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  • 1
    Digitale Medien
    Digitale Medien
    Trace Measurements of RNA by Potentiometric Stripping Analysis at Carbon Paste Electrodes (1995)
    s.l. : American Chemical Society
    Analytical chemistry 67 (1995), S. 4065-4070 
    Details
    ISSN: 1520-6882
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ac00118a006
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  • 2
    Digitale Medien
    Digitale Medien
    Stripping voltammetric determination of trace amounts of mercury using a carbon paste electrode modified with 2-mercapto-4(3H)-quinazolinone (1993)
    Springer
    Microchimica acta 112 (1993), S. 135-146 
    Details
    ISSN: 1436-5073
    Schlagwort(e): stripping voltammetry ; mercury ; carbon paste electrode ; 2-mercapto-4(3H)-quinazolinone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A carbon paste electrode modified with 2-mercapto-4(3H)-quinazolinone was used for the voltammetric determination of mercury(II). Mercury was preconcentrated onto the surface of the modified electrode only by the complexing effect of the modifier without application of potential (i.e. in open-circuit conditions). After exchange of the medium, the accumulated amount of mercury(II) was determined by differential pulse anodic stripping voltammetry. The response depended on the concentration of mercury in the bulk solution, preconcentration time, and other parameters. The detection limit was 0.1 μg 1–1 Hg(II) for a preconcentration time of 15 min. Preconcentration for suitable times yielded a linear calibration graph from 0.5 to 6000 μg 1–1 Hg(II). For multiple determinations (5 runs), the relative standard deviation was 5% for a concentration of 100 μg 1–1 Hg(II). The proposed procedure was used to determine trace mercury in plant and sewage sludge samples with good results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01243330
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  • 3
    Digitale Medien
    Digitale Medien
    Studies on the voltammetric behaviour of a 2-mercaptoimidazole containing carbon paste electrode: determination of traces of silver (1994)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 348 (1994), S. 736-741 
    Details
    ISSN: 1618-2650
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The voltammetric behaviour of a 2-mercaptoimidazole (2-MI) containing carbon paste electrode was studied. When mixed to carbon paste as an electrode modifier, 2-MI can be reduced at negative potentials (−1 V vs. SCE), but it does not give a response in the potential range where Ag(0) is oxidized to Ag(I). Silver could be accumulated from 0.1 mol l−1 acetate buffer onto a 2-MI modified carbon paste electrode without a potential applied; after medium exchange, it was reduced at −1 V vs. SCE in 0.1 mol l−1 acetate buffer solution and determined by differential pulse anodic stripping voltammetry. With suitable preconcentration times, the detection limit was 0.1 μg l−1; a linear relation between current and concentration was found to exist within a range of 0.5 to 1000 μg l−1. In the presence of EDTA, common metal ions have no or only little effect on the voltammetric determination of silver.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00323695
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  • 4
    Digitale Medien
    Digitale Medien
    Adsorption and detection of peptide nucleic acids at carbon paste eletrodes (1997)
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 120-124 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Peptide nucleic acid ; Adsorption ; DNA biosensors ; Carbon paste electrodes ; Stripping potentiometry ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Peptide nucleic acids (PNA) are new DNA analogs which offer great promise for highly specific DNA biosensors, for use as antisense drugs, or for various molecuilar biology applications. This article evaluates the interfacial behavior of PNA at carbon paste electrodes, in comparison to DNA. While both PNA oligomers display a strong adsorption onto the carbon surface, they differ intheir interfacial properties due to differences in change and structure. Factors influencing the adsorption behavior, including the adsorption potential or time, PNA concentration, coexisting anions and cations, or buffer concentration, are explored. The strong adsorption is exploited for an effective preconcentration step prior to the chronopotentiometric measurement. The resulting adsorptive stripping potentiometric protocol offers convenient quantitation of ng/mL levels of PNA, as desired for future diagnostic, pharmaceutical and biological applications of these DNA analogs.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140090206
