Colorimetric determination of procaine hydrochloride in pharmaceutical preparations.

A new rapid, specific, and convenient colorimetric method for the determination of procaine hydrochloride in pharmaceutical preparations is described. This method is based on measurement of the intensity of the orange-red color developed when procaine hydrochloride is allowed to react with 1,2-naphthoquinone-4-sulfonic acid sodium salt in aqueous solution. Beer's law is followed over 6.0--20.0 micrograms/ml. The method was applied to the determination of procaine hydrochloride in procaine hydrochloride, procaine hydrochloride injection with or without epinephrine, penicillin G procaine, penicillin G procaine injection, and fortified procaine penicillin injection (BP). The results were comparable to those obtained by official procedures. Because of its simplicity, sensitivity, and accuracy, this method is particularly suited for routine analysis of official preparations of procaine hydrochloride.