Indirect Spectrophotometric Determination of Benzocaine in Pharmaceutical Preparations

An indirect spectrophotometric method is developed for the determination of benzocaine as pure and in pharmaceutical preparations. The method is based on the oxidation of benzocaine with iron (III) in acidic medium, and the liberated iron (II) reacts with 1,10 -phenanthroline to produce ferroin complex which has a maximum absorption at 510 nm against reagent blank. Beer's law is valid over the concentration range of 5-80 µg benzocaine/25 ml and the molar absorptivity is 5.7 ×10 4 l.mol -1 .cm -1 , indicating high sensitivity. The common excipients and additives do not interfere in benzocaine determination. The proposed method is successfully applied to the assay of benzocaine in two synthetic preparations.