» Sulfamethazine Granulated contains Sulfamethazine mixed with suitable diluents, carriers, and inactive ingredients. It contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of sulfamethazine (C12H14N4O2S).
Packaging and storage Preserve in well-closed containers. Avoid moisture and excessive heat.
Labeling Label it to indicate that it is for veterinary use only. Label it also to indicate that it is for manufacturing, processing, or repackaging.
USP Reference standards 11
Identification The chromatogram of the Assay preparation obtained as directed in the Assay exhibits a major peak for sulfamethazine, the retention time of which corresponds to that exhibited in the chromatogram of the Standard preparation obtained as directed in the Assay.
Loss on drying 731 Dry it in vacuum at 60 for 5 hours: it loses not more than 10% of its weight.
Powder fineness 811: not less than 95% passes a No. 20 sieve, and not more than 10% passes a No. 80 sieve.
Mobile phase Prepare a mixture of water, methanol, and glacial acetic acid (68:30:2). Make adjustments if necessary (see System Suitability under Chromatography 621).
Extractant Prepare a mixture of 0.15 N hydrochloric acid and methanol (3:1).
Standard preparation Prepare a solution of USP Sulfamethazine RS in Extractant having a known concentration of about 0.01 mg per mL.
Assay preparation Transfer about 5 g of Sulfamethazine Granulated, accurately weighed, to a suitable container, add 250.0 mL of Extractant, and shake by mechanical means for 2 hours. Allow the mixture to settle, storing the mixture in a refrigerator if settling is allowed to continue overnight. Filter a portion of the supernatant, and transfer 10.0 mL of the clear filtrate to a 100-mL volumetric flask. Dilute with Extractant to volume, and mix. Transfer 5.0 mL of this solution to a 200-mL volumetric flask, dilute with Extractant to volume, and mix. Pass a portion of this solution through a filter having a 0.5-µm or finer porosity, and use the filtrate as the Assay preparation. This solution contains about 0.01 mg of sulfamethazine per mL.
Derivatizing reagent Dissolve 6.0 g of dimethylaminobenzaldehyde in 200 mL of glacial acetic acid, add 120 mL of methanol and 80 mL of water, mix, and degas. Prepare this reagent daily.
Chromatographic system The liquid chromatograph is equipped with a guard column that contains packing L1, a 4.6-mm × 25-cm analytical column that contains 10-µm packing L1, a separate pump to deliver the Derivatizing reagent via a T-junction installed immediately postcolumn, a postcolumn derivatization coil consisting of 3-m × 0.5-mm inside-diameter polytef tubing, a flow cell, and a 450-nm detector. The Mobile phase flow rate is about 2 mL per minute, and the Derivatizing reagent flow rate is about 1 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the capacity factor, k¢, for the sulfamethazine peak is not less than 2.0; and the relative standard deviation for replicate injections is not more than 3.5%.
Procedure Separately inject equal volumes (about 100 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the sulfamethazine peaks. Calculate the quantity, in mg, of sulfamethazine (C12H14N4O2S) in each g of the Sulfamethazine Granulated taken by the formula:
100,000(C / W)(rU / rS)in which C is the concentration, in mg per mL, of USP Sulfamethazine RS in the Standard preparation; W is the quantity, in g, of Sulfamethazine Granulated taken to prepare the Assay preparation; and rU and rS are the sulfamethazine peak responses obtained from the Assay preparation and the Standard preparation, respectively.
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USP35NF30 Page 4713Pharmacopeial Forum: Volume No. 31(3) Page 797