A: Infrared Absorption á197Kñ.

B: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

C: It meets the requirements of the tests for Chloride á191ñ.

pH7.5Phosphate buffer— Dissolve 8.71g of dibasic potassium phosphate in about 800mLof water,adjust with dilute phosphoric acid (1in 10)to a pHof 7.5±0.1,add water to make 1000mL,and mix.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and pH7.5Phosphate buffer(55:45).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Pramoxine Hydrochloride RSin Mobile phaseto obtain a solution having a known concentration of about 0.5mg per mL.

Assay preparation— Transfer about 50mg of Pramoxine Hydrochloride,accurately weighed,to a 100-mLvolumetric flask,dissolve in and dilute with Mobile phaseto volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 224-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The column temperature is maintained at 40,and the flow rate is about 2mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency is not less than 1500theoretical plates;the tailing factor is not more than 1.5;and the relative standard deviation for replicate injections is not more than 1.5%.

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 C17H27NO3·HCl in the portion of Pramoxine Hydrochloride taken by the formula: in which Cis the concentration,in mg per mL,of USP Pramoxine Hydrochloride RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.