Carrier Membrane Research Articles

Response Time Curves of Neutral Carrier Membrane Electrode of Tubular Shape

Abstract A tubular flow-through electrode system for measuring the response time curves under the step change of concentration using an ammonium ion-selective poly(vinyl chloride) membrane electrode was described. The response time data are analyzed by the curve fitting method using two theoretical equations, which are an exponential type equation based on an assumption of the film diffusion and a square root type one based on that of the diffusion within the membrane, and a semiempirical equation of hyperbolic type. A method of curve fitting in which the equilibrium potential is regarded as an unknown parameter was described in detail. The initial part of the response time curves, where the potential change is large, was fitted by the exponential type equation, while the following part close to the equilibrium potential was fitted by the square root type one. The semiempirical equation could also be fitted to the wide range of the curves. The dependence of the time constant of the exponential type equation upon the flow rate of sample solution is examined; the results firmly supports both the film diffusion as a determining process for the initial part of the curve and the reliability of the present experimental system.

515—Cation and anion responses of zwitterion phospholipid bilayers

The electrochemical behavior of zwitterion phospholipid bilayers as determined with the help of membrane potential data, is examined. The synthetic DL-β,γ-dipalmitoyl-α-phosphatidylcoline bilayer shows at 30°C nernstian and sub-nernstian anion responses which depend on the cation present in the electrolytes (LiCl, NaCl, KCl, CsCl, CaCl 2, CeCl 3), and in some cases on the concentration of the solutions considered. On the other hand, nernstian cation responses have been observed in non-isothermal membrane-potential measurements performed on the same lipidic films. These experimental results are explained on the assumption that, from a potentiometric viewpoint the phospholipid membrane behaves as a neutral carrier membrane electrode. Accordingly, the form of the potential equations, and then the anion response of the bilayer, follows from the chemistry of the phospholipid molecules.

Cation and anion responses of zwitterion phospholipid bilayers

The electrochemical behavior of zwitterion phospholipid bilayers as determined with the help of membrane potential data, is examined. The synthetic DL-β-γ-dipalmitoyl-α-phosphatidylcoline bilayer shows at 30°C nernstian and sub-nernstian anion responses which depend on the cation present in the electrolytes (LiCl, NaCl, KCl, CsCl, CaCl 2, CeCl 3), and in some cases on the concentration of the solutions considered. On the other hand, nernstian cation responses have been observed in non-isothermal membrane-potential measurements performed on the same lipidic films. These experimental results are explained on the assumption that, from a potentiometric viewpoint the phospholipid membrane behaves as a neutral carrier membrane electrode. Accordingly, the form of the potential equations, and then the anion response of the bilayer, follows from the chemistry of the phospholipid molecules.

Kontinuierliche intraoperative Meßwertregistrierung von Na + , K + und Ca ++ mit Carrier-Membran-Disk-Elektroden

The application of a two-channel flow-through analyzer with carrier membrane disc electrodes for the electrochemical analysis of heparinized blood, plasma or serum is described, its capabilities discussed and results of direct patient measurements presented.

Activity and interference effects in measurement of ionized calcium with ion-selective electrodes.

We assessed the magnitude of the errors in ionized-calcium measurements resulting from changes in electrolyte composition for three different ion-selective electrodes: the Orion Model 93-20, the Radiometer F2112, and the Simon neutral carrier membrane electrode. We attempted to distinguish between errors arising from changes in calcium ion activity and those due to interferences in the electrode response. Variation in sodium ion concentration over the range 100--180 mmol/liter produces changes in apparent ionized-calcium concentration that are largely attributable to activity effects for the Radiometer and Simon electrodes. The Orion electrode is subject to an additional sodium-interference effect. Apparent ionized calcium concentration measurements are independent of pH for the Radiometer electrode but not for the Orion electrode; the Simon electrode exhibits intermediate pH response, which is probably clinically negligible. Magnesium and potassium ions have little effect on ionized calcium concentration measurements, particularly when these ions are incorporated into calibration standards.

Optimizing Permselectivity for Neutral Carrier Membrane Electrodes

Abstract A new format: solvent, support and surface coating, has been discovered which greatly improves the response time and linearity of response of valinomycin-based potassium ion selective electrodes. With the new system completely Nernstian responses are obtained up to 0.1 M for aqueous potassium salt solutions of oil insoluble through slightly oil soluble anions (fluoride through perchlorate in the Hofmeister series), and nearly Nernstian responses are obtained for potassium salts having more oil soluble anions, including picrate. Electrodes using the new format have characteristic short response times (30 secs. for 90% steady state), long life-times and freedom from “memory effects”.

Synthetic Polymeric Membranes: Practical Applications - Past, Present and Future

Abstract

Anion responses and potential functions for neutral carrier membrane electrodes

Anion responses and potential functions for neutral carrier membrane electrodes

Uphill transport induced by counterflow.

1. In a membrane transport system containing a mobile carrier with affinities for two substrates a concentration gradient with respect to one of the substrates under certain conditions is able to induce an "uphill" transport (against the concentration gradient) of the other. 2. In a kinetic treatment quantitative conditions for such a "flow-induced uphill transport" and some of its characteristics are derived. 3. Experimentally the uphill transport of labelled glucose induced by a concentration gradient for mannose or unlabelled glucose is demonstrated in the human red cell. 4. It is shown that the flow-induced uphill transport is a feature characteristic for mobile carrier systems only and is not to be expected in systems in which the substrate is bound to a fixed membrane component ("adsorption membrane"), although such a system may yield identical transport kinetics. Also with respect to Ussing's flux ratio the two systems are different, the adsorption membrane meeting Ussing's criterion, the carrier membrane not. 5. It is concluded that the transport system in the human red cells must contain a mobile carrier, identical for glucose and mannose.