Ion-selective Liquid Membrane Research Articles

A Supersmall Single-Cell Nanosensor for Intracellular K + Detection

Intracellular potassium ions (K+) play pivotal roles in many physiological processes. Several K+ sensors have been developed for probing cellular K+ fluctuations. Nevertheless, the existing solutio...

Preparation of a ticlopidine potentiometric sensor and its application to pharmaceutical and biological analysis

Ticlopidine (Tic) ion selective liquid membrane electrode was constructed from poly (vinyl chloride) containing Tic-tetraphenylborate (Tic-TPB) as the sensing element in the presence of dioctylphthalate (DOP) as the plasticizing solvent mediator. The electrode shows nearly Nernstian response for the drug over the concentration range of 1.0×10−2–5.0×10−5M with cationic slope of 58.23mV per concentration decade, and the response time is very short (≤10s). The electrode potential is nearly stable over the pH range 3.8–5.4. The electrode exhibits good selectivity for the Tic with respect to a large number of inorganic ions, amino acids and some pharmaceutical substances. The sensor successfully was used for the determination of Tic in pharmaceutical and biological samples. The average recovery and RSD for the analysis of Tic in pharmaceutical and biological samples using the proposed method obtained 101.04, 98.90% and 1.14, 1.39%, respectively. The results are in good agreement with those obtained by voltammetry method.

鋳型樹脂を用いたジスプロシウム（III）イオン選択性電極の開発

A dysprosium(III)-imprinted polymer was prepared by an imprinting method using dysprosium(III) as the guest and styrene and methacrylate as the host, via a seed emulsion technique. The dysprosium(III)-imprinted polymer adsorbed dysprosium(III) ions more effectively than a non-imprinted polymer. The dysprosium(III) ion-selective liquid membrane electrode, comprising the dysprosium(III)-imprinted polymer (20 mg), polyvinyl chloride (75 mg), and plasticizer nitrophenyl octyl ether (80 mg), showed a Nernstian response of 19.3 mV dec−1 in the range of 10−7 ∼ 10−2 M. The selectivity coefficients of this electrode (log kpot) for potassium(I), copper(II), and samarium(III) ions were –3.71, –5.29, and –3.85, respectively. The electrode was also used for the determination of dysprosium(III) in river water.

Monitoring Ion Activities In and Around Cells Using Ion-Selective Liquid-Membrane Microelectrodes

Determining the effective concentration (i.e., activity) of ions in and around living cells is important to our understanding of the contribution of those ions to cellular function. Moreover, monitoring changes in ion activities in and around cells is informative about the actions of the transporters and/or channels operating in the cell membrane. The activity of an ion can be measured using a glass microelectrode that includes in its tip a liquid-membrane doped with an ion-selective ionophore. Because these electrodes can be fabricated with tip diameters that are less than 1 μm, they can be used to impale single cells in order to monitor the activities of intracellular ions. This review summarizes the history, theory, and practice of ion-selective microelectrode use and brings together a number of classic and recent examples of their usefulness in the realm of physiological study.

Determination of Apparent Formation Constants of Eu(III) with Humic Substances by Ion Selective Liquid Membrane Electrode

This is the novel measurement of the apparent formation constants of trivalent lanthanide with humic substances by potentiometric titration using an ion selective electrode (ISE) consisting of bis(diphenylphosphoryl)methane as an ionophore. The ISE prepared exhibited a Nernstian response to the Eu3+ concentration in the test solutions in the presence of humic acid and fulvic acid. The effect of the solution conditions, including the pH, initial metal and humic substance concentrations, and ionic strength, on the formation constants was examined. The present formation constants were compared with the reported data using solvent extraction method.

Formation Constants of Eu(III)–Carboxylates Determined by Ion-selective Liquid Membrane Electrode

Abstract A trivalent metal ion-selective electrode (ISE) consisting of bis(diphenylphosphoryl)methane as an ionophore was developed for the determination of formation constants with organic ligands. The ISE prepared exhibited Nernstian response to the concentration of Eu3+ in the test solutions. Even in the presence of carboxylic acids such as malonic acid in samples, the obtained potential values were found to be stable and reproducible during the measurement time. The present formation constants of Eu with carboxylates were in good agreement with the reported values.

