunder Tolbutamide.

Assay preparation— Weigh and finely powder not less than 10Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 150mg of tolbutamide,to a suitable container.Add 100.0mLof Internal standard solutionand about 20glass beads.Securely close the container,and shake vigorously by mechanical means for approximately 30minutes.Centrifuge and use the clear supernatant.

Procedure— Proceed as directed for Procedurein the Assayunder Tolbutamide.Calculate the quantity,in mg,of C12H18N2O3Sin the portion of Tablets taken by the formula: in which the terms are as defined therein.