Packaging and storage—
Preserve in tight, light-resistant containers.
Identification—
B:
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 solution from the
Standard preparation, prepared as directed in the
Assay, concomitantly measured.
Chloride 
221
—
Digest 2.0 g of Sulfasalazine with 100 mL of water at 70
for 5 minutes. Cool immediately to room temperature, and filter. Transfer a 25-mL portion of the filtrate to a 50-mL beaker (retain the remainder of this filtrate for the
Sulfate test), add 1 mL of nitric acid, mix, and allow to stand for 5 minutes. Filter through a fine texture, retentive filter paper (Whatman No. 42, or equivalent): the filtrate shows no more chloride than corresponds to 0.10 mL of 0.020 N hydrochloric acid (0.014%).
Sulfate 221—
Transfer a 25-mL portion of the filtrate from the
Chloride test to a 50-mL beaker. Add 1 mL of 3 N hydrochloric acid, mix, and allow to stand for 5 minutes. Filter through a fine texture, retentive filter paper (Whatman No. 42, or equivalent): the filtrate shows no more sulfate than corresponds to 0.20 mL of 0.020 N sulfuric acid (0.04%).
Heavy metals, Method II 231:
0.002%.
Chromatographic purity—
Prepare a solution of Sulfasalazine in a mixture of alcohol and 2
M ammonium hydroxide (4:1) having a concentration of 10 mg per mL. Similarly prepare a Standard solution of
USP Sulfasalazine RS in the same medium having a concentration of 10 mg per mL. Dilute aliquots of the Standard solution quantitatively and stepwise with the same medium to obtain solutions having concentrations of 200, 150, 100, and 20 µg per mL, corresponding to 2.0%, 1.5%, 1.0%, and 0.2%, respectively (
Standard dilutions A,
B,
C, and
D). Separately apply 10-µL each of the test solution, the Standard solution, and the
Standard dilutions to a suitable thin-layer chromatographic plate (see
Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture. Allow the spots to dry, and develop the chromatogram in an unequilibrated chamber with a solvent system consisting of a mixture of chloroform, acetone, and formic acid (60:30:5) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the chamber, mark the solvent front, dry with the aid of a current of hot air, and examine the plate under short-wavelength UV light: the
RF value of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution, and no spots, other than the principal spot, in the chromatogram of the test solution are larger or more intense than the principal spot obtained from
Standard dilution A (2%), and the sum of the intensities of any secondary spots detected does not exceed 4%.
Organic volatile impurities, Method V 467:
meets the requirements.
Solvent—
Use dimethyl sulfoxide.
Assay—
Transfer about 150 mg of Sulfasalazine, accurately weighed, to a 100-mL volumetric flask. Dissolve in 0.1 N sodium hydroxide, dilute with 0.1 N sodium hydroxide to volume, and mix. Transfer 5.0 mL of this solution to a 1000-mL volumetric flask containing about 750 mL of water, mix, add 20.0 mL of 0.1 N acetic acid, 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 C
18H
14N
4O
5S in the Sulfasalazine 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 obtained from the assay solution and the Standard solution, respectively.
;)
