Spectrophotometric Determination of Benzocaine by Azo-Dye Formation Reaction with N - (1-naphthyl)ethylenediamine as Coupling Agent

A simple spectrophotometric method for the determination of benzocainein aqueous solution is developed. The method based on the coupling ofdiazotized benzocaine with N-(1-naphthyl)ethylenediamine(N-NED) in acidicrnedium. The purplish - violet azo dye formed is water soluble, stable, andshows tnaximum absorption at 547.5 nm. Beer's law is obeyed over the range10 - 100 ptg I 25 ml, i.e, 0.4 - 4 ppm with a molar absorptivity of 5.56 x 104l.mol-r.cm-' and Sandell's sensitivity index of 0.0029 pg.cm-2, arelative errorof - 0.660 to * 0.002% and a relative standard deviations of*0.110to+ 0.550% depending on the concentration. The method has been applied todetermine benzocaine in two synthetic pharmaceutical preparations.