A: Infrared Absorption á197Kñ:previously dried.

B: Ultraviolet Absorption á197Uñ—

Diluent— Prepare a mixture of 500mLof water,450mLof methanol,and 50mLof acetonitrile.

Mobile phase— Dissolve 6g of sodium 1-heptanesulfonate in 500mLof water,add 12mLof glacial acetic acid,2.0mLof triethylamine,450mLof methanol,and 50mLof acetonitrile,and mix.Pass through a suitable filter of 0.5µm or finer porosity.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Amprolium RSin Diluentto obtain a solution having a known concentration of about 0.5mg per mL.

Assay preparation— Transfer about 50mg of Amprolium,accurately weighed,to a 100-mLvolumetric flask,add Diluentto volume,and mix.

Resolution solution— Prepare a solution in Diluentcontaining about 0.5mg of USP Amprolium RSand 0.2mg of 2-picoline per mL.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×25-cm column containing packing L13.The flow rate is about 0.6mLper minute.Chromatograph the Resolution solution,and record the responses as directed for Procedure:the resolution,R,between amprolium and 2-picoline is not less than 7;the column efficiency determined from the amprolium peak is not less than 6500theoretical plates;the tailing factor for the analyte peak is not more than 2.3;and the relative standard deviation of the amprolium responses for replicate injections is not more than 1.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the areas for the major peaks.Calculate the quantity,in mg,of amprolium (C14H19ClN4·HCl)in the portion of Amprolium taken by the formula: in which Cis the concentration,in mg per mL,of USP Amprolium RSin the Standard preparation;and rUand rSare the amprolium peak responses obtained from the Assay preparationand the Standard preparation,respectively.