Determination of eugenol by using a Briggs - Rauscher system catalyzed by a macrocyclic nickel (II) complex

Abstract

This paper reports a new method for determination of tracing amounts of eugenol (EUG) by its perturbation effects on a novel Briggs–Rauscher (BR) oscillating system catalyzed by a macrocyclic complex [NiL](ClO4)2. The ligand L in the complex is 5, 7, 7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene. In this novel BR oscillator, not only a macrocyclic complex was used as a catalyst to replace Mn2+, but the value of pH in the system was kept at pH of stomach fluids (pH ≈2.0) as well. Experimental results have shown that addition of EUG into the BR system could quench and then successively regenerate the oscillations, accompanying by an inhibitory time that relies on the concentration of the EUG added. An assay was thus established by employing such a BR system for determining EUG. The relationship between inhibition time and EUG concentrations is obtained over the range between 5.00×10−7–2.50×10−5M. Two calibration curves are thus achieved: linear regression over the range 5.00×10−7 to 1.25×10−5M of EUG, and polynomial regression over the range 1.25×10−5 ∼ 2.50×10−5M of EUG. The obtained RSD from seven measurements of 1.00×10−5M of EUG is 3.75%, and from 1.50×10−5M of EUG is 2.05%. Some factors influencing the determination were also examined. Not only has the method been successfully applied to determine EUG but it could be extended to determine other lipophilic antioxidants as well. Furthermore, the possible reaction mechanism using the FCA model has been proposed.