(sul'' fa meth' i zole).
» Sulfamethizole contains not less than 98.0 percent and not more than 101.0 percent of C9H10N4O2S2, calculated on the dried basis.
Packaging and storage Preserve in well-closed, light-resistant containers.
USP Reference standards 11
Clarity and color of solution Dissolve 1.0 g in 20 mL of water and 5 mL of 1 N sodium hydroxide: the solution is clear and not more than pale yellow.
B: To about 0.1 g add 5 mL of 3 N hydrochloric acid, and boil gently for about 5 minutes. Cool in an ice bath, then add 4 mL of a sodium nitrite solution (1 in 100), add water to make 10 mL, and place the mixture in an ice bath for 10 minutes. To 5 mL of the cooled mixture add a solution of 50 mg of 2-naphthol in 2 mL of sodium hydroxide solution (1 in 10): an orange-red precipitate is formed, and it darkens on standing.
C: To about 20 mg suspended in 5 mL of water add, dropwise, 1 N sodium hydroxide until dissolved, then add 2 or 3 drops of cupric sulfate TS: a light green precipitate is formed, and it does not change on standing.
D: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that of the Standard preparation as obtained in the Assay.
Melting range 741: between 208 and 212.
Acidity Digest 2.0 g with 100 mL of water at about 70 for 5 minutes, cool immediately to about 20, and filter. To 25.0 mL of the filtrate add 2 drops of phenolphthalein TS, and titrate with 0.10 N sodium hydroxide: not more than 0.50 mL is required for neutralization. Save the remainder of the filtrate for the tests for Chloride and for Sulfate.
Loss on drying 731 Dry it at 105 for 2 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281: not more than 0.1%.
Chloride 221 A 25.0-mL portion of the filtrate prepared in the test for Acidity shows no more chloride than corresponds to 0.10 mL of 0.020 N hydrochloric acid (0.014%).
Sulfate 221 A 25.0-mL portion of the filtrate prepared in the test for Acidity shows no more sulfate than corresponds to 0.20 mL of 0.020 N sulfuric acid (0.04%).
Selenium 291: 0.003%.
Heavy metals, Method II 231: 0.002%.
Ordinary impurities 466
Test solution: methanol.
Standard solution: methanol.
Mobile phase Prepare a filtered and degassed mixture of water, methanol, and glacial acetic acid (69:30:1). Make adjustments if necessary (see System Suitability under Chromatography 621).
Standard preparation Dissolve an accurately weighed quantity of USP Sulfamethizole RS in methanol to obtain a solution having a known concentration of about 0.4 mg per mL. Quantitatively dilute a volume of this solution with Mobile phase to obtain the Standard preparation having a known concentration of about 8 µg per mL.
Assay preparation Transfer about 20 mg of sulfamethizole, accurately weighed, to a 50-mL volumetric flask, dilute with methanol to volume, and mix. Quantitatively dilute a volume of this solution with Mobile phase to obtain the Assay preparation having a concentration of about 8 µg per mL.
Chromatographic system (see Chromatography 621)The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm × 30-cm column that contains 10-µm packing L1. The flow rate is about 1.0 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the column efficiency determined from the analyte peak is not less than 2000 theoretical plates, the tailing factor for the analyte peak is not more than 2.0, and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure Separately inject equal volumes (about 50 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 C9H10N4O2S2 in the portion of Sulfamethizole taken by the formula:
2.5C(rU / rS)in which C is the concentration, in µg per mL, of USP Sulfamethizole RS in the Standard preparation, and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.
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