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  • Articles: DFG German National Licenses  (17)
  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 323 (1986), S. 464-468 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary A differential pulse polarographic method for the determination of iron employing the catalytic maximum wave has been studied. A well-defined differential pulse polarographic peak for iron(III) in Britton-Robinson buffer solution containing 50 μmol/l N-(2-hydroxyethyl) ethylenediamine N,N′,N′-triacetic acid (HEDTA) and 5 mmol/l KBrO3 is observed in the potential range from +0.2 to −0.3 V vs. SCE. The peak current is very large compared to that of the Fe(III)/EDTA complex, being proportional to the concentration of iron(III) between 1.00×10−8 and 3.58×10−6 mol/l under optimum conditions. The relative standard deviations for 3.58×10−7 mol/l and 1.79×10−6 mol/l iron(III) were 1.38 and 0.54%, respectively (n=5), and the calculated detection limit was 5.2×10−9 mol/l iron(III). The method has been applied to the determination of iron in fresh snow and rain waters.
    Notes: Zusammenfassung Das Verfahren beruht auf der Tatsache, daß in Britton-Robinson-Puffer (mit 50 μmol/l HEDTA und 5 mmol/l KBrO3) im Potentialbereich von +0,2 bis −0,3 V gegen SKE ein gut definierter puls-polarographischer Peak für Eisen(III) auftritt. Der Peakstrom ist im Vergleich zu dem des Fe(III)/EDTA-Komplexes sehr groß und ist unter optimalen Bedingungen im Konzentrationsbereich von 1,00·10−8 bis 3,58·10−6 mol/l der Eisen(III)-Konzentration proportional. Die relative Standardabweichung beträgt 1,38% bzw. 0,54% (n=5) für 3,58·10−7 mol/l bzw. 1,79·10−6 mol/l Fe(III). Die berechnete Nachweisgrenze liegt bei 5,2·10−9 mol/l Fe(III). Das Verfahren wurde zur Eisenbestimmung in Schnee- und Regenwasser eingesetzt.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 326 (1987), S. 214-217 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary The evaluation of dispersion in a FIA system, which is one of the indices of analytical sensitivity and separation, has been studied with an electrochemical detector and personal computer. Two different modes are applied to evaluate the degree of dispersion. One is a flat portion type mode, the other a hanging bell type mode. From these experiments it is possible to easily estimate the degree of dispersion in a FIA system concerning low dispersion (1 〈 D 〈 3) and medium dispersion (3 〈 D 〈 10), as discussed by Ruzicka and Hansen. Two regulation methods for sample volume in a FIA system are also discussed.
    Notes: Zusammenfassung Die Dispersion in einem Fließinjektionssystem, die für die analytische Empfindlichkeit und Trennung von Bedeutung ist, wurde nach zwei verschiedenen Methoden ausgewertet. Es ergab sich, daß der Dispersionsgrad im niederen (1 〈 D 〈 3) und mittleren Bereich (3 〈 D 〈 10) (entsprechend den Untersuchungen von Ruzicka und Hansen) leicht berechnet werden kann. Zwei verschiedene Regulierungsmethoden für das Probevolumen in einem FIA-System werden ebenfalls diskutiert.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 322 (1985), S. 486-490 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary A differential pulse-polarographic method has been studied for the determination of vanadium employing the catalytic maximum wave. A well-defined differential pulse polarographic peak is observed in the potential range from −0.2 to −0.7 V vs. SCE for vanadium(V) in 10 mmol 1−1 NaCl containing 10 mmol 1−1 acetic acid, 40 mmol 1−1 pyrocatechol, and 2.5 mmol 1−1 KBrO3. The peak current is very large and proportional to the concentration of vanadium(V) between 1×10−7 and 1×10−6 mol 1−1. The relative standard deviation at 0.5 μmol l−1 vanadium(V) was 2.06% (n=7). This method has been successfully applied to the determination of vanadium in standard materials such as pond sediment.
    Notes: Zusammenfassung Ein gut definierter differentialpuls-polarographischer Peak wurde für Vanadium(V) in 10 mmol/l NaCl-Lösung, die 10 mmol/l Essigsäure, 40 mmol/l Brenzcatechin und 2,5 mmol/l KBrO3 enthielt, beobachtet (Potentialbereich −0,2 bis −0,7 V gegen SCE). Der Peakstrom ist sehr groß und die Vanadiumkonzentration im Bereich von 1×10−7 bis 1×10−6 mol/l proportional. Die relative Standardabweichung betrug 2,06% (n=7) bei 0,5 μmol/l Vanadium(V). Das Verfahren wurde mit gutem Erfolg zur Vanadiumbestimmung in Standardproben (z.B. Teichsediment) eingesetzt.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 347 (1993), S. 368-370 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method is described for the determination of citrate lyase (E.C. 4.1.3.6) activity using differential pulse polarography. It is based on the measurement of the reduction wave of the reaction product pyruvate in the presence of an excess of citrate as the substrate. The method is very sensitive and rapid. Additionally, kinetic parameters and the Michaelis constant (Km) can be obtained.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 333 (1989), S. 19-22 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An electrochemical method for the specific determination of citric acid in sports drink and plaster using citrate lyase and oxaloacetate decarboxylase has been studied. The technique is reasonably rapid and simple to perform. Results from recovery experiments are excellent, i.e. recovery is 99.7±3.0% at a confidence limit of 95% (n=3), and reproducibility (R.S.D.) at 20 μmol/l citric acid is 1.46% (n=3). The method can possibly be used for monitoring citric acid in clinical and food-processing samples.
    Type of Medium: Electronic Resource
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  • 16
    ISSN: 1040-0397
    Keywords: Organogermanium ; Voltammetry ; Polarography ; Reduction mechanism ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article describes the electrochemical behavior of β-carboxyethylgermanium sesquioxide (Ge-132) on mercury electrodes in weakly acidic solution. The Ge-132 exhibits two Well-defined cathodic waves in linear-sweep voltammetry and polarography. The first wave in a voltammiogram of Ge-132 is a simple two-electron reduction and exhibits the property of adsorption. From chronoamperometry, the reaction in die second wave, however, proves to be an ECE mechanism and ultimately yields metallic germanium and propionic acid. The determination of small amounts of Ge-132 is investigated by differential pulse polarography in an acetate buffer. The detection limits of Ge-132 are below 0.2 μmol dm-3.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electroanalysis 4 (1992), S. 801-803 
    ISSN: 1040-0397
    Keywords: Citrate ; biosensor ; mercury film electrode ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe a new amperometric biosensor which is constructed from a mercury film electrode and an enzyme-immobilized membrane. This biosensor is based on detecting the reduction current of an organic acid produced by enzyme reactions. The detection range of this biosensor was 5.0 × 10-4 - 3.0 × 10-3 M and relative standard deviation, R.S.D. at 1.0 × 10-3 M was 4.8%.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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