(Official January 1, 2007)

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

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

Procedure— To the Standard preparation and also to the Assay preparation add 5 mL of 6 N ammonium hydroxide, then treat each as follows. Extract with five 25-mL portions of chloroform, and filter the combined extracts through about 1 g of anhydrous sodium sulfate supported on a pledget of glass wool. Receive the filtrate in a 200-mL volumetric flask, add chloroform to volume, and mix. Transfer 3.0 mL of this solution to a 100-mL volumetric flask, add chloroform to volume, and mix. Concomitantly determine the absorbances of both solutions at the wavelength of maximum absorbance at about 280 nm, with a suitable spectrophotometer, using chloroform as the blank. Calculate the quantity, in mg, of C13H20N2O2·HCl in each mL of the Injection taken by the formula: in which W is the weight, in mg, of USP Procaine Hydrochloride RS used, V is the volume, in mL, of Injection taken, and AU and AS are the absorbances of the solutions from the Assay preparation and the Standard preparation, respectively.