NOTE—Throughout the following procedures,protect test or assay specimens,the Reference Standard,and solutions containing them,by conducting the procedures without delay,under subdued light,or using low-actinic glassware.

A: Infrared Absorption á197Kñ.

B: It responds to the tests for Chloride á191ñ.

Standard preparation and Standard dilutions—Dissolve an accurately weighed quantity of USP Promethazine Hydrochloride RSin methylene chloride to obtain a solution containing 10.0mg per mL(Standard preparation).Prepare a series of quantitative dilutions of the Standard preparationin methylene chloride to contain 0.2,0.1,0.05,and 0.025mg per mL(Standard dilutions)corresponding to 2.0%,1.0%,0.5%,and 0.25%of impurities,respectively.

Test solution— Dissolve 100mg,accurately weighed,of Promethazine Hydrochloride in 10.0mLof methylene chloride.

Procedure— Using a 20-×20-cm thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of silica gel mixture,apply 10-µLportions of the Test preparation,the Standard preparation,and each of the Standard dilutions2.5cm from the lower edge of the plate.Develop the plate in an unsaturated tank containing a mixture of ethyl acetate,acetone,alcohol,and ammonium hydroxide (90:45:2:1).After the solvent has moved not less than 10cm,air-dry the plate,and view under short-wavelength UVlight:the RFvalue of the principal spot obtained from the Test preparationcorresponds to that from the Standard preparation.Estimate the concentration of any other spots observed in the lane for the Test preparationby comparison with the Standard dilutions:the sum of the impurities is not greater than 2.0%,and no single impurity is greater than 1.0%.