A new potassium ion selective electrode is proposed, in which the KTiOPO4 single crystal membrane is used as the electroactive material. The slope of response is determined to be 58mV/-lgak by means of computer fitting. The selective coefficients in relation to Na^+ is 4.0 ×10^-^4. The advantages of this electrode are that its slope can be hardly influenced by the variation of the pH value; its stability, repeatability and its long ilfetime as well.

Key words: ION SELECTIVE ELECTRODE, SINGLE CRYSTALS, OPTICAL MATERIAL