A: Triturate a quantity of powdered Tablets,equivalent to about 10mg of thiamine hydrochloride,with 10mLof 0.5Nsodium hydroxide,and filter.Using a 5-mLportion of the filtrate,proceed as directed in Identificationtest Bunder Thiamine Hydrochloride Injection,beginning with “then add 0.5mLof potassium ferricyanide TS”:the specified reaction is observed.

B: Triturate a quantity of powdered Tablets,equivalent to about 10mg of thiamine hydrochloride,with 10mLof water,and filter:treated separately,2-mLportions of the filtrate yield a red-brown precipitate with iodine TSand a white precipitate with mercuric chloride TS,and respond to the tests for Chloride á191ñ.

C: To the remainder of the filtrate prepared for the preceding test add 1mLof lead acetate TSand 1mLof 2.5Nsodium hydroxide:a yellow color is produced.Heat the mixture for several minutes on a steam bath:the color changes to brown,and,on standing,a precipitate of lead sulfide separates.

Medium: water;900mL.

Apparatus 2: 50rpm.

Time: 45minutes.

Procedure— Determine the amount of C12H17ClN4OS·HCl dissolved,employing the procedure set forth in the Assay for niacin or niacinamide,pyridoxine hydrochloride,riboflavin,and thiamineunder Water-Soluble Vitamins Tabletsusing filtered portions of the solution under test,suitably diluted with Dissolution Mediumif necessary,in comparison with a Standard solution having a known concentration of USP Thiamine Hydrochloride RSin the same Medium.

Tolerances— Not less than 75%(Q)of the labeled amount of C12H17ClN4OS·HCl is dissolved in 45minutes.

Standard preparation— Prepare as directed for Standard Preparationunder Thiamine Assay á531ñ.

Assay preparation— Place not fewer than 20Tablets in a flask of suitable size,half fill the flask with 0.2Nhydrochloric acid,and heat on a steam bath,with frequent agitation,until the tablets have dissolved or have disintegrated so that a uniform dispersion is obtained.Cool,transfer the contents of the flask to a volumetric flask,and dilute with 0.2Nhydrochloric acid to volume.If the mixture is not clear,either centrifuge it or filter it through paper known not to adsorb thiamine.Dilute a portion of the clear solution quantitatively and stepwise with 0.2Nhydrochloric acid to obtain a solution containing about 0.2µg of thiamine hydrochloride per mL.Using this as the Assay Preparation,proceed as directed for Procedureunder Thiamine Assay á531ñ.