Ultraviolet Absorption of Local Anesthetics with an Aromatic Amino Group as a Function of pH

¹ Division of Chemistry, American Dental Association, Chicago, Illinois

The ultraviolet absorption from 200 to 360 mµ of a representative group of para- and meta-aminobenzoic acid ester local anesthetics in solutions with a pH of 0.1-8 was determined. Correlations of the chemical structure with ultraviolet absorption of these compounds and the effect of the pH of the solution on the ultraviolet absorption were discussed. The apparent dissociations, as determined by the spectrophotometric method, and the isosbestic points of these compounds were described. The utility of these data in analytical procedures involved with these compounds and other compounds with pH-dependent and non-pH-dependent ultraviolet absorption spectra was discussed.