A: It yields a white precipitate with mercuric chloride TS,and a red-brown precipitate with iodine TS.It also yields a precipitate with mercuric-potassium iodide TS,and with trinitrophenol TS.

B: Dilute a portion of Injection with water to a concentration of about 10mg of thiamine hydrochloride per mL.To 0.5mLof this solution add 5mLof 0.5Nsodium hydroxide,then add 0.5mLof potassium ferricyanide TSand 5mLof isobutyl alcohol,shake the mixture vigorously for 2minutes,and allow the liquid layers to separate:when illuminated from above by a vertical beam of UVlight and viewed at a right angle to this beam,the air-liquid meniscus shows a vivid blue fluorescence,which disappears when the mixture is slightly acidified,but reappears when it is again made alkaline.

C: It responds to the tests forChloride á191ñ.

Mobile phase,Internal standard solution,Standard preparation,and Chromatographic system— Prepare as directed in theAssay underThiamine Hydrochloride Elixir(Oral Solution,Official June 1,2005).

Assay preparation— Quantitatively dilute an accurately measured volume of Injection withMobile phase to obtain a solution containing about 500µg of thiamine hydrochloride per mL.Pipet 10mLof the resulting solution and 10mLofInternal standard solution into a 100-mLvolumetric flask,dilute withMobile phase to volume,and mix.

Procedure— Proceed as directed forProcedure in theAssay underThiamine Hydrochloride Elixir Oral Solution,(Official June 1,2005).Calculate the quantity,in mg,of thiamine hydrochloride (C12H17ClN4OS·HCl)in each mLof the Injection taken by the formula: in whichCis the concentration,in mg per mL,of USP Thiamine Hydrochloride RSin theStandard preparation;Lis the labeled quantity,in mg per mL,of thiamine hydrochloride in the Injection;Dis the concentration,in mg per mL,of thiamine hydrochloride in theAssay preparation on the basis of the labeled quantity and the extent of dilution;andRUandRSare the ratios of the peak responses of thiamine to methylparaben obtained from theAssay preparation and theStandard preparation,respectively.