A: Triturate a quantity of powdered Tablets,equivalent to about 0.5g of thiabendazole,with about 20mLof water,and filter.Wash the residue with 20mLof water,discard the washing,dissolve the residue in 30mLof 0.1Nhydrochloric acid,and filter.Collect the filtrate in a separator,render it alkaline with 1Nsodium hydroxide,and extract with 10mLof 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 Identificationtest Aunder Thiabendazole.

B: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that of the Standard preparationas obtained in the Assay.

Procedure for content uniformity—

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

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

Procedure— Concomitantly determine the absorbances of the Standard preparationand the Test preparationat the wavelength of maximum absorbance at about 302nm,with a suitable spectrophotometer,using 0.1Nhydrochloric acid as the blank.Calculate the quantity,in mg,of C10H7N3Sin the Tablet taken by the formula: in which Tis the labeled quantity,in mg,of thiabendazole in the Tablet,Cis the concentration,in µg per mL,of USP Thiabendazole RSin the Standard preparation,Dis 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 AUand ASare the absorbances of the Test preparationand the Standard preparation,respectively.

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

pH3.5phosphate buffer— Dissolve 13.8g of monobasic sodium phosphate in water to obtain 2000mLof solution.Adjust this solution with phosphoric acid to a pHof 3.5±0.05.

Mobile phase— Prepare a filtered and degassed mixture of pH3.5phosphate bufferand methanol (54:46).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

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

Procedure— Proceed as directed for Procedurein the Assayunder Thiabendazole Oral Suspension.Calculate the quantity,in mg,of C10H7N3Sin the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Thiabendazole RSin the Standard preparation,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.