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  • 5
    Digitale Medien
    Digitale Medien
    Insoluble inorganic salts as carbon paste electrode modifiers for preconcentration and voltammetric determination of oxalic acid (1995)
    Weinheim : Wiley-Blackwell
    Electroanalysis 7 (1995), S. 639-643 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Carbon paste electrodes ; Modifiers ; Inorganic salts ; Voltammetry ; Oxalic acid ; Lead sulfate ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A novel approach for chemical modification of carbon paste electrodes (CPEs) has been investigated. Selected water-insoluble inorganic salts as modifiers were found to exhibit preconcentration capability for oxalic acid under open-circuit conditions in a pH 4.3 buffered solution. After medium exchange to a pure electrolyte (Britton-Robinson buffer, pH 8), the accumulated oxalate was measured by square-wave anodic stripping voltammetry with a peak current response at 1.2 V (vs. Ag/AgCl). The water-insoluble inorganic salts as modifiers were active through the interfacial accumulation of insoluble oxalate by the exchange of anions. The candidate inorganic salts should be, therefore, less insoluble than the corresponding oxalates, whereas, the differences in solubility between the modifiers and the corresponding oxalates are of minor importance. Among the investigated inorganic salts, lead sulfate produced the highest response under the employed conditions and was therefore exploited as accumulating material for oxalic acid. With suitable preconcentration times, a linear calibration graph from 0.7 mg/L to 42.8 mg/L of oxalic acid in the analyte solution was obtained, and a detection limit of 0.3 mg/L at a preconcentration time of 5min was achieved. The lead sulfate-modified CPE was used to determine oxalic acid in orange juice without pre-separation.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140070707
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  • 6
    Digitale Medien
    Digitale Medien
    Metal-dispersed screen-printed carbon electrodes (1995)
    Weinheim : Wiley-Blackwell
    Electroanalysis 7 (1995), S. 1032-1034 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Screen printing technology ; Sensors ; Electrocatalysis ; Disposable electrodes ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Nickel-, cobalt-, copper-, and palladium-dispersed carbon inks are used for screen printing of electrocatalytic sensors. The resulting strips couple the advantages of mass-producible disposable electrodes and effective catalytic surfaces. The dispersed metal particles lead to a marked decrease in the oxidation potential for carbohydrates, amino acids, aldehydes or alcohols. Characterization of the electrocatalytic behavior and the analytical (sensing) performance are reported. Applicability to wine samples is illustrated.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140071107
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  • 7
    Digitale Medien
    Digitale Medien
    Studies on the electrocatalytic reduction of aliphatic aldehydes on palladium-modified carbon paste electrodes (1994)
    Weinheim : Wiley-Blackwell
    Electroanalysis 6 (1994), S. 397-404 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Aldehydes ; Electrocatolysis ; Modified electrodes ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Carbon paste electrodes modified either by mixing palladium powder to the electrode material or by electrodepositing Pd via cycling the potential between 0.4 and -0.7 V (versus SCE) exhibited stable electrocatalytic response for aliphatic aldehydes and aliphatic alcohols. The aldehydes (e.g., formaldehyde) could be reduced to the corresponding alcohols (e.g., methanol), and the alcohols (e.g., methanol) could be oxidized to the corresponding aldehydes (e.g., formaldehyde) by direct current voltammetry (DCV). The electrocatalytic effect was attributed to the electrogenerated metallic palladium at the electrode surface. The cathodic current peak, the height of which was proportional to the aldehyde concentration, had negative values; it was ascribed to a desorption of the product of the electrode reaction from the surface of the electrode. This peak was used for quantitative analytical purposes.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140060507
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  • 8
    Digitale Medien
    Digitale Medien
    Synergistic electrochemical and chemical modification of carbon paste electrodes for open-circuit preconcentration and voltammetric determination of trace adenine (1995)
    Weinheim : Wiley-Blackwell
