Thiabendazole
(thye'' a ben' da zole).
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201.251H-Benzimidazole, 2-(4-thiazolyl)-.
2-(4-Thiazolyl)benzimidazole
[148-79-8].» Thiabendazole contains not less than 98.0 percent and not more than 101.0 percent of C10H7N3S, calculated on the dried basis.
[note—Thiabendazole labeled solely for veterinary use is exempt from the requirements of the tests for Residue on ignition, Selenium, Heavy metals, and Chromatographic purity. ]
Packaging and storage—
Preserve in well-closed containers.
USP Reference standards 
11
—
11—
USP Thiabendazole RS 
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Identification—
A:
Infrared Absorption 197K—Do not dry specimens.
197K—Do not dry specimens.
C:
Dissolve about 5 mg in 5 mL of 0.1 N hydrochloric acid, add 3 mg of p-phenylenediamine dihydrochloride, and shake to dissolve. Add about 0.1 g of zinc dust, mix, and allow to stand for 2 minutes. Add 5 mL of a solution prepared by dissolving 20 g of ferric ammonium sulfate in 75 mL of water, adding 10 mL of 1 N sulfuric acid, and diluting with water to 100 mL: a blue or blue-violet color develops.
D:
The RF value of the principal spot in the chromatogram of the Identification test preparation corresponds to that of Standard preparation A, as obtained in the test for Chromatographic purity.
Loss on drying 731
—Dry it in vacuum at 100
for 2 hours: it loses not more than 0.5% of its weight.
731
—Dry it in vacuum at 100 for 2 hours: it loses not more than 0.5% of its weight.
Melting range 741:
between 296 and 303.
741:
between 296 and 303.
Residue on ignition 281:
not more than 0.1%.
281:
not more than 0.1%.
Selenium 291:
0.003%, a 200-mg test specimen being used.
291:
0.003%, a 200-mg test specimen being used.
Heavy metals, Method II 231:
0.001%.
231:
0.001%.
Chromatographic purity—
Standard preparations—
Dissolve USP Thiabendazole RS in glacial acetic acid, and mix to obtain a solution having a known concentration of 1.0 mg per mL. Dilute quantitatively with glacial acetic acid to obtain Standard preparations A, B, and C having the following compositions:
| Standard
preparation |
Dilution | Concentration (µg RS per mL) |
Percentage (%, for comparison with test specimen) |
|---|---|---|---|
| A | (1 in 4) | 250 | 0.5 |
| B | (3 in 20) | 150 | 0.3 |
| C | (1 in 20) | 50 | 0.1 |
Test preparation—
Dissolve an accurately weighed quantity of Thiabendazole in glacial acetic acid to obtain a solution containing 50 mg per mL.
Identification preparation—
Dilute a portion of the Test preparation quantitatively with glacial acetic acid to obtain a solution containing 0.25 mg per mL.
Procedure—
Apply separately 10 µL of the Test preparation, 10 µL of the Identification preparation, and 10 µL of each Standard preparation to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture. Position the plate in a chromatographic chamber, and develop the chromatograms in a solvent system consisting of a mixture of toluene, glacial acetic acid, acetone, and water (60:20:8:2) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, and allow the solvent to evaporate. Examine the plate under short-wavelength UV light, and compare the intensities of any secondary spots observed in the chromatogram of the Test preparation with those of the principal spots in the chromatograms of the Standard preparations. No secondary spot from the chromatogram of the Test preparation is larger or more intense than the principal spot obtained from Standard preparation (0.5%), and the sum of the intensities of all secondary spots obtained from the Test preparation corresponds to not more than 1.0%.
621) coated with a 0.25-mm layer of chromatographic silica gel mixture. Position the plate in a chromatographic chamber, and develop the chromatograms in a solvent system consisting of a mixture of toluene, glacial acetic acid, acetone, and water (60:20:8:2) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, and allow the solvent to evaporate. Examine the plate under short-wavelength UV light, and compare the intensities of any secondary spots observed in the chromatogram of the Test preparation with those of the principal spots in the chromatograms of the Standard preparations. No secondary spot from the chromatogram of the Test preparation is larger or more intense than the principal spot obtained from Standard preparation (0.5%), and the sum of the intensities of all secondary spots obtained from the Test preparation corresponds to not more than 1.0%.
Assay—
Dissolve about 160 mg of Thiabendazole, accurately weighed, in 10 mL of glacial acetic acid. Add 50 mL of acetic anhydride, 1 mL of mercuric acetate TS, and 2 drops of crystal violet TS, and titrate with 0.1 N perchloric acid VS (the color change at the endpoint is from blue to blue-green). Perform a blank determination, and make any necessary correction. Each mL of 0.1 N perchloric acid is equivalent to 20.13 mg of C10H7N3S.
Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Leonel M. Santos, Ph.D.
Senior Scientific Liaison 1-301-816-8168 |
(SM12010) Monographs - Small Molecules 1 |
| Reference Standards | RS Technical Services 1-301-816-8129 rstech@usp.org |
USP35–NF30 Page 4833
Pharmacopeial Forum: Volume No. 29(1) Page 126