Colorimetric Analysis of Procaine Hydrochloride

A colorimetric assay procedure was developed for the quantitative analysis of procaine hydrochloride. The method is based on the interaction of procaine hydrochloride with p-dimethylaminocinnamaldehyde in the presence of trichloroacetic acid in absolute methanol to form a red Schiff base which can be quantitated spectrophotometrically at 547.5nm. The Beer–Lambert law was adhered to over the 0.1–7-μg/ml range. Best accuracy was attained for solutions containing 0.4–4 μg/ml. The color was stable for at least 70 min. The method was applied to procaine hydrochloride injections, both with and without epinephrine, without prior separation of the drug. The results were comparable to those obtained by the official procedures.