    Electroanalysis 7 (1995), S. 1126-1131 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Carbon paste electrodes ; Modified electrodes ; Synergism ; Voltammetry ; Adenine ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A new concept of electrode modification is presented, consisting of chemically assisted electrochemical oxidative pretreatment of the electrode surface. If carbon paste electrodes (CPEs) are polarized at +1.75 V (vs Ag/AgCl) in a dilute alkaline medium (1 × 10-3mol/L) containing 0.1 mol/L NaNO3 for 60s, they exhibit a unique ability to preconcentrate adenine, an important biological substance, that served as a model compound. In this work, a thorough study has been performed to explore the new pretreatment procedure, but also its analytical application for trace adenine determination was optimized. During the pretreatment of a CPE, a specific oxide layer is formed due to a synergistic effect of a combined anodic and chemical oxidation process, in which the presence of sodium nitrate plays a crucial role. In a subsequent step under open-circuit conditions, adenine is oxidized by the oxide layer, and the resulting oxidation product is strongly adsorbed onto the electrode surface. After medium exchange, the adsorbed oxidation product of adenine is reduced at -0.5 V (vs. Ag/AgCl) and the voltammetric current response can be utilized for analytical purposes. Applying 10 min accumulation and square-wave voltammetric operation, the detection limit of 20 μg/L (1.5 × 10-7 mol/L) of adenine in a sample solution was acquired. The voltammetric behavior of adenine at plain and pretreated CPEs is also presented and discussed.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140071206
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  • 9
    Digitale Medien
    Digitale Medien
    Electrocatalytic reduction of hydrogen peroxide on a palladium-modified carbon paste electrode (1995)
    Weinheim : Wiley-Blackwell
    Electroanalysis 7 (1995), S. 340-345 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Electrocatalysis ; Palladium ; Hydrogen peroxide ; Carbon paste electrode ; Voltammetry ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A palladium-dispersed carbon paste electrode was used for the electrocatalytic reduction of hydrogen peroxide. After cycling the potential between 0.4 and -0.8V (vs. SCE) in pure dilute alkaline solution (10-3M NaOH), the resulting electrode surface exhibited stable and sensitive electrocatalytic response for hydrogen peroxide. The involved catalytic mechanism was thoroughly investigated. The electrocatalytic effect was attributed to electrogenerated elemental palladium at the electrode surface. The catalytic reduction of hydrogen peroxide proceeds via the hydroxyl radical, OH·. Dissolved oxygen can also be catalytically reduced in a similar way to hydrogen peroxide. The height of the cathodic catalytic current peak, as obtained by linear sweep voltammetry (LSV) was directly proportional to the hydrogen peroxide concentration over a very wide concentration range (0.1-600mgL-1). The detection limit (3σ) was calculated as 50 μgL-1 H2O2.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140070407
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  • 10
    Digitale Medien
    Digitale Medien
    Voltammetric determination of nitrate with a modified carbon paste electrode (1994)
    Weinheim : Wiley-Blackwell
    Electroanalysis 6 (1994), S. 227-236 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Nitrate ; Carbon paste ; Modified electrodes catalysis ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A method for the voltammetric determination of nitrate in drinking water is presented. Nitrate exerts a catalytic effect on the reduction and reoxidation of thallium (1 ↔ 0) in cyclic and differential pulse voltammetry, leading to a peak enhancement. Nitrate can be preconcentrated together with tetrachlorothallate(III) from hydrochloric acid solutions onto a carbon paste electrode modified with a liquid anion exchanger. (Amberlite LA2) under open circuit conditions. After reduction of the Tl(III) to Tl(0) at the electrode surface at a potential of -1.2 V (vs. SCE), the increase of the reoxidation current of Tl(III) to TI(I) by nitrate is exploited for analytical purposes. Linearity between current and concentration exists for 0.5 to 60 μg · mL-1 nitrate when applying anodic differential pulse vokammetry. Mechanical regeneration of the electrode surface is necessary after each measurement. The interference of other anions and the influence of methodical parameters are invistigated. The applicability of this method for the determination of nitrate in drinking wat concise overview on the the electroanalytical techniques for the Quantitative determination of nitrate is also presented.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140060309
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