Fenbendazole
Carbamic acid, [5-(phenylthio)-lH-benzimidazol-2-yl]-, methyl ester. Methyl 5-(phenylthio)-2-benzimidazolecarbamate [43210-67-9]. » Fenbendazole contains not less than 98.0 percent and not more than 101.0 percent of C15H13N3O2S, calculated on the dried basis.
Packaging and storage
Preserve in well-closed, light-resistant containers, and store at 25, excursions permitted between 15 and 30.
Labeling
Label it to indicate that it is for veterinary use only.
USP Reference standards 11
USP Fenbendazole RS . USP Fenbendazole Related Compound A RS . USP Fenbendazole Related Compound B RS . USP Mebendazole RS .
Identification,
Infrared Absorption 197K.
Loss on drying 731
Dry it at 100 to 105 for 3 hours: it loses not more than 1.0% of its weight.
Residue on ignition 281:
not more than 0.3%.
Heavy metals, Method II 231:
not more than 10 µg per g.
Related compounds
Solution A
Prepare a mixture of water, methanol, and acetic acid (70:30:1).
Solution B
Prepare a mixture of methanol, water, and acetic acid (70:30:1).
Mobile phase
Use variable mixtures of Solution A and Solution B as directed for Chromatographic system.
Hydrochloric methanol
Prepare a mixture of methanol and hydrochloric acid (99:1).
Standard solution 1
Dissolve an accurately weighed quantity of USP Fenbendazole RS in Hydrochloric methanol to obtain a solution having a known concentration of about 5 mg per mL. Dilute 1.0 mL of this solution with methanol to 200.0 mL. Dilute 5.0 mL of this solution with Hydrochloric methanol to 10.0 mL. This solution contains about 0.0125 mg of USP Fenbendazole RS per mL.
Standard solution 2
Dissolve an accurately weighed quantity of USP Fenbendazole Related Compound A RS in methanol to obtain a solution having a known concentration of about 0.1 mg per mL. Dilute 1.0 mL of this solution with Hydrochloric methanol to 10.0 mL, and mix.
Standard solution 3
Dissolve an accurately weighed quantity of USP Fenbendazole Related Compound B RS in methanol to obtain a solution having a known concentration of about 0.1 mg per mL. Dilute 1.0 mL of this solution with Hydrochloric methanol to 10.0 mL, and mix.
Resolution solution
Dissolve 10.0 mg of USP Fenbendazole RS and 10.0 mg of USP Mebendazole RS in 100.0 mL of methanol. Dilute 1.0 mL of this solution with Hydrochloric methanol to 10.0 mL, and mix.
Test solution
Dissolve 50.0 mg of Fenbendazole in 10.0 mL of Hydrochloric methanol.
Chromatographic system (see Chromatography 621
The liquid chromatograph is equipped with a 280-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L1. The flow rate is about 1 mL per minute. The chromatograph is programmed as follows.
Procedure
Separately inject equal volumes (about 10 µL) of Standard solution 1, Standard solution 2, Standard solution 3, and the Test solution into the chromatograph, record the chromatograms, and measure the area responses for all of the peaks. Calculate the percentages of fenbendazole related compound A and of fenbendazole related compound B in the portion of Fenbendazole taken by the formula:
0.1(C/W)(ri / rSi)
in which C is the concentration, in mg per mL, of USP Fenbendazole Related Compound A RS or USP Fenbendazole Related Compound B RS in Standard solution 2 or Standard solution 3, as appropriate; W is the weight, in mg, of Fenbendazole taken to prepare the Test solution; ri is the peak area response of the relevant related compound obtained from the Test solution; and rSi is the peak area response of the relevant related compound obtained from Standard solution 2 or Standard solution 3, as appropriate. Not more than 0.5% of either related compound is found. Calculate the percentage of any other impurity in the portion of Fenbendazole taken by the formula:
0.1(C/W)(ri / rS)
in which C is the concentration, in mg per mL, of USP Fenbendazole RS in Standard solution 1; W is as defined above; ri is the peak area response of any impurity other than fenbendazole related compound A or fenbendazole related compound B obtained from the Test solution; and rS is the peak area response of the main peak in the chromatogram obtained from Standard solution 1. Disregard any impurity peak with a response that is less than one-fifth that of rS. Not more than 0.5% of any other impurity is found. The sum of all impurities found, including fenbendazole related compound A and fenbendazole related compound B, is not more than 1%.
Assay
Dissolve about 200 mg of Fenbendazole, accurately weighed, in 30 mL of glacial acetic acid, warming if necessary to effect solution. Cool, and titrate with 0.1 N perchloric acid VS, determining the endpoint potentiometrically. Each mL of 0.1 N perchloric acid is equivalent to 29.94 mg of C15H13N3O2S.
Auxiliary Information
Please check for your question in the FAQs before contacting USP.
Chromatographic Column
USP32NF27 Page 2350
Pharmacopeial Forum: Volume No. 30(4) Page 1205
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.
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