(en sul' i zole).
2-Phenylbenzimidazole-5-sulfonic acid [27503-81-7].
Ensulizole contains NLT 98.0% and NMT 102.0% of C13H10N2O3S, calculated on the dried basis.
• B. Ultraviolet Absorption 197U
Sample solution: 5 µg/mL
[NoteTransfer 100 mg of Ensulizole to a 100-mL volumetric flask, dissolve in 4 mL of 1 N sodium hydroxide, and dilute with water to volume. Transfer 0.5 mL of the solution to a 100-mL volumetric flask, and dilute with water to volume. ]
Acceptance criteria: The absorptivities, calculated on the dried basis, at the wavelength of maximum absorbance at about 302 nm, do not differ by more than 3.0%.
Sample solution: 48 mg/mL of Ensulizole in 0.5 N sodium hydroxide
Titrant: 0.5 N hydrochloric acid VS
Analysis: To the Sample solution, add phenolphthalein TS, and titrate the excess with Titrant. Perform a blank determination, and make any necessary corrections (see Titrimetry 541). Each mL of 0.5 N sodium hydroxide is equivalent to 137.15 mg of C13H10N2O3S.
Calculate the percentage of C13H10N2O3S in the portion of Ensulizole taken:
Result = [(N × (VB VA))/(W × (1 LOD))] × Mr1 × 100
Acceptance criteria: 98.0%102.0% on the dried basis
• Loss on Drying 731: Dry a sample at 105 for 4 h: it loses NMT 2.0% of its weight.
• Packaging and Storage: Preserve in tight containers in a cool place.
• USP Reference Standards 11
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USP35NF30 Page 3046Pharmacopeial Forum: Volume No. 35(4) Page 849