Fig. 5. Overcoming ISFET cross sensitivities.

a The changes in I_ds for the different cation ISFETs with respect to concentrations of the cations, using the separate solution method. Linear fits were used to extract the Nikolskii selectivity coefficients. b Comparison of the measured K⁺ and ${\mathrm{NH}}_4^{+}$ concentrations by applying the Nikolskii-Eisenman formalism and the as prepared concentrations. The as prepared concentrations are determined from the solution volume and mass of the added salts. c Comparison of the measured Na⁺ and ${\mathrm{NH}}_4^{+}$ concentrations by applying the Nikolskii-Eisenman formalism and the as prepared concentrations.