A: Infrared Absorption 197K.

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

C: It meets the requirements of the tests for Chloride 191.

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

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and pH 7.5 Phosphate buffer (55:45). Make adjustments if necessary (see System Suitability under Chromatography 621).

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

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

Chromatographic system (see Chromatography 621)— 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 2 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the column efficiency is not less than 1500 theoretical 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 20 µL) of the Standard preparation and the Assay preparation into 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 C is the concentration, in mg per mL, of USP Pramoxine Hydrochloride RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.