Potassium selective CHEMFET based on an ion-partitioning membrane

The use of a novel type of electroactive ion-partitioning membrane is emplo yed for the development of a potassium selective chemically modified field- effect transistor (CHEMFET). As is in the case of opt-odes, the membrane is doped with two ion carriers, one selective to the ion of interest (K+) and the other to protons. The careful optimization of the chemical composition of the membrane allows for ion-exchange to take place between the partitio ned cation and the membrane protons. The potassium ions extracted into the bulk of the membrane phase displace protons of equal charge out of the memb rane, and towards the sample solution and the pH-sensitive transducer. The potentiometric response of the sensor is based on the magnitude of this pro ton flux, as it is measured by the pH-ISFET. Both the effect of the ionic c omposition of the sample solution and the chemical constituents of the poly meric membrane are evaluated in relation to the potentiometric response of the CHEMFET. It is shown that the increase of the mole ratios of potassium to proton in the sample solution, the use of small amounts of a highly acid ic proton carrier, and the use of a low dielectric constant plasticizer of the sensor to potassium ions. The performance of the K-CHEMFET developed ba sed on the optimized ion-partitioning membrane is evaluated by the measurem ent of potassium levels in real blood serum samples. (C) 2001 Elsevier Scie nce B.V. All rights reserved.