A: Triturate a quantity of powdered Tablets, equivalent to about 0.5 g of thiabendazole, with about 20 mL of water, and filter. Wash the residue with 20 mL of water, discard the washing, dissolve the residue in 30 mL of 0.1 N hydrochloric acid, and filter. Collect the filtrate in a separator, render it alkaline with 1 N sodium hydroxide, and extract with 10 mL of carbon disulfide. Filter the carbon disulfide layer through a dry filter, collecting the filtrate in an evaporating dish. Evaporate the solvent with the aid of gentle heat and a stream of nitrogen. [Caution—Do not overheat the residue.] The residue so obtained responds to Identification test A under Thiabendazole.

B: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that of the Standard preparation as obtained in the Assay.

Procedure for content uniformity—

Standard preparation— Dissolve an accurately weighed quantity of USP Thiabendazole RS in 0.1 N hydrochloric acid, and dilute quantitatively and stepwise with 0.1 N hydrochloric acid to obtain a solution having a known concentration of about 5 µg per mL.

Test preparation— Transfer 1 Tablet to a 1000-mL volumetric flask, add about 75 mL of 0.1 N hydrochloric acid, and heat on a steam bath for about 1 hour. Cool to room temperature, dilute with 0.1 N hydrochloric acid to volume, mix, and filter a portion of the solution, discarding the first 20 mL of the filtrate. Pipet 5 mL of the filtrate into a 500-mL volumetric flask, dilute with 0.1 N hydrochloric acid to volume, and mix.

Procedure— Concomitantly determine the absorbances of the Standard preparation and the Test preparation at the wavelength of maximum absorbance at about 302 nm, with a suitable spectrophotometer, using 0.1 N hydrochloric acid as the blank. Calculate the quantity, in mg, of C10H7N3S in the Tablet taken by the formula: in which T is the labeled quantity, in mg, of thiabendazole in the Tablet, C is the concentration, in µg per mL, of USP Thiabendazole RS in the Standard preparation, D is the concentration, in µg per mL, of thiabendazole in the Test preparation, based upon the labeled quantity per Tablet and the extent of dilution, and AU and AS are the absorbances of the Test preparation and the Standard preparation, respectively.

(Official January 1, 2007)

Standard preparation and Chromatographic system—Prepare as directed in the Assay under Thiabendazole Oral Suspension.

pH 3.5 phosphate buffer— Dissolve 13.8 g of monobasic sodium phosphate in water to obtain 2000 mL of solution. Adjust this solution with phosphoric acid to a pH of 3.5 ± 0.05.

Mobile phase— Prepare a filtered and degassed mixture of pH 3.5 phosphate buffer and methanol (54:46). Make adjustments if necessary (see System Suitability under Chromatography 621).

Assay preparation— Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 200 mg of thiabendazole, to a 1000-mL volumetric flask, add 100 mL of 0.1 N hydrochloric acid, mix, and warm the solution for a minimum of 30 minutes. Allow to cool to room temperature, dilute with water to volume, mix, and filter, discarding the first 20 mL of the filtrate.

Procedure— Proceed as directed for Procedure in the Assay under Thiabendazole Oral Suspension. Calculate the quantity, in mg, of C10H7N3S in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Thiabendazole RS in the Standard preparation, and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.