Solid-state voltammetry and polymer electrolyte plasticization as a basis for an electrochemical gas chromatographic detector

Abstract

A new type of electrochemical gas chromatographic (ECGC) detector is described. The detector consists of a film of polymer electrolyte, PEO{sub 16}/LiCF{sub 3}SO{sub 3}, coating a microelectrode-based electrochemical cell and in contact with the effluent stream of a gas chromatograph. The PEO{sub 16}/LiCF{sub 3}SO{sub 3} polymer acts as an ionically conducting but physically rigid medium. Currents passed at the microelectrode/polymer interface depend on reactions of electroactive solutes dissolved in and diffusing through the polymer phase. These currents respond to the presence of sample components in the gas phase through their sorption into, and plasticization of, the PEO polymer phase. The polymer plasticization results in larger diffusion coefficients for the electroactive solutes and, consequently, larger microelectrode currents. Several forms of electrochemical potential control are examined as are the effects of chosen electroactive probe, probe concentration, polymer film thickness, and gaseous sample concentration and sorption. Faster detector responses are obtained with thin PEO{sub 16}/LiCF{sub 3}SO{sub 3} films and faster diffusing electroactive probes. The detector responds linearly to small quantities of sample but exponentially to large sample concentrations. The detector is unusual in that it is most sensitive to later-eluting components of a sample mixture; this effect results from the connection between themore » degree of sample component sorption or partition into the polymer electrolyte and the resulting degree of polymer plasticization and transport rate enhancement.« less