The chemistry of the ion-selective optode has recently been recognized as a highly selective ion-sensing methodology which involves a highly selective complexation between an ionophore and a primary ion. This simple methodology allowed the construction of several kinds of ion-sensing devices which enabled highly selective ion determination for analytical purposes. In this review, sensing devices are divided into the following four types with different analytical uses: (1) flow analytical devices (flow-through optode); (2) waveguide devices (waveguide optode); (3) sensing plate devices (sensing plate optode, film optode); (4) fiber-optic devices (fiber optode). The characteristics of each device are explained and discussed with experimental data, and the future prospects for ion-selective optode methodology are described. Copyright (C) 1999 Elsevier Science B.V.
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