A: Infrared Absorption á197Kñ.

B: It responds to the Thin-Layer Chromatographic Identification Test á201ñ.Prepare the test solution by dissolving an accurately weighed quantity of Chlorpropamide in acetone to obtain a solution containing 1mg per mL.Develop the chromatogram in a solvent system consisting of a mixture of methylene chloride,methanol,cyclohexane,and ammonium hydroxide (100:50:30:10).

Mobile phase— Prepare a filtered and degassed mixture of equal volumes of acetonitrile and dilute glacial acetic acid (1in 100).[NOTE—Do not exceed 50%of acetonitrile.]Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Chlorpropamide RSin Mobile phase,and dilute quantitatively,and stepwise if necessary,with Mobile phaseto obtain a solution having a known concentration of about 0.05mg per mL.

Assay preparation— Transfer about 50mg of Chlorpropamide,accurately weighed,to a 100-mLvolumetric flask,add Mobile phaseto volume,and mix.Transfer 10mLof this solution to a second 100-mLvolumetric flask,add Mobile phaseto volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 240-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed under Procedure:the tailing factor for the analyte peak is not more than 1.5,and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C10H13ClN2O3Sin the portion of Chlorpropamide taken by the formula: in which Cis the concentration,in mg per mL,of USP Chlorpropamide RSin the Standard preparation,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.