Ion-selective electrodes for determination of fluoxetine in capsules and in biological fluids

Fluoxetine (FX) ion selective liquid membrane and coated wire graphite electrodes have been constructed from poly(vinyl chloride) containing FX-tetraphenylborate (FX-TPB) as the sensing element in the presence of DOP as the plasticizing solvent mediator. The two electrodes show nearly Nernestian response over the concentration range 2×10−5–1×10−2mol/L of the drug with slopes of 58.5 and 55.5mV/decade for the liquid membrane and the coated wire graphite electrodes, respectively. The electrodes exhibit good selectivity for the FX with respect to a large number of inorganic cations and organic substances of biological fluids. The method is precise as shown by the mean recoveries range of 100.50–101.04% and 99.69–100.17% with mean relative standard deviations 0.96–1.10% and 0.82–1.03% for liquid membrane and coated wire graphite electrodes, respectively. Fluoxetine is determined successfully in pure solutions and in capsules or in biological fluids using the standard additions and potentiometric titrations methods.

PH-Microscopy: technical application in phosphating solutions

The applicability of the pH-microscopy with microelectrodes based on H +-ion-selective liquid membranes is shown for phosphating solutions. Linear potential response is found at room temperature up to 60 °C with Nernst factors of −58 and −69 mV/pH, respectively. The investigation of an electrode surface activity by pH-imaging is demonstrated with surface scans above special designed test electrodes. The formation of pH-gradients due to the corrosion of steel in diluted phosphoric acid is examined in dependence on nitrite (accelerator) concentration, time and distance to the corroding surface ΔpH= f(c NO 2 , t, z). In a distance of 1 μm above the corroding steel surface the pH-shift within 100 s is ΔpH=0.08 with c(NaNO 2)=2.9 mM. The pH-shift increases up to ΔpH=0.8 with c(NaNO 2)=11.6 mM. The simulation of corrosion caused pH-gradients by electrochemical generated pH-gradients on an inert microdisk electrode allows the quantitative determination of the additional H +-consumption by nitrite. Therefore, the theory of spherical steady-state diffusion fields around microdisk electrodes is used.

Threshold ionic site concentrations required for Nernstian potentiometric responses of neutral ionophore-incorporated ion-selective liquid membranes.

An equation that can describe the concentrations of ionic sites required for a Nernstian potentiometric response slope of neutral ionophore-incorporated ion-selective liquid membranes is presented. This equation is derived from a model based on electrical diffuse layers on both the membrane and the aqueous sides of the interface, in which the phase boundary potential is correlated to the surface charge density as well as the salt concentrations in the bulk membrane and aqueous solution. To experimentally and accurately confirm the validity of this equation, response characteristics of field effect transistors covered by neutral ionophore-based liquid membranes with varying concentrations of a derivative of tetraphenylborate as an anionic site but free of ionic impurities were examined. The observed membrane potentials and the response slopes for membranes with various concentrations of anionic sites were in good agreement with the values calculated from the theory presented in this paper with the measured complexation stability constants for the relevant systems. This result indicates that the theoretical prediction based on the proposed equation for the anionic site concentration is accessible for the preparation of neutral ionophore-incorporated ion-selective liquid membranes, which show Nernstian response slopes for the primary ions.

Application of ion-selective microelectrodes to the detection of calcium release during bone resorption

In this work we apply calcium ion-selective liquid membrane microelectrodes to the investigation of the release of ionised calcium in real-time from bovine cortical bone slices in the presence of osteoclasts. The osteoclast is the cell responsible for the resorption (dissolution) of bone and excess bone resorption is implicated in diseases such as osteoporosis. Pretreatment of the bone slice with dilute solutions of ammonium fluoride was found to result in greater resistance to osteoclastic resorption. However, a detectable calcium flux was still observed indicating that the cells were able to attach to the fluoride treated bone and carry out resorption. These data were confirmed by scanning electron microscopy which indicated that the number of bone resorption pits was not affected by the fluoride treatment, although the excavated area was markedly decreased in the presence of fluoride. The results of these studies indicate that the use of calcium-selective microelectrodes provide a feasible alternative assay of osteoclast activity to the conventional electron microscopic assay. The microelectrode technique enables real-time data to be obtained, whereas the conventional method requires a long (ca. 16–20 h) incubation of the cells on the bone slice.

