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

The performance characteristics of a conductive polymer, used as working el ectrode material in a wall-jet amperometric detector are described. The ele ctrode coating consisted of a poly(5,6-dithio-octyl-1,3-dithienylisothianap hthene) layer. The material was coated on the surface of a glassy carbon el ectrode through evaporation from a dichloromethane solution. It is a low ba nd 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 separati ons 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 reductiv e measurements. The material could be used at negative potentials down to - 800 mV (vs. SCE) without losing its electrocatalytic and conductive propert ies. The coating was competitive to glassy carbon in most respects and supe rior to polypyrrole. It showed group specificity in reductive measurements, e.g., quinones were reduced whereas nitrogroups (electroactive on glassy c arbon) were not. The material can be used over a large potential range, sho ws good electrochemical activity and is very stable. It is suggested for us e in modified electrodes.