Figure 3. The potential of the procaine-sensitive microelectrode was measured by changing the pH value of 1 mM procaine dissolved in the intracellular-like solution (plots). The change in pH did not affect the response of procaine-sensitive microelectrode at pH 8.0 or lower. The electric response to the change in the ratio of procaine ionization with pH alteration was simulated by modified Nernstian Equation includingK⁺interference (pK^aof procaine = 9.06, slope = 53, selectivity coefficient = 1.9 x 10^-4; curve), and compared with the measured values. Although the potential changed at >pH 8, the plots corresponded to the curve within a range between pH 8 and 10, and the change in the potential would result from a response not to proton concentration but to the changed ratio of procaine ionization. The measured values were lower than the curve at >pH 10, and it meant that pH would affect the electrode performance.