The combination of flow-injection analysis (FIA) and chemically modified ion-sensitive field-effect transistors (CHEMFETs) is described. In a wall-jet cell, two identical potassium-selective CHEMFETs were used for a differential measurement using a platinum (pseudo-)reference electrode. Silicone-rubber membrane materials, chemically bound to the SiO2 gate oxide, were used with valinomycin as the ionophore. The optimized FIA system showed a linear response of 56 mV per decade for potassium concentrations above 5 × 10−5 M. Preliminary results of potassium determinations in human serum and urine samples are presented.
van der Wal, P. D., Sudhölter, E. J. R., & Reinhoudt, D. N. (1991). Design and properties of a flow-injection analysis cell using potassium-selective ionsensitive field-effect transistors as detection elements. Analytica chimica acta, 245, 159-166. https://doi.org/10.1016/S0003-2670(00)80216-0