(sul'' fa kwin ox' a leen).
» Sulfaquinoxaline contains not less than 98.0 percent and not more than 101.0 percent of C14H12N4O2S, calculated on the dried basis.
Packaging and storage Preserve in well-closed containers, protected from light.
Labeling Label it to indicate that it is for veterinary use only.
USP Reference standards 11
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.
Loss on drying 731 Dry it at 105 for 4 hours: it loses not more than 1.0% of its weight.
Residue on ignition 281: not more than 0.1%.
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%).
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 C14H12N4O2S 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.
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USP35NF30 Page 4720Pharmacopeial Forum: Volume No. 37(4)