Lifetime of neutral carrier based ion-selective liquid-membrane electrodes

CONTENTS
11.1 Sampling 278
11.2 Storage and Preservation 279
11.3 Pretreatment of Samples 280
11.4 Digestion of Samples 281
11.5 Analytical Methods 28211.5.1 Classical Methods 282
11.5.2 Spectrophotometric Method 284
11.5.3 Flame Atomic Absorption SpectroscopyTechniques 285
11.5.4 Electrothermal Atomic Absorption Spectroscopy 286
11.5.5 Inductively Coupled Plasma Methods 287
11.5.6 Electrochemical Methods 28811.5.6.1 Voltammetric Techniques. 288
11.5.6.2 Potentiometric Techniques 28911.5.7 Ion Chromatography 289
11.5.7.1 Other Chromatographic Techniques 29011.5.8 Other Techniques 290
11.5.8.1 Luminescence 290
11.5.8.2 X-Ray Fluorescence Spectrometry 291
11.5.8.3 Neutron Activation Analysis 29111.5.9 The Particular Case of Mercury 291
11.6 Summary 292
Abbreviations 292
References 293Natural waters contamination is a worldwide distributed problem which deserves large
attention not only due to its environmental hazardous effects but also for the risks to the
human health as well as the economical damages it produces. Between the wide diversity
of pollutants affecting water resources heavy metals receive particular concern considering their strong toxicity even at low concentrations.

Heavy Metals, Major Metals, Trace Elements

Ammonium and potassium ion-selective membranes formulated with PVC/hydroxylated PVC, polyurethane/hydroxylated PVC, and moisture-curable silicone rubber matrices are studied in an effort to extend the lifetime of solid-state ion sensors through improved membrane adhesion. The PVC/membranes exhibit electrochemical performance equivalent to that of conventional PVC membranes in terms of slope, detection limit, and selectivity. The polyurethane- and silicone-rubber-based membranes have better adhesion to silicon nitride than do PVC or hydroxylated PVC matrices. Incorporating a silanizing reagent (silicon tetrachloride) significantly improves the adhesion of the polyurethane matrix. The use of silicon tetrachloride in membrane matrices also enhances the electrochemical stability of the interfacial potential between ion-selective polymer-matrix membranes and silver epoxy inner reference electrodes of solid-state sensors. The biocompatibility of the polymer matrices is examined via radiotracer protein adsorption studies and whole blood clotting time measurements. The polyurethane- and silicone-rubber-based membranes exhibit less overall nonspecific protein adsorption than the PVC or hydroxylated PVC matrices.

Electrochemical performance, biocompatibility, and adhesion of new polymer matrices for solid-state ion sensors.

Theoretical treatment of the dynamic response of ion-selective membrane electrodes

The preparation of a series of non-cyclic, uncharged ligands able to selectively complex alkali and alkaline earth metal cations is described. These molecules are designed to be used as carriers for cations through membranes. Some of the compounds show high Ca2+ and Na+ selectivity, respectively, in liquid membrane electrodes.

M. Vasák

Papers

A potassium-selective silicone-rubber membrane electrode based on a neutral carrier