A flow-through cell was designed that can be used for flow-injection analysis with two chemically modified ion-sensitive field-effect transistors (CHEMFETs) in close proximity. This offers the possibility of a differential measurement without influence of the liquid junction potential. The differential signal of a potassium- and a sodium-selective CHEMFET responded in a Nernstian manner and selectively towards potassium in an excess (fixed) concentration of sodium. A highly lead-selective CHEMFET was used in the same flow cell in combination with a potassium-selective CHEMFET.
Cobben, P. L. H. M., Cobben, P. L. H. M., Egberink, R. J. M., Bomer, J. G., Schouwenaar, R., Brzozka, Z., ... Bos, M. (1993). Chemically modified ion-sensitive field-effect transistors: elimination of the liquid junction potential in a double sensor flow-injection analysis cell. Analytica chimica acta, 276(2), 347-352. https://doi.org/10.1016/0003-2670(93)80403-8