PROGRAMMABLE SELECTIVE INEXPENSIVE POTENTIOMETRIC DETECTOR FOR FLOW-INJECTION ANALYSIS - POTASSIUM DETERMINATION WITH A NAFION MEMBRANE MODIFIED ELECTRODE

The study of a nafion membrane (ISE membrane) for the inexpensive pote ntiometric detection of potassium ion in a flow injection system is re ported. The nafion membrane doped with potassium ion showed that excel lent selectivity could be achieved for various cations, except for Rb, and some interference for Cs+. A linear potential response of 10(-2) - 10(-6) M for the potassium ion was obtained with a detection limit of about 0.5 x 10(-6) M. This approach can be employed for constructin g a potentiometric detector for virtually any cation (soluble at basic pH values) by simply changing the electrode pretreatment (or doping s olution).