Characterization of keto-enol tautomerism of p-hydroxyphenylpyruvic acid using CE with amperometric detection and spectrometric analysis

Abstract

A high-performance CE with amperometric detection (CE-AD) was employed for the kinetic study of keto-enol tautomerism of p-hydroxyphenylpyruvic acid (pHPP). Several factors (concentration of β-cyclodextrin (β-CD), concentration and pH of running buffer, separation voltage and injection time) affecting CE-AD were investigated and separation conditions were optimized. The kinetics of pHPP was performed in water solution and phosphate solution under different pH and temperature, the homologous ketonization rate constants and half-life were obtained. Also, the activation energy was calculated according to the rate constants under different temperature. The experimental results indicated that β-CD played an important role in the separation, therefore UV spectrometric method was applied for the study of complexation interaction between ketonic pHPP and β-CD. The results indicated that the stoichiometric ratio of the pHPP-β-CD complex was 1:1 and formation constant was determined. The obtained kinetic results are in correspondence with those reported by our group with CE-UV. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.