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-dimethylaminocinnamaldehyde 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-microgram/ml range. Best accuracy can be obtained for solutions containing 0.25--1.25  microgram/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.
D001566:Benzocaine / Q000032:analysis*; D003124:Colorimetry; D008722:Methods; D009824:Ointments / Q000032:analysis; D013488:Suppositories / Q000032:analysis; D013607:Tablets / Q000032:analysis
D009824:Ointments; D013488:Suppositories; D013607:Tablets; D001566:Benzocaine