Standard preparation— Transfer to a 125-mLseparator about 50mg,accurately weighed,of USP Procaine Hydrochloride RS,and dilute with water to 20mL.

Assay preparation— Transfer to a 125-mLseparator an accurately measured volume of Injection,equivalent to about 50mg of procaine hydrochloride,and dilute with water to 20mL.

Procedure— To the Standard preparationand also to the Assay preparationadd 5mLof 6Nammonium hydroxide,then treat each as follows.Extract with five 25-mLportions of chloroform,and filter the combined extracts through about 1g of anhydrous sodium sulfate supported on a pledget of glass wool.Receive the filtrate in a 200-mLvolumetric flask,add chloroform to volume,and mix.Transfer 3.0mLof this solution to a 100-mLvolumetric flask,add chloroform to volume,and mix.Concomitantly determine the absorbances of both solutions at the wavelength of maximum absorbance at about 280nm,with a suitable spectrophotometer,using chloroform as the blank.Calculate the quantity,in mg,of C13H20N2O2·HCl in each mLof the Injection taken by the formula: in which Wis the weight,in mg,of USP Procaine Hydrochloride RSused,Vis the volume,in mL,of Injection taken,and AUand ASare the absorbances of the solutions from the Assay preparationand the Standard preparation,respectively.