Properties of a low band gap conducting polymer electrode used for amperometric detection in liquid chromatography

Abstract

The performance characteristics of a conductive polymer, used as working electrode material in a wall-jet amperometric detector are described. The electrode coating consisted of a poly(5,6-dithio-octyl-1,3-dithienylisothianaphthene) layer. The material was coated on the surface of a glassy carbon electrode through evaporation from a dichloromethane solution. It is a low band gap polymer (1.41 eV), with an intrinsic conductivity of 10(-2) S cm(-1), which makes the use of a dopant unnecessary. Catecholamines were used as model substances in oxidative measurements. Detection limits in LC separations with 4.6 mm ID columns (1 mL min(-1) flow-rate) were 250 pg; the t(90) response time was 3 s. Quinones and nitrophenolics were studied in reductive measurements. The material could be used at negative potentials down to -800 mV (vs. SCE) without losing its electrocatalytic and conductive properties. The coating was competitive to glassy carbon in most respects and superior to polypyrrole. It showed group specificity in reductive measurements, e.g., quinones were reduced whereas nitrogroups (electroactive on glassy carbon) were not. The material can be used over a large potential range, shows good electrochemical activity and is very stable. It is suggested for use in modified electrodes.