Normal pulse voltammetry as improved quantitative detection mode for amperometric solvent polymeric membrane ion sensors

A normal pulse voltammetric detection mode for amperometric solvent polymer ic membrane ion sensors is described. These sensors function on the basis o f ion transfer voltammetry into an organic membrane phase of high viscosity . To avoid sensor drill, it is required that sample ions extracted within a measurement period are quantitatively stripped off the sensing membrane be fore the next measurement step. The time required for complete back extract ion of previously extracted ions must be substantially longer than for the uptake process. Indeed more than 40% of extracted ions are predicted to rem ain in the membrane phase if the stripping time equals the uptake time. Thi s suggests that cyclic voltammetry is generally an inadequate method for a reliable application/characterization of these sensors. The pulsed method i mposes discrete potential pulses onto the membrane that are incrementally c hanging with time to cover the total desired potential range. Between each uptake pulse a sufficiently long stripping pulse around 0V s applied. Optim ization of uptake and stripping times are performed, and comparative data w ith cyclic voltammetry are shown. Normal pulse voltammetric detection scans show strictly the current response for the ion uptake process, and are fre e of superimposed stripping waves. This characteristic aids in elucidating the nature of each observed wave and can therefore also be used for qualita tive purposes. The scans also show higher sensitivity than in classical cyc lic voltammetry. Experiments are here limited to ionophore-free membranes a s model systems.