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» Metronidazole Benzoate contains not less than 98.5 percent and not more than 101.0 percent of C13H13N3O4, calculated on the dried basis.
Packaging and storage Preserve in well-closed, light-resistant containers. Store at 25, excursions permitted between 15 and 30.
USP Reference standards 11
B: The principal spot in the chromatogram of the Test solution corresponds to that in the chromatogram of Standard solution A, as obtained in the test for Related compounds.
Acidity Neutralize 40 mL of a mixture of dimethylformamide and water (1:1) with hydrochloric acid or 0.02 M sodium hydroxide, add 0.2 mL of methyl red TS and 2.0 g of Metronidazole Benzoate, mix to dissolve, and titrate with 0.02 M sodium hydroxide: not more than 0.25 mL is required to produce a color change.
Loss on drying 731 Dry it at 80 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%.
Adsorbent: 0.2-mm layer of chromatographic silica gel mixture.
Test solution Transfer about 200 mg of Metronidazole Benzoate, accurately weighed, to a 10-mL volumetric flask, dissolve in and dilute with acetone to volume, and mix.
Standard solution A Dissolve an accurately weighed quantity of USP Metronidazole Benzoate RS in acetone, and dilute quantitatively, and stepwise if necessary, with acetone to obtain a solution having a known concentration of about 0.1 mg per mL.
Standard solution B Transfer 4.0 mL of Standard solution A to a 10-mL volumetric flask, dilute with acetone to volume, and mix.
Standard solution C Transfer about 10 mg each of USP Metronidazole RS and USP Tinidazole Related Compound A RS, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with acetone to volume, and mix. [noteUSP Tinidazole Related Compound A RS is 2-methyl-5-nitroimidazole. ]
Application volume: 10 µL.
Developing solvent system: ethyl acetate.
Procedure Proceed as directed for Thin-Layer Chromatography under Chromatography 621. Examine the plate under short-wavelength UV light: the test is valid only if the metronidazole and tinidazole related compound A spots obtained from Standard solution C are clearly separated: no secondary spot obtained from the Test solution is larger or more intense than the principal spot obtained from Standard solution A (0.5%); and not more than three spots, excluding the principal spot, obtained from the Test solution are larger or more intense than the principal spot obtained from Standard solution B (0.2%).
Assay Transfer about 250 mg of Metronidazole Benzoate, accurately weighed, to a suitable container, and dissolve with stirring in 50.0 mL of glacial acetic acid. Titrate with 0.1 N perchloric acid, determining the endpoint potentiometrically. Perform a blank determination, and make any necessary correction (see Titrimetry 541). Each mL of 0.1 N perchloric acid is equivalent to 27.53 mg of C13H13N3O4.
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USP35NF30 Page 3906Pharmacopeial Forum: Volume No. 31(3) Page 781