Final answer:
The Nikolsky-Eisenman (NE) Equation has limitations like neglecting interference from other ions and not accounting for mixed potentials. More accurate models include a modified NE Equation with extra coefficients obtained through calibration to improve selectivity descriptions.
Step-by-step explanation:
The Nikolsky-Eisenman (NE) Equation is used in ion-selective electrodes to model the electrode’s response to different ions in a solution. While it is helpful, there are certain limitations. One limitation is that it assumes that the response is solely based on the ionic activities, neglecting interference from other ions. Moreover, it does not account for mixed potentials when multiple ions can bind to the electrode surface, leading to a deviation from the ideal behavior predicted by the NE Equation.
A more accurate equation for modeling selectivity is the modified Nikolsky-Eisenman equation or an empirically derived equation that takes into account the diverse interactions between the ions and the electrode surface, often specific to the particular system under study. These equations usually involve extra coefficients that are obtained through calibration, accounting for the selectivity coefficient of interfering ions, hereby providing a more precise description of an ion-selective electrode's selective behavior.