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  • 1
    Electronic Resource
    Electronic Resource
    Indirect electrochemical determination of L-tyrosine using mushroom tyrosinase in solution (1991)
    s.l. : American Chemical Society
    Analytical chemistry 63 (1991), S. 2762-2765 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00023a018
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    FIA-Fluorimetric assembly for the determination of noradrenaline hydrochloride by a solid-phase reactor with immobilized hexacyanoferrate(III) (1997)
    Springer
    Microchimica acta 126 (1997), S. 69-72 
    Details
    ISSN: 1436-5073
    Keywords: noradrenaline hydrochloride ; FIA ; solid-phase reactor ; fluorimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An FIA assembly provided with immobilized hexacyanoferrate(III) is proposed for the fluorimetric determination of noradrenaline hydrochloride. The oxidative reagent is immobilized by means of a strong anion-exchange resin. The FIA manifold is very simple and the calibration graph is linear over the range 0.5–75mgl−1 noradrenaline hydrochloride with an r.s.d of 0.88% (17 replicates) and a sample throughput of 84h−1. Foreign compounds such as NaCl, sucrose, lactose and sodium sulfate caused no significant errors. The procedure is applied to the determination of noradrenaline in a medicinal formulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01242663
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    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
    Keywords: Peptide nucleic acid ; Adsorption ; DNA biosensors ; Carbon paste electrodes ; Stripping potentiometry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140090206
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Electrochemical quantification of phenol using mushroom tyrosinase: Determination of the kinetic parameters of the enzyme (1994)
    Weinheim : Wiley-Blackwell
    Electroanalysis 6 (1994), S. 1136-1140 
    Details
    ISSN: 1040-0397
    Keywords: Phenol ; Biosensor ; Tyrosinase ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article presents a sensitive electroanalytical method for the determination of phenol in the presence of mushroom tyrosinase as well as a simple methodology to evaluate the kinetic parameters of this enzyme. The quantification is performed at low potential from the oxidation current of pyrocatechol that is formed by the action of mushroom tyrosinase in air-saturated solutions. Any electrochemically activated glassy carbon electrode is used. The course of the reaction is followed by cyclic voltammetry. A linear relationship holds up to 9.0 × 10-5 M, a detection limit is 4.6 × 10-7 M with a precision of 3.2% and a correlation coefficient of 0.997. Kinetic parameters evaluated from the same experiments are Vmax = 0.005 μmol of pyrocatechol produced per minute and KM = 2.0 × 10-4 M.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140061137
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  • 5
    Electronic Resource
    Electronic Resource
    Iridium-dispersed carbon paste enzyme electrodes (1996)
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 434-437 
    Details
    ISSN: 1040-0397
    Keywords: Enzyme electrodes ; Metallized carbon ; Iridium ; Glucose ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An highly selective first-generation glucose biosensor, based on an iridium-dispersed carbon-paste transducer, is described. The iridium-on-carbon particles provide excellent electrocatalysis for both the reduction and oxidation of hydrogen peroxide. Such unique catalytic action offers convenient biosensing of glucose at very low operating potentials, where interfering reactions are negligible. Factors influencing the electrocatalytic and biocatalytic actions are elucidated, along with the analytical performance. Implications to other oxidase-based amperometric electrodes are discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140080506
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Trace measurements of insulin by potentiometric stripping analysis at carbon paste electrodes (1996)
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 902-906 
    Details
    ISSN: 1040-0397
    Keywords: Insulin ; Myoglobin ; Protein ; Potentiometric stripping analysis ; Carbon paste electrode ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A potentiometric stripping method for trace measurements of insulin at carbon paste electrodes is described. The method is based on the controlled adsorptive accumulation of this polypeptide hormone at the anodically pretreated carbon surface followed by constant-current chronopotentiometric measurements of the surface species. A well-defined peak, associated with the oxidation of the tyrosine residues, is observed over the flat baseline of the potentiometric stripping operation. Variables of the pretreatment and measurement steps are optimized to offer a detection limit of 2 × 10-9M after 5 min preconcentration. Excess of nunierous potential interferences does not influence the response observed after transferring the electrode (with the accumulated insulin) to a blank electrolyte solution. A similar protocol is described for trace measurements of the protein myoglobin.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140081010
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Evaluation of different carbon electrodes for adsorptive stripping analysis of nucleic acids (1996)
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 753-758 
    Details
    ISSN: 1040-0397
    Keywords: Nucleic acids ; DNA ; RNA ; Nucleic acid oxidation ; Carbon electrodes ; Potentiomelric stripping analysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recently we have shown (see Ref. [8]) that submicrogram amounts of nucleic acids can be measured by potentiometric stripping analysis (PSA) at carbon paste electrodes. In this article we investigate and compare various carbon electrode materials for use in stripping analysis of nucleic acids. Both the interfacial and redox properties of DNA and RNA are strongly dependent upon the nature of the carbon material and the electrode pretreatment step. In view of the high solvent decomposition background response near the guanine oxidation peak, only potentiometric stripping analysis can be used for convenient quantitation of trace levels (ng/mL) of nucleic acids. The trend in sensitivity: carbon paste 〉 pyrolytic graphite 〉 highly oriented pyrolytic graphite 〉 carbon strip [with detection limits for oligo(dG)20 of 20, 30, 40 and 50 ng/mL, respectively, using 5 min accumulation]. No response was observed for trace measurements at the glassy carbon or carbon fiber electrodes. The influence of the surface pretreatment and accumulation time is described along with the analytical-performance characteristics at each electrode. Useful information about the adsorption behavior of nucleic acids at different carbon electrodes are also obtained.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140080809
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Screen-printed electrochemical hybridization biosensor for the detection of DNA sequences from the Escherichia coli pathogen (1997)
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 395-398 
    Details
    ISSN: 1040-0397
    Keywords: DNA biosensor ; Escherichia coli ; Bacteria ; Water quality ; Sequence-specific detection ; Hybridization ; Environmental monitoring ; Screen-printed electrode ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An electrochemical biosensor for the specific detection of short DNA sequences from the E. coli pathogen is described. This hybridization device relies on the immobilization of a 25-mer oligonucleotide probe, from the E. coli lacZ gene, onto a screen-printed carbon electrode. Chronopotentiometric detection of the Co(bpy)3+3 indicator is used for monitoring the hybridization event. Numerous variables of the assay protocol, including those of the probe immobilization step, the hybridization event, and the indicator association/detection, are characterized and optimized. Hybridization times of 2- and 30-min are sufficient for detecting 300- and 50 ng/mL, respectively, of the E. coli DNA target. Applicability to analysis of untreated environmental water samples is illustrated. Such single-use electrochemical sensors hold great promise for decentralized environmental and food testing for the E. coli pathogen.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140090508
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