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  • 1
    Electronic Resource
    Electronic Resource
    Multicomponent determinations by a membrane-discriminated gas phase analyzer and successive regression in the fiduciary region (1989)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 3 (1989), S. 601-608 
    Details
    ISSN: 0886-9383
    Keywords: Gas phase flow injection analysis ; Membrane-differentiated analysis ; Multicomponent determinations ; Successive linear regression ; Successive regression in fiduciary region ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A membrane-discriminated gas phase analyzer is proposed for multicomponent determinations. Nitrogen gas flows countercurrent through outer and inner channels in a tube-in-tube arrangement. The only communication between the two channels occurs through a 500 μm aperture covered by a porous PTFE membrane. A mixture of organic compounds (up to four components) is injected into the inner channel by a heated backflushed injector and the sample components diffusing into the outer channel are monitored by a flame ionization detector (FID). A calibration set, consisting of pure components, binary, ternary and quaternary mixtures (a total of 64 samples), provides the known data base: temporal profiles of the FID output as a function of sample composition. Although the overall response behavior is not a linearly additive function of individual analyte concentrations, the use of successive inverse multiple linear regression (while continually altering the choice of the calibration samples considered for the forward regression, on the basis of the most recent values of the predicted unknown sample composition) is shown to yield analytical results for unknown samples that are in good agreement with their true values.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180030408
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Fast voltammetric sensors for the measurement of soil water activity (1995)
    Weinheim : Wiley-Blackwell
    Electroanalysis 7 (1995), S. 626-632 
    Details
    ISSN: 1040-0397
    Keywords: Water sensor ; Soil ; Moisture ; Modified electrode ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Small inexpensive soil water sensors and the necessary electronics package for fast voltammetry (l04 V/s scan rate) are described. The sensor consists of a blunt ended hypodermic needle cathode containing a concentric PTFE insulating tube and therein, a Pt-wire anode. The sensing film is formed by dip-coating a 1:7 blend of a perfluorosulfonate and a polyestersulfonate polymer at the tip of the needle. Atop this sensing film is a composite protective film of cellulose acetate and nylon that inhibits the passage of ionic or low MW constituents and allows the transport of water. The sensor is sheathed in a PTFE tube that protrudes beyond the sensor tip and the protrusion gap is filled with a paste of talc and BaSO4 which serves as a water conduit between the soil and the sensor proper. The sensor is capable of making reliable moisture measurements between the wilting point and the field capacity of the soil sample; the response behavior consists of the combination of two nearly linear segments, the sensor output increasing steeply between the wilting point and ca. 60% of the field capacity and then much more gradually to the field capacity. The sensors have been field tested. No effect on sensor performance is observed even after burial under soil for several months.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140070705
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of alternating electric fields on transport through ion exchange membranes (1991)
    Weinheim : Wiley-Blackwell
    Electroanalysis 3 (1991), S. 783-792 
    Details
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transport of permitted and Donnas-forbidden ions as well as neutral solutes through ion exchange membranes have been investigated in continuous flow-through configurations in the presence and absence of an alternating electrical field (0.05-100 kHz, 0-40 V p-p). There is no discernible effect on the transport rate of forbidden ions and neutral solutes but very significant increases in steady state transmembrane transport occur for permitted ions. At least for cation exchangers, an increase in effective ion exchange capacity also appears to occur in the presence of the field. These effects are ascribed to the greater kinetic energy of the ions exposed to the alternating field and thus to the higher effective thermodynamic temperature the ions experience.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140030811
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Electrochemical sensing of gases based on liquid collection interfaces (1997)
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 585-591 
    Details
    ISSN: 1040-0397
    Keywords: Gas sensor ; Liquid collection ; Electrochemical sensing ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Although many electrochemical gas sensors have been reported, electrochemical gas sensors based on liquid collection constitute a smaller subset. Minimally, a liquid interface based electrochemical gas sensor is composed of two electrodes and an ion conducting electrolyte. There is a large number of possible arrangements of these parts, and many choices exist for their composition and preparation methods. This results in a diverse and rich technology now available for gas sensing. The measurement of some analyte gases of interest, notably ozone, nitrogen oxides, hydrogen peroxide, formaldehyde, ammonia, sulfur dioxide and hydrogen sulfide are specifically discussed. Finally, the recent reviews that are likely to be the most relevant to the further development of electrochemical detection approaches for gases with a liquid collection interface are cited and discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140090802
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    Paper (German National Licenses)
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