Bruno Rusterholz

Synthesis and characterization of neutral hydrogen ion-selective chromoionophores for use in bulk optodes

Abstract The type of ion-selective sensors discussed is based on a solvent polymeric membrane with optical transduction (bulk optode), and requires a reversible mass transfer of analyte ions into and from the bulk of the organic phase. Apart from the ion to be analysed, such sensors simultaneously measure a reference ion. For analytical purposes, an H + -selective carrier absorbing light in the visible range (chromoionophore) is incorporated in the membrane together with an ionophore as known from ion-selective electrodes. A series of neutral H + -selective chromoionophores, synthesized with a view to their possible use in bulk optodes, are described. The results of various studies on the basicity in different solvents, lipophilicity, chemical stability, selectivity, molar absorption coefficients and absorbance maxima are given and, in part, discussed theoretically. It is shown that the chromoionophores described are highly selective and offer a wide range of basicities. Their lipophilicity usually guarantees a long lifetime for applications in both aqueous solutions and diluted blood and serum, but for measurements in undiluted blood samples they should be covalently immobilized to the polymer of the optode membrane. Their chemical stability is usually sufficient, only direct sunlight causing decomposition.

Monitoring Pb2+ with optical sensing films

Abstract A new lipophilic ionophore, N,N,N′,N′ -tetradodecyl-3,6-dioxaoctane-1-thio-8-oxodiamide (ETH 5493), is characterized in optical sensing films with a view to being used for environmental monitoring. It sufficiently discriminates all alkali and alkaline earth metal ions and, contrary to what is observed with the corresponding dithioamide, does not suffer from irreversible changes upon contact with Ag + and Hg 2+ salts. Different response functions are found for bulk optodes with ratios of chromoionophore/ion exchanger above and below 1.0. The data obtained fit the theoretical response function with a standard deviation of the residuals of 0.0012 absorbance units (AU) without any systematic error. When comparing different membranes, the precision is still high (±0.0029 AU) but the residuals show a certain systematic trend.

Very lipophilic sodium-selective ionophore for chemical sensors of high lifetime

Abstract Ionophores based on 1,2-phenylenedioxydiacetamides with water/1-octanol partition coefficients up to 10 17 were synthesized. They have sufficient lipophilicity to be used in solvent-polymeric membranes for optrodes, ISFETs and ion-selective electrodes with a lifetime from 10 × 10 4 hours even in permanent contact with whole blood or undiluted blood serum. Selectivities of Na + over K + , Ca 2+ and Mg 2+ of 10 1.5 –10 2 and 10 4 , respectively, were obtained.

Critical parameters and optimization of a magnesium-selective liquid membrane electrode for application to human blood serum

SummaryThe selectivity of a new magnesium ionophore (ETH 7025) induced in membranes of different compositions is experimentally studied in view of the ion activities in human serum. The required selectivity coefficient against calcium for the application of an ion-selective magnesium electrode to human serum is calculated for the worst case. Other critical parameters for the application of a liquid PVC-based ion-selective membrane to undiluted human serum discussed are: the sensor lifetime which is related to the lipophilicity of the carrier as well as the ruggedness of the membrane against interactions with components of the relatively lipophilic sample.

Magnesium selective electrodes for blood serum studies and water hardness measurement

Magnesium selective ionophores are described which induce a rejection of Na+ and K+ in solvent polymeric membranes by factors of up to 6300 and 5000, respectively. Depending on the membrane composition, ion selective electrodes may be obtained with equal selectivity for Mg2+ and Ca2+ as well as sensors with a discrimination of Ca2+ by a factor up to 8. Sensors of the type described are candidates for water hardness determination as well as for an Mg2+ assay in blood by chemometric procedures.

Development of magnesium-selective ionophores

Abstract The syntheses of new magnesium-selective ionophores together with selectivity and 13 C NMR measurements are presented. Ion-selective electrodes based on the ionophore 1,3,5-tris[10-(1-adamantyl)-7,9-dioxo-6,10-diazaundecyl]-benzene (ETH 5506) showed excellent magnesium selectivity over calcium and potassium. Selectivity coefficients log K Pot MgCa = −1.9 and log K Pot MgK = −3.7 are observed. The conformational influence of different amide substituents was examined using 13 C NMR spectrometry. Two different series of isologue ionophores were studied. In both instances the addition of bulky substituents increased the ionophore selectivity of magnesium.

Influence of structural changes on the ion selectivities of magnesium ionophores based on malonic acid diamides

In an investigation of octamethylene bis(malonic acid diamides) and their selectivities for magnesium, it was found that presence of secondary amides within the particular ionophore played a considerable role in the enhancement of magnesium selectivity. Similar effects in other ionophores, i.e. tris(malonic acid diamides), were thus systematically looked at with the help of selectivity measurements with the hope of optimizing the number of secondary and tertiary amides so as to improve the magnesium selectivity. The syntheses of several investigated tris(malonic acid diamide) isologues are equally reported.

The coupling 2J(119Sn−O−13CO) in tributyltin acetate

The observation of a single coupling between the carbonyl carbon atom and the tin center in tributylin acetate proves that monomeric structures predominate in diluted CDCl3 solution at low temperatures (< 38°C). At higher temperatures (above 38°C) no coupling can be observed due to a fast intermolecular exchange of the acetate groups.