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C4H6N2S 114.17

2H-Imidazole-2-thione, 1,3-dihydro-1-methyl-.
1-Methylimidazole-2-thiol [60-56-0].
» Methimazole contains not less than 98.0 percent and not more than 101.0 percent of C4H6N2S, calculated on the dried basis.
Packaging and storage— Preserve in well-closed, light-resistant containers.
B: Mercuric chloride TS produces in a solution (1 in 200) a white precipitate, but no precipitation is produced by trinitrophenol TS. The solution is colored intensely blue by molybdophosphotungstate TS.
Melting range 741: between 143 and 146.
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%.
Selenium 291: 0.003%, a 200-mg specimen being used.
Ordinary impurities 466
Test solution: ethyl acetate.
Standard solution: ethyl acetate.
Eluant: a mixture of toluene, isopropyl alcohol, and ammonium hydroxide (70:29:1), in a nonequilibrated chamber.
Visualization: 2.
Assay— Dissolve about 250 mg of Methimazole, accurately weighed, in 75 mL of water. Add from a buret 15 mL of 0.1 N sodium hydroxide VS, mix, and add, with agitation, about 30 mL of 0.1 N silver nitrate. Add 1 mL of bromothymol blue TS, and continue the titration with the 0.1 N sodium hydroxide VS until a permanent, blue-green color is produced. Each mL of 0.1 N sodium hydroxide is equivalent to 11.42 mg of C4H6N2S.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Elena Gonikberg, Ph.D.
Senior Scientist
(MDGRE05) Monograph Development-Gastrointestinal Renal and Endocrine
Reference Standards Lili Wang, Technical Services Scientist
USP32–NF27 Page 2924
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.