ION-TRANSPORT IN FREE AND SUPPORTED NITROBENZENE ALIQUAT NITRATE LIQUID MEMBRANE ION-SELECTIVE ELECTRODES .3. POTENTIOMETRIC LIMITS OF DETECTION AND SELECTIVITY

Limits of detection, as a function of ion exchanger loading, for tetrapentylammonium, tetrahexylammonium, tetraheptylammonium, and Aliquat nitrate in nitrobenzene, have been determined. The first three show rapid extraction equilibria and detection limits obey the Kamo, Hazemoto, and Kobatake extension of Buck's theory. More dilute loading gives improved (lower) detection limits. Aliquat nitrate gives evidence of kinetic control and reversal of detection limit dependence on loading. The detection limit may be determined by impurity anions at sub-micromolar concentrations. p]Selectivity coefficients for chloride ion, while concentration-dependent, improve with Aliquat loading. This result agrees with predictions in Part I, of this series, based on the observed decreases in dielectric constant with increased loading. The smaller ion is favored in the higher dielectric constant (more dilute) membranes. © 1979.