Standard preparation— Dissolve a suitable quantity of USP Pramoxine Hydrochloride RS,accurately weighed,in 0.5Nsulfuric acid,and dilute quantitatively with the same solvent to obtain a solution having a known concentration of about 150µg per mL.

Assay preparation— [NOTE—If emulsions form,2to 5mLof alcohol may be added to separate the phases.]Transfer an accurately weighed quantity of Jelly,equivalent to about 15mg of pramoxine hydrochloride,to a small beaker,and dissolve the Jelly in 0.1Nsulfuric acid,using four 5-mLportions,warming each portion on a steam bath,and transferring to a 125-mLseparator.Shake the separator vigorously after each transfer to complete dissolution of the Jelly.To the cooled solution in the separator add 20mLof ether,shake carefully,and proceed as directed for Assay Preparationunder Salts of Organic Nitrogenous Bases á501ñ,beginning with “filter the acid phase into a second 125-mLseparator,”except to combine the final 0.5Nsulfuric acid extracts in a 100-mLvolumetric flask,dilute with the acid to volume,and mix.

Procedure— Proceed as directed under Salts of Organic Nitrogenous Bases á501ñ,diluting 20.0mLeach of the Standard preparationand the Assay preparationwith 0.5Nsulfuric acid to 50.0mL,and determining the absorbances at the wavelength of maximum absorbance at about 286nm.Calculate the quantity,in mg,of C17H27NO3·HCl in the portion of Jelly taken by the formula: in which Cis the concentration,in µg per mL,of USP Pramoxine Hydrochloride RSin the Standard preparation.