Dissolution 
711
—
Medium:
pH 7.6 phosphate buffer (see
pH 791); 900 mL.
Apparatus 1:
100 rpm.
Time:
60 minutes.
Procedure—
Determine the amount of C
15H
20N
2O
4S dissolved from UV absorbances at the wavelength of maximum absorbance at about 245 nm of filtered portions of the solution under test, suitably diluted with
Medium, if necessary, using
Medium as the blank, in comparison with a Standard solution having a known concentration of
USP Acetohexamide RS in the same
Medium.
Tolerances—
Not less than 75% (Q) of the labeled amount of C15H20N2O4S is dissolved in 60 minutes.
Assay—
Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 500 mg of acetohexamide, to a 100-mL volumetric flask, add 60 mL of 0.1 N sodium hydroxide, and shake for 30 minutes. Dilute with water to volume, mix, and filter, discarding the first 20 mL of the filtrate. Transfer 20.0 mL of the subsequent filtrate to a 125-mL separator, add 2 mL of 3 N hydrochloric acid, and extract with four 40-mL portions of chloroform, filtering each portion through chloroform-washed paper into a 200-mL volumetric flask. Dilute with chloroform to volume, and mix. Transfer 20.0 mL of this solution to a suitable beaker, and evaporate on a steam bath to dryness. Transfer the residue, with the aid of 0.1 N sodium hydroxide, to a 100-mL volumetric flask, add 0.1 N sodium hydroxide to volume, and mix. Transfer 10.0 mL of this solution to a third 100-mL volumetric flask, dilute with water to volume, and mix. Concomitantly determine the absorbances of the solution from the Tablets and a Standard solution prepared from
USP Acetohexamide RS, in the same medium, at a concentration of about 10 µg per mL, in 1-cm cells, at the wavelength of maximum absorbance at about 247 nm, with a suitable spectrophotometer, using 0.01 N sodium hydroxide as the blank. Calculate the quantity, in mg, of C
15H
20N
2O
4S in the portion of Tablets taken by the formula:
50C(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Acetohexamide RS in the Standard solution; and
AU and
AS are the absorbances of the solution from the Tablets and the Standard solution, respectively.
