A: Infrared Absorption á197Kñ—Dry specimens at 105for 2hours.

B: Asolution (1in 50)responds to the tests for Chloride á191ñ.

Solution A ,Solution B,and Mobile phase—Prepare as directed in the Assay.

Test solution— Dissolve quantitatively an accurately weighed quantity of Thiamine Hydrochloride in Mobile phaseto obtain a solution having a concentration of about 1.0mg per mL.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 4.0-mm ×15-cm column that contains packing L1.The flow rate is about 0.75mLper minute.

Procedure— Inject about 10µLof the Test solutioninto the chromatograph,and allow the Test solutionto elute for not less than three times the retention time of the main peak.Record the chromatogram and measure the areas of the peak responses:the total of the responses of all secondary peaks is not greater than 1.0%of the total of the responses of all of the peaks.

Solution A— Prepare a 0.005Msolution of sodium 1-octanesulfonate in dilute glacial acetic acid (1in 100).

Solution B— Prepare a mixture of methanol and acetonitrile (3:2).

Mobile phase— Prepare a mixture of Solution Aand Solution B(60:40),filter,and degas.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Internal standard solution— Transfer 2.0mLof methylbenzoate to a 100-mLvolumetric flask,dilute with methanol to volume,and mix.

Standard preparation— Dissolve an accurately weighed quantity of USP Thiamine Hydrochloride RSin Mobile phaseto obtain a solution having a known concentration of about 1mg per mL.Transfer 20.0mLof this solution to a 50-mLvolumetric flask,add 5.0mLof Internal standard solution,dilute with Mobile phaseto volume,and mix to obtain a Standard preparationhaving a known concentration of about 400µg per mL.

Assay preparation— Transfer an accurately weighed quantity of about 200mg of Thiamine Hydrochloride to a 100-mLvolumetric flask,dissolve in and dilute with Mobile phaseto volume,and mix.Transfer 10.0mLof this solution to a 50-mLvolumetric flask,add 5.0mLof Internal standard solution,dilute with Mobile phaseto volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 4-mm ×30-cm column that contains packing L1.The flow rate is about 1mLper minute.[NOTE—The flow rate may be adjusted as needed to obtain a retention time of about 12minutes for thiamine hydrochloride.]Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the resolution,R,between the thiamine and methylbenzoate peaks is not less than 4.0;the tailing factor for the thiamine peak is not more than 2.0;the column efficiency determined from the thiamine peak is not less than 1500theoretical plates;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the areas of the major peaks.Calculate the quantity,in mg,of C12H17ClN4OS·HCl in the Thiamine Hydrochloride taken by the formula: in which Cis the concentration,in µg per mL,of USP Thiamine Hydrochloride RSin the Standard preparation;and RUand RSare the ratios of the peak areas of thiamine to methylbenzoate obtained from the Assay preparationand the Standard preparation,respectively.