All solid-state contact poly vinyl chloride (PVC) membrane potassium-selective electrode has been developed. The construction of the ion selective electrode membrane was organized using ionophore 4,4'-bis[4"-phenoxy(15-crown-5) methyl] benzyl in PVC cocktail. The potentiometric performance characteristics of the electrode were investigated by a computerized system. The electrode was found highly selective to K+ ions over a wide variety of other cations. The electrode almost exhibited a Nernstian response (>= 55 (+/- 15) mV/decade of K activity) to K+ within the concentration range 1.5 x 10(-1)-1.0 x 10(-5) M. The operational pH range of the electrode was 5-7. The response time of the electrode was fast (< 10 s), and the life time was long (at least 2 months). The electrode has been successfully used in real sample analysis. The values obtained by the electrode were in good agreement with the certified values.