Chronocoulometric flow-injection analysis with solvent polymeric membrane ion sensors

Abstract

A method to carry out chronocoulometric measurements with solvent polymeric membrane ion sensors in flow-injection systems has been developed. For this, a double potential step was synchronised to the passage of the sample plug through the detector cell. A four-electrode potentiostat with ohmic drop compensation and a new flow-through cell to incorporate the four-electrode and the membrane were developed. A plasticized poly(vinyl chloride) (PVC) membrane containing TBATBP was used and the procedure was applied to the determination of tetraethyl-ammonium. The effect of the electrochemical and flow-injection variables was studied. In the selected conditions, a linear relationship between the quantity of electricity and tetraethyl-ammonium concentration was obtained in the range 5×10 −7–5×10 −5 M. The detection limit was 7×10 −8 M. Good repeatability and between day reproducibility were obtained. The potential application to other quaternary ammonium ions including acetylcholine was also studied.