K+-selective PVC membrane electrodes based on 6 bis-crown ethers (I-VI) were prepared with o-nitrophenyl octyl ether as the plasticizer and Ag/AgCl as the internal ref. electrode. The electrodes were evaluated vs. SCE. The potential responses of the electrodes are linearly proportional to log K+ concentration in the range 10-5-102 mol dm-3 K+. The electrodes containing II and III exhibit Nernstian response with a slope of 54-56 mV/decade. The selectivity of the electrodes to other alkali and alkaline earth metal ions was examined and the results showed the electrodes with high selectivity to K+.

Key words: CROWN ETHER COMPOUNDS, ION SELECTIVE ELECTRODE, POLYVINYL CHLORIDE, SECONDARY AMINE, MEMBRANE ELECTRODES, POTASSIUM ION, SCHIFF BASE