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  • 1
    Electronic Resource
    Electronic Resource
    Polymer membrane-based polyion sensors: Development, response mechanism, and bioanalytical applications (1995)
    Weinheim : Wiley-Blackwell
    Electroanalysis 7 (1995), S. 823-829 
    Details
    ISSN: 1040-0397
    Keywords: Polyion sensors ; Heparin ; Potentiometry ; Ion-selective electrodes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polymer membrane type ion-selective electrodes (ISEs) are now used routinely to measure clinically important ions (e.g., Na+, K+, Ca2+) in undiluted blood. However, efforts to develop similar sensors suitable for the direct detection of larger biomolecules have been less successful owing to the difficulty in identifying appropriate membrane chemistries that yield a significant and selective response toward the desired macromolecular analytes. Recently, we have found that poorly plasticized polymer membranes (PVC) doped with lipophilic anion and cation exchangers exhibit unexpectedly large and reproducible potentiometric responses to low levels (〈 1 μM) of certain biomedically important macromolecular polyionic species (heparin and protamine). This article provides data demonstrating how the specific membrane formulation and electrode geometry used influence the magnitude of the polyion EMF responses observed. The results suggest a non- equilibrium/steady-state polyion extraction process is responsible for the potentiometric heparin and protamine responses exhibited by appropriately formulated membranes. The practical utility of these sensors for monitoring heparin levels in blood as well as heparin/ protamine binding to other biologically important macromolecules will be described. Further, the prospects of adapting the same polyion extraction chemistry to devise optically sensitive thin polymer films for monitoring heparin will also be addressed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140070907
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of photopolymerized decyl methacrylate as a membrane matrix for ion-selective electrodes (1996)
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 1095-1100 
    Details
    ISSN: 1040-0397
    Keywords: Decyl methacrylate ; Photopolymerization ; Ion-selective electrodes ; Potentiometry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Potentiometric ion-selective sensors based on photopolymerized thin films of decyl methacrylate (DMA) crosslinked with hexanedioldimethacrylate (HDDMA) are described. The electrochemical response characteristics including slopes, selectivities, resistances and response times of several DMA-based ion-selective electrodes are reported and compared to those obtained using PVC-based sensors. Sensors incorporating the nonspecific anion exchanger tridodecylmethylammonium chloride and the plasticizer dioctyl sebacate exhibit a Nernstian response to chloride with the expected Hofmeister selectivity pattern. Additional response data for potassium and carbonate selective sensors prepared with the electrically neutral ionophores valinomycin and p-decyltrifluoroacetophenone, respectively, are also presented. The eflects of endogenous anionic sites arising from dissociated methacrylic acid impurities within the membrane matrix are discussed. The degree of site dissociation and its resulting contributions to the EMF response-governing equilibria are considered in detail. It is shown that such sites must be electrically compensated (via addition of adequate lipophilic cationic sites) when preparing neutral- carrier based anion sensors but otherwise have no apparent effect on the sensing membranes' selectivity and performance.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140081204
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  • 3
    Electronic Resource
    Electronic Resource
    Polyion-sensitive membrane electrodes for detecting phosphate-rich biological polyanions (1997)
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 1325-1330 
    Details
    ISSN: 1040-0397
    Keywords: Phosphated polyanions ; Potentiometry ; Ion-selective electrodes ; Polyanion-sensitive electrodes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Appropriately formulated polymeric membrane electrodes are shown to exhibit analytically useful nonequilibrium potentiometric responses to biologically important polyanions with high phosphate content, including polyphosphates and nucleic acids, in the μg/mL concentration range This response is dependent on the charge density, lipophilicity, and molecular weight of the polyanion species. The application of these electrodes for monitoring enzymatic activities is also demonstrated, using acid phosphatase/polyphosphate as a model system. The detection limit of this assay was found to be 0.9 ± 0.4 mU/mL with a linear range of 5-100 mU/mL. A similar electrochemical assay scheme can be utilized to monitor ribonuclease activity, using a RNA homopolymer as the substrate.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140091705
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