Membrane model for neutral-carrier-based membrane electrodes containing ionic sites

Abstract

The selectivity characteristics of neutral-carrler-based electrodes can be Improved to a large extent by the optimization of the Ionic sHes/carriers ratio. A new membrane model and a new equation for the emf response of such membranes are Introduced. They Illustrate the dependence of the emf response on the activity of free carriers available. As a case of practical Importance the emf function of a magnesium ion-selective electrode Is discussed. It demonstrates that the emf function normally deviates from the Nlkolsky-type behavior and that transient potentials and long-term drifts occur and therefore make the selectivity determination according to the separate solution method questionable. The measured data are In good agreement with the values calculated on the bads of the reported model.

An optical sensor for mercury ion based on the fluorescence quenching of tetra(p-dimethylaminophenyl)porphyrin

“…Suppose a complexation equilibrium between Hg 2+ in the aqueous solution (aq) and TDMAPP in the plasticized PVC membrane phase (org) is established with formation of a complex with a complexing ration of m:n, the overall equilibrium can be represented as follows [7][8][9]:…”

“…In fact, much research work has been performed to develop fluorescent sensors for the detection of transition and heavy metal ions [3][4][5][6], which offer distinct advantages in terms of sensitivity, selectivity and response time. Also, the theoretical basis of such optical membranes based on plasticized PVC has been well established [7][8][9]. The porphyrins are a class of naturally occurring macrocyclic compounds, which play a very important role in the metabolism of living organisms.…”

Flow-Injection Potentiometry by Poly(vinyl chloride)-Membrane Electrodes with Diphosphoryl-dicarboxylicacid-p-tert-butylcalix[4] arene Ionophore for the Determination of Th(IV) Ions

“…8,14,[16][17][18][19][20][21][22][23][24][25][26][27][28] This is due to the influence of the plasticizer on the dielectric constant of the membrane phase, the mobility of the ionophore molecules and the state of the ligands. 23,24 As can be seen from Table 1, among four different plasticizers used, DOP resulted in the best response slope and linearity.…”

A Comparison of Neutral Mg2+-Selective Ionophores in Solvent Polymeric Membranes: Complex Stoichiometry and Lipophilicity

“…tetraphenylborate salt) to the neutral carrier-based membranes provides lipophilic anionic sites in the polymeric electrode membranes, which support the selective extraction of Mg 2+ , and have been shown also to be favourable in other aspects. 2,15,16 The concentration of anionic sites affects the selectivity of an electrode, primarily by controlling the concentrations of both the exchangeable cations, and the free ionophore available for complexation at the membrane/solution interface. The optimum composition of a Mg 2+ -selective membrane with respect to the borate/ligand ratio is estimated by taking the charge number of interfering ions and the theoretical stoichiometry of ion-ligand complex into account.…”