POTENTIOMETRIC DETECTION OF ORGANIC-ACIDS IN LIQUID-CHROMATOGRAPHY USING CONDUCTING OLIGOMER ELECTRODES

A conducting oligomer electrode was used for the potentiometric detect ion of organic acids in reversed phase liquid chromatography (LC). The conducting material consisted of a mixture of a phenylene vinylene tr imer with a polycarbonate host polymer and iodine. A glassy carbon ele ctrode was coated with this material by evaporation from a chloroform solution. A theoretical model was given to describe the observed poten tiometric responses. The analysis conditions were optimized to obtain both efficient separations, and sensitive potentiometric responses. De tection limits in the nanogram level were attained when a 1 mM phospho ric 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 high er than 5 nmol, and a linear dependence for injected amounts below thi s value. The response times of the electrode were smaller than 1 s at typical LC flow-rates. The reproducibility for consecutive injections was 5%. (C) 1998 Elsevier Science B.V. All rights reserved.