Alan Ceresa

Influence of key parameters on the lower detection limit and response function of solvent polymeric membrane ion-selective electrodes

The lower detection limit of conventional polymeric membrane ion-selective electrodes (ISEs) is given by the release of measuring ions from the sensor membrane into the aqueous sample. It can be greatly improved by using inner solutions of appropriate composition. Recently, steady-state model calculations have been used to predict the influence of various parameters on the response function and the lower detection limit. Among these, effects of the composition of the inner solution, the presence of interfering ions in the sample, the use of a flow-through cell, the polymer content and thickness of the ISE membrane, and the concentration of the membrane components have been investigated in the present work. All observed trends agree fully with the theoretically predicted ones.

Determination of formal complex formation constants of various Pb2+ ionophores in the sensor membrane phase

Abstract Formal complex formation constants of seven ionophores with Pb 2+ and a series of interfering cations have been determined in the organic membrane phase. To this purpose, potentiometric selectivities of the target ions relative to tetramethylammonium are compared for ion-exchanger- and ionophore-based ion-selective electrode membranes. Furthermore, information on the stoichiometry of the complexes formed is obtained from measurements with two membranes of different ionophore concentrations. Surprisingly, the results show that ionophores having thioamide are less efficient in coordinating Pb 2+ than corresponding ones with oxamide. The formal complex formation constants found are in excellent agreement with those determined by bulk optode measurements. A generally applicable method is proposed to gain more insight with a view to designing ligands and optimizing sensor membrane compositions.

Making use of ion fluxes through potentiometric sensor membranes: ISEs with step responses at critical ion activities

Note: 246 Reference SAMLAB-ARTICLE-2001-027 Record created on 2009-05-12, modified on 2016-08-08