(sul'' fa dye'' meth ox' een).
» Sulfadimethoxine contains not less than 98.0 percent and not more than 102.0 percent of C12H14N4O4S, calculated on the dried basis.
Packaging and storage Preserve in tight, light-resistant containers, and store at controlled room temperature.
Labeling Label it to indicate that it is for veterinary use only.
USP Reference standards 11
B: Ultraviolet Absorption 197U
Solution: 1 in 100,000.
Absorptivities, calculated on the dried basis, at 272 nm do not differ by more than 3.0%.
C: To about 100 mg, add 3 mL of 2.5 N sodium hydroxide and 50 mL of water, mix until dissolved, and dilute with water to 100 mL. To about 5 mL of this solution, add 100 mg of phenol, and heat to boiling. Cool the solution, and add 0.5 mL of sodium hypochlorite TS and 3 drops of 2.5 N sodium hydroxide: a yellow color is produced.
D: To about 10 mg dissolved in 2 mL of diluted hydrochloric acid, add 3 drops of sodium nitrite solution (1 in 100), and dilute with water to 4 mL: the solution turns yellow. Add 1 mL of 2.5 N sodium hydroxide containing 10 mg of 2-naphthol: a red-orange precipitate is formed.
Melting range 741: between 197 and 202.
Loss on drying 731: Dry it at 105 for 3 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281: not more than 0.1%.
Heavy metals, Method II 231: 0.002%.
Mobile phase Dissolve 6 g of monobasic sodium phosphate in water to make 1000 mL. Adjust with 50% (w/v) sodium hydroxide solution to a pH of 7.0. Prepare a mixture of this solution and methanol (300:100). Make adjustments if necessary (see System Suitability under Chromatography 621).
Standard preparation Quantitatively dissolve an accurately weighed quantity of USP Sulfadimethoxine RS in Mobile phase to obtain a solution having a known concentration of about 0.2 mg per mL. Protect this solution from light.
Assay preparation Transfer about 20 mg of Sulfadimethoxine, accurately weighed, to a 100-mL volumetric flask, add about 75 mL of Mobile phase, and swirl to dissolve. Dilute this solution with Mobile phase to volume, and mix. Protect this solution from light.
Chromatographic system (see Chromatography 621) The liquid chromatograph is equipped with a 254-nm detector and a 4.6-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 tailing factor is not more than 1.5; and the relative standard deviation for replicate injections is not more than 1.0%.
Procedure Separately inject equal volumes (about 10 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 C12H14N4O4S in the portion of Sulfadimethoxine taken by the formula:
100C(rU / rS)in which C is the concentration, in mg per mL, of USP Sulfadimethoxine RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.
Auxiliary Information Please check for your question in the FAQs before contacting USP.
USP35NF30 Page 4710Pharmacopeial Forum: Volume No. 28(6) Page 1871