Selective Polymeric Membrane Research Articles

Optimum composition of neutral carrier based pH electrodes

A simple formalism for the quantitative description of the upper and lower detection limit of pH selective solvent polymeric membrane electrodes containing a neutral carrier and a lipophilic anionic additive is presented, which is based on the consideration of phase transfer equilibria at the sample/membrane interface. It is shown that the lower and upper detection limits are controlled by the activity and lipophilicity of the interfering ions and by the basicity of the ionophore. When interfering cations or anions have completely penetrated the organic phase boundary layer through ion exchange or coextraction equilibria, respectively, the electrode response is expected to be a Nernstian function of the interfering ion activity alone. The measuring range may be shifted by incorporating ionophores of different basicity in the membrane, but cannot be extended with this approach. Instead, a high concentration of ionophore, together with 50 mol-% anionic additive relative to the ionophore, and, most importantly, a more hydrophobic membrane matrix with less cation binding characteristics has to be chosen for achieving a maximum measuring range of the potentiometric sensor.

Responses of H + selective solvent polymeric membrane electrodes fabricated from modified PVC membranes

Potentiometric responses of a novel class of pH sensitive ionophores, namely several phenoxazine derivatives, were tested in different modified PVC matrices. The ionophores were compounded into liquid membranes as usual or were covalently coupled to the polymeric matrix. The general analytical performance of the membranes and other membrane characteristics ( i.e., resistance and response time, as measures of membrane decomposition or structural changes) were followed in time. The transient responses of membranes with mobile ionophores in high molecular weight (HMW) and carboxylated PVC (PVC-COOH) were compared to those with immobilized ionophores. The response time of membranes with immobilized ionophores was found to be between those with mobile ionophores in HMW (fast response) and PVC-COOH (sluggish response). Accordingly, the rate of response was correlated primarily to the -COOH content of the membranes.

Removal of arsenic from groundwater using reagent binding/membrane separation

AbstractA hybrid method incorporating selective polymeric binding and membrane separation was used for the removal of arsenic from contaminated groundwater. Two types of polymers, polyethylenimine (PEI) and poly‐diallyl dimethyl ammonium chloride (DADMAC) and an ultrafiltration membrane were used at various concentrations and pH. Bench‐scale tests demonstrated a high degree of arsenic removal. The retention of arsenic was also determined in the presence of various background salts such as NaCl, NaNO3, Na2SO4, Na2CO3. Retention was found to depend on the concentration and type of anion present in solution.

Design of ionophore-free H +-selective solvent polymeric membranes for further biomedical applications

Ionophore-free H +-selective solvent polymeric membrane electrodes based on aminated poly(vinyl chloride) (PVC-NH 2) are studied. Among the large number of amino-PVC derivatives, the electrodes fabricated from piperazine-modified PVC show the best analytical performances. The new pH electrodes exhibit a Nernstian response between pH 4 and pH 12, and their selectivity coefficients toward biologically interesting cations match the corresponding values of H + electrodes based on TDDA or ETH 5294. The new membrane material offers additional prospects for ion-selective electrode fabrication with technologies used in microelectronic device development.

Ion-selective electrodes in organic analysis: primary amine selective polymeric membrane electrodes based on a calix[6]arene ionophore

Primary alkylamine selective electrodes were designed based on the host—guest interaction between calixarene ionophore and alkylammonium ions. The poly(vinyl chloride)(PVC) membrane electrode contains 1–3% m/m of an ester derivative of calix[6]arene as the neutral carrier and dioctyl phthalate as the plasticizer. At pH 3.2, the electrode exhibits a Nernstian response in the range 1 × 10–1–3 × 10–4 mol l–1 hexylamine with a slope of 57.5 ± 0.8 mV per concentration decade. The electrode. The electrode has a fast response time of less than 1 min and a constant Nernstian response after 1 month of continuous measurement. In contrast to the traditional PVC ion-exchange membrane electrode, the present electrode system was found to be highly selective to primary amines. Hence, the primary amine content of a mixture of amines can be determined using the electrode with good accuracy and precision.

SODIUM-SELECTIVE POLYMERIC MEMBRANE ELECTRODES BASED ON CALIX[4]ARENE DERIVATIVES

Four kinds of lipophilic calix[4]aryl ester derivatives (A)-(D) have been designed for Na+-selective polymeric membrane electrodes. On the ion selectivity of (A)-based electrode, the phenyl ether type membrane solvent, especially FPNPE is superior to the diester type ones in Na+ selectivity against K+. On the contrary, in the Na+ electrode of (B), de-tert-butylated derivative of (A), the diester type solvent, DOP gave good result. The selectivity coefficients for Na+ with respect to K+ (-log kPotNaK) being nearly 2.5. The (B)/DOP-based Na+-selective electrode was successfully applied to Na+ assay in human blood sera.

Silver Ion-Selective Polymeric Membrane Electrode Based on Lipophilic Monothiacrown Ether

Dodecyl-monothia-16-crown-5, which contains one sulfur and four oxygen atoms, was synthesized and tested for its usefulness as a neutral carrier for Ag+-selective polymeric membrane electrodes. Employment of a Ag+-complex of the thiacrown ether as the membrane active material instead of the thiacrown ether itself allowed the better potential response. The resulted ion selective electrodes exhibited Nernstian response to Ag+ in a wide activity range. The ion selectivities against alkali, alkaline-earth, and heavy metal ions, NH4+, and H+ were quite excellent. Silver ion in artificial samples was successfully determined by Ag+ potentiometric titration and Gran′s plot method with the Ag+ electrode.

Lithium ion selective electrodes based on crown ethers for serum lithium assay.

Previous Li/sup +/-selective polymeric membrane electrodes based on 14-crown-4 derivative 1 have been improved in the Li/sup +/ selectivities against Na/sup +/ and K/sup +/ by using 2 and 3 as the neutral carrier. Examination of the membrane solvents for the electrodes allowed further enhancement in the Li/sup +/ selectivities. An excellent k/sub LiNa//sup Pot/ value of 1.3 x 10/sup -3/ was attained with the poly(vinyl chloride) membrane containing 2 as the neutral carrier and o-nitrophenyl phenyl ether/tris(2-ethylhexyl) phosphate (98/2) as the solvent. Serum Li/sup +/ assay was successfully achieved with an electrode containing a combination of the optimized membrane based on the crown ether and a dialysis membrane, which eliminated interference by proteins in the samples.

Preparation and Response Properties of Selective Bio-Electrodes Utilizing Polymer Membrane Electrode-Based Ammonia Gas Sensors

Abstract A new type of potentiometric ammonia gas sensor is employed in the preparation of selective bio-electrodes for urea and glutamine. The bio-electrodes are constructed by immobilizing the enzyme urease and intact porcine kidney cells, respectively, at the surface of a disposable ammonium selective polymer membrane electrode-based ammonia gas sensor. The resulting electrodes have favorable response properties when compared to corresponding devices previously assembled with costly commercial gas sensors. Preliminary studies with the urea electrode demonstrate its usefulness for the rapid determination of urea in serum samples.