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  • 1
    Electronic Resource
    Electronic Resource
    Stripping voltammetry of copper and lead using gold electrodes modified with self-assembled monolayers (1997)
    Springer
    Journal of solid state electrochemistry 1 (1997), S. 241-247 
    Details
    ISSN: 1433-0768
    Keywords: Key words Underpotential deposition ; Stripping analysis ; Self-assembled monolayers ; Multiple stripping peaks ; Heavy metals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract One problem associated with using bare solid metal electrodes, such as gold and platinum, in stripping analysis to determine heavy metal ions such as lead and copper ions in dilute solutions is that underpotential deposition (UPD) gives multiple stripping peaks in the analysis of mixtures. These peaks are often overlapped and cannot be conveniently used for analytical purposes. Bifunctional alkylthiols, such as 3-mercaptopropionic acid, with an ionizable group on the other terminal end of the thiol can form self-assembled monolayers (SAMs) on the surface of the gold electrode. It is shown that such an SAM-modified gold electrode minimizes the UPD effects for the stripping analysis of lead and copper. The anodic peak potential shifts and the peak shape changes, indicating that the SAM changes the deposition and stripping steps of these heavy metal ions. Thus, the sensitivity levels for both single species and mixtures can be significantly improved for the conventional solid electrodes. The mechanism of the deposition reaction at the SAM-modified gold electrodes is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100080050055
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  • 2
    Electronic Resource
    Electronic Resource
    Blocking behavior of self-assembled monolayers on gold electrodes (1997)
    Springer
    Journal of solid state electrochemistry 1 (1997), S. 148-154 
    Details
    ISSN: 1433-0768
    Keywords: Key words Self-assembled monolayers ; Thiols ; Gold ; Electrode ; Adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Self-assembled monolayers (SAMs) with metal electrodes, especially thiols on gold, are the subject of this investigation because of the unique properties of SAM-modified surfaces. Normal alkanethiols are used to modify the surface of a conventional gold electrode to block certain ions such as Pb(II) and Cu(II) from the surface of the electrode. Normal alkanethiols are also used to study the SAM-gold interfacial adsorption-desorption behavior of the self-assembled monolayer. The effects of varying chain length of SAMs, varying concentration of the alkanethiol solutions, immersion time of the pure gold electrode in the SAM solution, and the stability of a SAM-modified gold electrode in fresh chloroform are investigated using the oxidation-reduction peaks of gold. Conditions that optimize the surface coverage and the uniformity of the SAMs have been determined. Normal alkanethiols proved to be a good insulator on the electrode surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100080050039
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  • 3
    Electronic Resource
    Electronic Resource
    Capillary enzyme immunoassay with electrochemical detection for determining indole-3-acetic acid in tomato embryos (1999)
    Springer
    Fresenius' journal of analytical chemistry 364 (1999), S. 170-174 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An amperometric immunoassay for indole-3-acetic acid (IAA) in tomato embryos was developed. The antibody against IAA was covalently bound to the chemically modified inner surface of a 22 μL silica capillary. The competitive binding of methylated IAA and an IAA alkaline phosphatase conjugate for a limited amount of antibody was accomplished in the silica capillary in 20 min. The enzymatic product p-aminophenol, produced from p-aminophenyl phosphate, was determined by flow injection analysis with amperometric detection. A detection limit for IAA of 3 pg/μL was obtained. The average concentration of IAA in mature embryos measured by this method is 0.37 ± 0.03 μg/g. Although isotope dilution GC-SIM-MS can achieve the same detection limit, the sample analysis is not feasible in such a complicated matrix and further purification and separation are required.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160051318
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  • 4
    Electronic Resource
    Electronic Resource
    Thiolato-technetium complexes. 4(1): Synthesis, characterization and electrochemical properties of bis(1,2-bis(dimethylphosphino)-ethane)technetium(III) complexes with arene-thiolato ligands (1993)
    Springer
    Transition metal chemistry 18 (1993), S. 209-217 
    Details
    ISSN: 1572-901X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The reaction of trans-[Tcv(OH)(O)(DMPE)2]2+ (DMPE = 1,2-bis(dimethylphosphino)ethane) with a series of arenethiols in base produces the novel complexes cis-[TcIII-(SC6H4X-p)2 (DMPE)2]+ for X = H, Cl, Me, OMe, t-Bu. One of the complexes has been characterized by X-ray crystallography: cis-[Tc(SPh)2(DMPE)2]PF6, chemical formula Tc1S2P5F6C24H42, crystallizes in the orthorhombic space group P21nb with Z = 4 and lattice parameters a = 9.311(1) Å, b=11.190(2) Å, c = 31.936(4) Å, Vol = 3327.3(8) Å3. The final weighted R-value was 0.033. Averaged structural parameters are Tc—S = 2.29(2) Å, Tc—P (trans to P) = 2.42(1) Å, Tc—P (trans to S) = 2.49(3) Å, Tc—S—C = 118.5(5)°. The complexes have been characterized by FAB mass spectrometry and u.v.-vis. spectroscopy. The visible region charge transfer bands are diagnostic for cis geometry in the [Tc(SR)2(DMPE)2]+ complexes. Electrochemical and spectroelectrochemical measurements show reversible TcIII/II redox couples in the range -0.19V to -0.38V versus Ag/AgCl (3 M NaCl). Irreversible couples are exhibited at ca. -1.1 V to -1.2 V for TcII/I and +0.7V to +0.9V for TcIV/III. Variation in redox potential is discussed in terms of sulphur nucleophilicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00139958
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of serum alkaline phosphatase activity by electrochemical detection with flow injection analysis (1993)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 346 (1993), S. 859-862 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In this enzyme assay for kinetic measurement of alkaline phosphatase (EC 3.1.3.1) activity in human serum by flow injection analysis with electrochemical detection (FIA-EC), the substrate phenyl phosphate is enzymatically hydrolyzed and the phenol produced is quantified by FIA-EC. The standard curve is linear over the range 40 to 500 U/l, and the predicted linearity is up to 1000 U/l. The CV is 5% over the range of the assay. Correlation with the Sclavo Diagnostics nitrophenyl phosphate spectrophotometric technique gave an r of 0.98. This new technique requires as little as 1 μl of serum. The FIA-EC method is not subject to interference by hemolysis, icteria, or lipemia or by electroactive substances such as urate, ascorbate, or acetaminophen. Sensitive measurements free from spectrophotometric interferences are thus possible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00321305
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  • 6
    Electronic Resource
    Electronic Resource
    Application of scanning electrochemical microscopy and scanning electron microscopy for the characterization of carbon-spray modified electrodes (1994)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 348 (1994), S. 712-718 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Different gold surfaces modified by carbon-spray have been investigated by scanning electron microscopy (SEM) and scanning electrochemical microscopy (SECM). A transformation of the SECM image to a distance-location profile is proposed which assists the correlation of both images. The structures found in the transformed SECM images of carbon-spray layers on gold substrates can be explained by the topographic features visible in the SEM pictures. Tempering the carbon spray results in an increased density of electrochemically reactive carbon particles which could be confirmed by cyclic voltammetric investigations. Gold minigrids modified with carbon spray expose some areas of especially large currents which could not be predicted from their SEM images. This effect may result from particles located at the edge of a wire intersection having relatively large active surfaces per particle. They contribute significantly to the total current of the minigrid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323691
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