Colorimetric Assay of Benzocaine and Some Dosage Forms

A colorimetric procedure for benzocaine and a number of its dosage forms was developed; it offers improvement in ease, speed, and sensitivity over the official method. The method is based on the formation of a red Schiff base between benzocaine and p-dimethylaminocinnam- aldehyde in a nonaqueous acidic medium. At the maximum absorption of 544 nm, the Beer-Lambert law was adhered to over the 0.025–2.5-μg/ml range. Best accuracy can be obtained for solutions containing 0.25–1.25 μg/ml. The color was stable for at least 2 hr. Analysis of benzocaine in the dosage forms studied can be directly performed without prior drug extraction.