Partial blocking of ion transport at the interface of an ion-selective liquid membrane electrode by neutral surfactants: Experiments and computer simulation

Lipophilic neutral surfactants of the sugar alkyl ester type are experimentally observed to substantially increase the ion transfer impedance between an aqueous solution and ion-selective electrode membranes made from plasticized PVC with neutral carrier. The magnitude of the effect depends considerably on the molecular structure and on the concentration of the surfactant. Statistical thermodynamic simulation of the experimental system agrees qualitatively with the experimental observations.

Development of Separation and Quantification Methods for Organic Compounds Using Supercritical Fluids/Studies on Permselectivity at the Phase Boundary of Ion-Selective Liquid Membranes by Optical Phenomena as Probes for Phase-Boundary Potentials

Development of Separation and Quantification Methods for Organic Compounds Using Supercritical Fluids/Studies on Permselectivity at the Phase Boundary of Ion-Selective Liquid Membranes by Optical Phenomena as Probes for Phase-Boundary Potentials

Ion-Selective Liquid Membrane Electrode for Discrimination of Alkyllead Derivatives and Inorganic Lead Ions.

An investigation by using ion-selective electrodes on the discrimination of Pb2+ and R3Pb+, where R is an alkyl substituent, is the subject of the present paper. Selective macrocyclic thiacrown ethers are applied as active ligands. The response and selectivity of electrodes based on thiacrown ethers and ionophore-free electrodes towards inorgnaic lead ions and alkyllead substituents in model solutions and mazine cell sap are reported. The presented electrodes could be recommended as a relatively cheap and simple method for lead speciation.

Shift and drift of electromotive forces of solid-state electrodes with ion-selective liquid membranes

The behavior of electromotive forces (EMFs) of solid-state ion sensors, in which the interface between the ion-selective liquid membrane and the silver-silver chloride electrode is modified with a hydrophilic intermediate layer containing various concentrations and various kinds of electrolyte salts, are described in this study. The EMF of this sensor is significantly dependent on the concentrations and kinds of electrolyte salts in the intermediate layer. The solid-state ion sensor shows a stable EMF only when the intermediate layer contains the primary ions and chloride ions. This indicates that an efficient ion exchange process is necessary at all interfaces involved, including a thin water layer, for a stable EMF of the solid-state ion sensor. The resistance measurement shows that mechanical deterioration of the ion-selective membranes in the solid-state ion sensor with the optimized intermediate layer does not take place due to the osmolality difference as long as the ion-selective membrane adheres to the sensor body tightly. The long term stability of the solid-state ion sensor with the optimized intermediate layer was found to be sufficient for practical use.

Ion-sensitive microelectrode system with short response time

The measurement of changes in ion activity (e.g., pH) in neurons requires fine tip-sized double-barreled microelectrodes: one channel being equipped with an ion-selective liquid membrane, the other used for measurement of the membrane potential. The limited bandwidth and the differing transfer functions for electrical and ionic signals necessitate frequency response linearization networks to ensure that the output signal of the electrode is a faithful image of the input signal. We have developed a linearization network to ensure a rapid response time for ion-sensitive microelectrodes. To test the response characteristic we have developed a test system that allows the pH at the electrode tip to be changed within 1 ms. Application of these techniques to electrodes of 1 μm tip diameter results in a 90% response time to a pH step of ∼ 60 ms and of ∼ 2 ms with electrodes with 20 μm tip.

