Identification—
The visible absorption spectrum of the solution from the
Assay preparation, prepared as directed in the
Assay, exhibits maxima and minima at the same wavelengths as that of the
Standard preparation, prepared as directed in the
Assay and concomitantly measured.
Dissolution 
711
—
Medium:
pH 7.5 phosphate buffer (see under Buffer Solutions in the section Reagents, Indicators, and Solutions); 900 mL.
Apparatus 1:
100 rpm.
Time:
60 minutes.
Procedure—
Determine the amount of C
18H
14N
4O
5S dissolved from UV absorbances at the wavelength of maximum absorbance at about 358 nm of filtered portions of the solution under test, suitably diluted with
Dissolution Medium, if necessary, in comparison with a Standard solution having a known concentration of
USP Sulfasalazine RS in the same
Medium.
Tolerances—
Not less than 85% (Q) of the labeled amount of C18H14N4O5S is dissolved in 60 minutes.
Assay—
Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 150 mg of sulfasalazine, to a 100-mL volumetric flask, add 50 mL of 0.1 N sodium hydroxide, and mix. Dilute with 0.1 N sodium hydroxide to volume, mix, and filter, discarding the first 20 mL of the filtrate. Transfer 5.0 mL of the filtrate to a 1000-mL volumetric flask containing about 750 mL of water, mix, add 20.0 mL of 0.1 N acetic acid, mix, dilute with water to volume, and mix. Concomitantly determine the absorbances of this solution and of a Standard solution of
USP Sulfasalazine RS in the same medium having a known concentration of about 7.5 µg per mL, at the wavelength of maximum absorbance at about 359 nm, using water as the blank. Calculate the quantity, in mg, of sulfasalazine (C
18H
14N
4O
5S) in the portion of Tablets taken by the formula:
20C(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Sulfasalazine RS in the Standard solution; and
AU and
AS are the absorbances of the solution from the Tablets and the Standard solution, respectively.
