Potentiometric detection of organic acids in liquid chromatography using conducting oligomer electrodes

Abstract

A conducting oligomer electrode was used for the potentiometric detection of organic acids in reversed phase liquid chromatography (LC). The conducting material consisted of a mixture of a phenylene vinylene trimer with a polycarbonate host polymer and iodine. A glassy carbon electrode was coated with this material by evaporation from a chloroform solution. A theoretical model was given to describe the observed potentiometric responses. The analysis conditions were optimized to obtain both efficient separations, and sensitive potentiometric responses. Detection limits in the nanogram level were attained when a 1 mM phosphoric acid solution was used as the eluent, which were comparable to the values obtained with low-wavelength UV detection. Calibration curves showed a logarithmic dependence on an injected amount for amounts higher than 5 nmol, and a linear dependence for injected amounts below this value. The response times of the electrode were smaller than 1 s at typical LC flow-rates. The reproducibility for consecutive injections was 5%.