Ionic additives for ion-selective electrodes based on electrically charged carriers

The influence of ionic sites on the behavior of charged carrier-based ion-selective liquid membrane electrodes is described by theory and experiments for cation- and for anion-selective electrodes. The cation exchanger potassium tetrakis[3,5-bis-(trifluoromethyl)phenyl]borate proved to be a beneficial additive for nitrite-selective electrodes. On the other hand, the anion exchanger tridodecylmethylammonium chloride improved the potentiometric properties of cation-selective electrodes. By the incorporation of a defined amount of these sites, the selectivity was enhanced, the emf functions became theoretical, the electrode resistance was lowered, and the long-term stability improved. The optimal molar ratio of additive to ionophore was in the range of 0.3-0.6 for the ionophores studied

Characterization procedure for ion-selective electrode assays of magnesium activity in aqueous solutions of physiological composition

A magnesium ion-selective liquid membrane electrode based on a synthetic neutral carrier is presented. The selectivity for Mg2+ over Na+, K+, and H+ is sufficient for assays in the physiological range, but a chemometric correction of approximately 10% is still necessary for the Ca2+ interference. We optimized the membrane composition especially with respect to selectivity and accuracy by performing a new characterization procedure in which we simulated the variety of blood serum samples with 10 aqueous solutions. After a three-point calibration, these solutions were measured alternately with the middlerange calibrator for 3 min. The magnesium activity was evaluated after correcting for the calcium interference according to the Nikolsky equation. The selectivity coefficient, KpotMgCa, was itself fitted to give the minimum deviations from the assigned magnesium activities. Electrodes with an optimized membrane composition show an average deviation from theoretical activity values of about 1.6% with logKpotMgCa = -0.8.

Design and Preliminary Performance Characteristics of a Newly Proposed Reference Cell for Ionized Calcium in Serum

A novel flow-through design for a calcium ion-selective liquid membrane and half-cell is proposed. The membrane is based on a neutral carrier for calcium and has the same quantitative chemical composition as that used in most commercial analyzers for ionized calcium (iCa2+). The membrane and half-cell follow the specifications in the Stage 1, Draft 4 document for a Reference Method for iCa2+ of the IFCC Expert Panel on pH, Blood Gases, and Electrolytes. Measurements of iCa2+ in serum with this cell confirm prior observations that protein adsorption on the membrane surface causes a rapid but reversible shift in the cell calibration signal and possible systematic errors in the measurement of iCa2+ in serum. When the protein adsorption phenomenon is maintained at equilibrium during calibrations and sample measurements, the new cell can be used to reproducibly assign iCa2+ concentrations to serum pools. These calibrated pools may then be used as reference materials and to resolve the biases known to exist among commercial iCa2+ analyzers.

Neutral-Carrier-Based Ion-Selective Microelectrodes Design and Application

At present, neutral-carrier- and ¡on-exchanger-based ion-selective liquid membrane microelectrodes are available for the measurement of H+, Li+, Na+, K+, Mg2+, Ca2+, NH4+ and CI-. Fundamental aspects, design features and limitations of microelectrodes are discussed and examples for their application in physiology are given. The most important characteristics are summarized in view of intra- and extracellular physiological measurements. The selectivity coefficients KijPol with respect to the most common ions are compared to calculated values Kij,maxPol, required for measurements in intra- and extracellular samples without significant interference. For intracellular microelectrode studies, these required values are fully met for H+, K+, Mg2+, Ca2+ and CI-, while in the case of extracellular measurements H+, Na+, K+ and Ca2+ can be assayed adequately.

3,7‐Dioxaazelaamides as Ionophores for Lithium Ion Selective Liquid Membrane Electrodes

AbstractLipophilic neutral carriers were synthesized which show Li+/Na+ selectivities of up to ca. 80 in highly lipophilic liquid membranes. The sensor membranes exhibit improved response times and increased lifetimes as compared to systems described earlier. They allow reliable measurements of Li+ in blood serum within the clinical concentration range. A 1:1 Li+/ionophore complex of one representative (N,N,N′,N′‐tetracyclohexyl‐5,5‐dimethyl‐3,7‐dioxaazelaamide) has been prepared, and its structure was elucidated by X‐ray analysis.