ION-SELECTIVE FIELD-EFFECT TRANSISTORS - A SENSOR FOR LITHIUM AND CALCIUM

An Li-sensitive sensor based on a field-effect transistor with a tanta lum pentoxide gate and a poly(vinyl chloride) membrane based on diethy lene glycol bis-o-2-diphenylphosphinylmethll phenyl ether is developed . This sensor exhibits analytical characteristics close to those of a lithium-selective electrode analogous in membrane composition; it is i nsensitive to the concentration of hydrogen ions in the pH range 4.5-8 .5. The service life of the sensor is no shorter than four months, whi ch is comparable to the service Life of the corresponding ion-selectiv e electrode. A bifunctional sensor for Ca and Li is prepared based an membranes used for preparing the corresponding monofunctional ion-sele ctive field-effect transistors; this sensor exhibits analytical charac teristics close to those of ion-selective electrodes and monofunctiona l sensors.