Ensulizole
C13H10N2O3S 274.30
1H-Benzimidazole-5-sulfonic acid-2-phenyl-;
2-Phenylbenzimidazole-5-sulfonic acid
[27503-81-7].
(en sul' i zole).
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C13H10N2O3S 274.30
1H-Benzimidazole-5-sulfonic acid-2-phenyl-;
2-Phenylbenzimidazole-5-sulfonic acid
[27503-81-7].DEFINITION
Ensulizole contains NLT 98.0% and NMT 102.0% of C13H10N2O3S, calculated on the dried basis.
IDENTIFICATION
• B. Ultraviolet Absorption 
197U
197U
Sample solution:
5 µg/mL
[Note—Transfer 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%.
ASSAY
• Procedure
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.
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
VA))/(W × (1 LOD))] × Mr1 × 100| N | = | = actual normality of the Titrant |
| VB | = | = volume of Titrant used for the blank (mL) |
| VA | = | = volume of Titrant used for the Sample solution (mL) |
| W | = | = weight of Ensulizole taken for the Sample solution (mg) |
| LOD | = | = percentage of loss on drying expressed as a decimal fraction, as determined in the test for Loss on Drying |
| Mr1 | = | = molecular weight of ensulizole (274.30) |
Acceptance criteria:
98.0%–102.0% on the dried basis
SPECIFIC TESTS
• Loss on Drying 731:
Dry a sample at 105
for 4 h: it loses NMT 2.0% of its weight.
731:
Dry a sample at 105 for 4 h: it loses NMT 2.0% of its weight.
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in tight containers in a cool place.
• USP Reference Standards 11
11
USP Ensulizole RS 
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Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Behnam Davani, Ph.D., M.B.A.
Senior Scientific Liaison 1-301-816-8394 |
(SM12010) Monographs - Small Molecules 1 |
| Reference Standards | RS Technical Services 1-301-816-8129 rstech@usp.org |
USP35–NF30 Page 3046
Pharmacopeial Forum: Volume No. 35(4) Page 849