VOLTAMMETRY OF P-BENZOQUINONE AND ANTHRACENE AT POLY(ETHYLENE OXIDE)-COATED MICROELECTRODES IN CO2-BASED FLUIDS

A device that combines a working and counter electrode connected to ea ch other via a poly(ethylene oxide) film containing electrolyte forms a self-contained electrochemical cell that has been-used to inspect th e voltammetry of p-benzoquinone and anthracene in CO2-based fluids. In terest in the voltammetry of these compounds in CO2-based fluids is de rived from their potential amenability to electrochemical detection co upled to supercritical fluid separations. With appropriate formulation of the poly(ethylene oxide) films, both compounds may be voltammetric ally detected in CO2 with or without the use of polar fluid modifiers. The compatibility of voltammetry with modified and unmodified fluids, as demonstrated herein,is a feature lacking from most presently avail able detectors used in supercritical fluid chromatography. Furthermore , following electroreduction, both compounds are susceptible to electr ophilic addition by CO2 to yield carboxylated compounds. This provides an opportunity to investigate CO2-based fluids as a reagent as well a s a medium for electrochemistry. Evidence is obtained that the rate of the carboxylation reaction which follows reduction of each compound i s enhanced in CO2-based fluids compared to the rate of carboxylation i n CO2-saturated acetonitrile. The enhanced rate observed in CO2-based fluids is attributed to the greater availability of CO2 for the reacti on.