Packaging and storage—
Preserve in well-closed containers, protected from light.
Labeling—
Label it to indicate that it is for veterinary use only.
Identification—
Solution:
10 µg per mL.
Medium:
0.01 N sodium hydroxide.
C:
Dissolve 4 mg in 2 mL of 2 N hydrochloric acid, add 0.2 mL of sodium nitrite solution (1 in 100), and allow to stand for 2 minutes. Add the solution to 1 mL of 2-naphthol TS: an orange-red precipitate is formed.
Acidity—
Digest 2 g of it with 100 mL of water at about 70
for 5 minutes, cool to about 20
, and filter. Titrate 50 mL of the filtrate with 0.1 N sodium hydroxide VS to a pH of 7.0: not more than 0.2 mL is required.
Heavy metals, Method II 
231
:
0.002%.
Related compounds—
Dissolve 400 mg of Sulfaquinoxaline in 4 mL of 1 N sodium hydroxide, add methanol to obtain 100 mL of solution, and mix (test solution). Prepare a solution of
USP Sulfaquinoxaline Related Compound A RS in methanol containing 0.12 mg per mL (
Standard solution 1). Prepare a solution of sulfanilamide in methanol containing 0.04 mg per mL (
Standard solution 2). Separately apply 5 µL each of the test solution,
Standard solution 1, and
Standard solution 2 to a 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 a solvent system consisting of a mixture of chloroform, methanol, and ammonium hydroxide (60:40:20) 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, allow it to air-dry, and examine the plate under short-wavelength UV light: no spot corresponding to sulfaquinoxaline related compound A in the chromatogram obtained from the test solution is more intense than the principal spot in the chromatogram obtained from
Standard solution 1 (3.0%), and no spot, other than the principal spot and the sulfaquinoxaline related compound A spot, if any, in the chromatogram obtained from the test solution is more intense than the principal spot in the chromatogram obtained from
Standard solution 2 (1.0%).
Assay—
Mobile phase—
Dissolve 2 g of monobasic ammonium phosphate in 1000 mL of a mixture of water, acetonitrile, glacial acetic acid, tetrahydrofuran, and ammonium hydroxide (583:400:10:5:2). Filter through a filter of 0.5 µm or finer porosity, and degas. Make adjustments if necessary (see
System suitability under
Chromatography 621).
Standard preparation—
Dissolve an accurately weighed quantity of
USP Sulfaquinoxaline RS in 0.01 N sodium hydroxide to obtain a solution having a known concentration of about 0.7 mg per mL.
Assay preparation—
Transfer about 175 mg of Sulfaquinoxaline, accurately weighed, to a 250-mL volumetric flask, dilute with 0.01 N sodium hydroxide to volume, and mix.
Chromatographic system
(see
Chromatography 621)—The liquid chromatograph is equipped with a 254-nm detector and a 4-mm × 25-cm column that contains packing L1. The flow rate is about 1 mL per minute. Chromatograph the
Standard preparation, and record the peak responses as directed for
Procedure: the column efficiency is not less than 2500 theoretical plates, the tailing factor is not more than 1.2, and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure—
Separately inject equal volumes (about 15 µL) of the
Standard preparation and the
Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C
14H
12N
4O
2S in the portion of Sulfaquinoxaline taken by the formula:
250C(rU / rS),
in which
C is the concentration, in µg per mL, of
USP Sulfaquinoxaline RS in the
Standard preparation, and
rU and
rS are the sulfaquinoxaline peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
;)
