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  • 05. General::05.03. Educational, History of Science, Public Issues::05.03.99. General or miscellaneous
  • 05. General::05.09. Miscellaneous::05.09.99. General or miscellaneous
  • Additives
  • Wiley-Blackwell  (6)
  • American Chemical Society
  • Giunti Progetti Educativi
  • 1995-1999  (6)
Collection
Keywords
Publisher
  • Wiley-Blackwell  (6)
  • American Chemical Society
  • Giunti Progetti Educativi
  • Springer  (1)
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    An original electroenzymatic system: Flavin reductase-riboflavin for the improvement of dehydrogenase-based biosensors. Application to the amperometric detection of lactate (1997)
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 685-688 
    Details
    ISSN: 1040-0397
    Keywords: Flavin reductase ; Polypyrrole ; Biosensor ; Dehydrogenase ; Lactate ; Additives ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electropolymerization of a flavin reductase (Fre) - amphiphilic pyrrole ammonium mixture previously adsorbed on the electrode surface provides an efficient bioelectrode for the amperometric detection of NADH and NADPH. The bioelectrode response was based on the oxidation at -;0.1 V vs. SCE of the enzymically generated dihydroriboflavin. The sensitivity and detection limit of the bioelectrode were 29 mAM-1 cm-2 and 0.2 μM for NADH and 15.8 mAM-1 cm-2 and 0.4 μM for NADPH. The coimmobilization of Fre and a lactate dehydrogenase leads to a dehydrogenase-based bioelectrode for the determination of lactate in the presence of riboflavin and NAD+. With laponite additives into the polypyrrole host matrix, the sensitivity and the detection limit of the bioelectrode for lactate are 11.7 mAM-1 cm-2 and 1 μM respectively. Owing to the negative value of the applied potential for the oxidation of riboflavin, the response of the bienzyme electrode remains insensitive to interferents like ascorbate, urate and acetaminophen.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140090906
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  • 2
    Electronic Resource
    Electronic Resource
    Quantitative description of migration behavior of porphyrins based on the dynamic complexation model in a nonaqueous capillary electrophoresis system (1997)
    Weinheim : Wiley-Blackwell
    Electrophoresis 18 (1997), S. 82-91 
    Details
    ISSN: 0173-0835
    Keywords: Nonaqueous capillary electrophoresis ; Dynamic complexation ; Porphyrin ; Additives ; Separation theory ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The effect of an additive (Brij 35) on the mobilities of a group of porphyrin acids is quantitatively characterized based on a 1:1 dynamic complexation model. Varying additive concentration shifts the equilibrium and changes the viscosity of the background electrolyte. The equilibrium constant, the electrophoretic mobility of the free analyte, and the electrophoretic mobility of the complex are identified as the parameters necessary to describe the analytes' migration behavior. Several statistical methods for obtaining these parameters are discussed. The equilibrium constants and complex mobilities are calculated using three different linear regression methods. The weighted y-reciprocal method was preferred because it gives smaller error, and the data points are evenly distributed along the concentration axis. These values are confirmed using a nonlinear regression to ensure that the proper weighting was used in the linear regression plots. The parameters are then used to predict the apparent mobilities of the analytes over the entire additive concentration range, allowing the optimum separation conditions to be identified. For disclike molecules, such as porphyrins, the mobility is determined by the orientation of the molecule in an electric field, in addition to their size and charge. The strength of binding between the porphyrins and Brij 35 depends on the number of binding sites and the solvation shell.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150180117
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  • 3
    Electronic Resource
    Electronic Resource
    Size-based separation of polyelectrolytes by capillary zone electrophoresis: Migration regimes and selectivity of poly(styrenesulphonates) in solutions of derivatized cellulose (1997)
    Weinheim : Wiley-Blackwell
    Electrophoresis 18 (1997), S. 98-103 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Linear polymers ; Polyelectrolytes ; Entanglement ; Physical network ; Additives ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The migration regimes and the separation selectivity of linear poly(styrenesulfonates) (PSS) were investigated in solutions of linear polymeric hydroxyethylcellulose (HEC). Variable parameters were the number of PSS monomer units (in the range of 25-6520), HEC concentration (below and above the entanglement threshold), molecular mass of HEC (between 35900 and 438000 Da) and electric field strength (from 190 to 1140 V/cm). Besides those regimes which are known for migration of polyelectrolytes in physical networks (Ogston sieving, reptation without and with orientation), the observed separation below the entanglement threshold indicates an effect of solute-chain interactions similar to that observed for the separation of double-stranded DNA. From the dependence of the separation selectivity on HEC concentration and molecular weight it was found that both parameters increase the separation. The selectivity of the solutions of higher concentrated low molecular HEC was compared to lower concentrated high molecular HEC, which has a similar bulk viscosity, and therefore obeys comparable peak dispersion due to thermal broadening. At high field strengths (preferably used in capillary electrophoresis) the former gave better separation only for shorter PSS molecules. For separation of longer PSS molecules, only high molecular HEC is applicable due to the deformation of the low molecular matrix by large analyte molecules.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150180119
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  • 4
    Electronic Resource
    Electronic Resource
    Quantitative description of analyte migration behavior based on dynamic complexation in capillary electrophoresis with one or more additives (1997)
    Weinheim : Wiley-Blackwell
    Electrophoresis 18 (1997), S. 706-716 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Dynamic complexation ; Analyte migration behavior ; Additives ; Viscosity correction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: A comprehensive theory is proposed to describe the migration behavior of analytes in capillary electrophoresis (CE) when one or more additives are present in the buffer solution. This theory amalgamates and extends the previous work done by others. The capacity factor (ḱ) in this theory is defined as the product of the equilibrium constant and the additive concentration, thus, ḱ changes linearly with additive concentration. The net electrophoretic mobility of an analyte is a function of ḱ, therefore, it can be changed by varying the additive concentration. Three parameters are needed to predict the mobility of an analyte in a one-additive CE system: the mobility of the free analyte, the mobility of the complex, and the equilibrium constant for the analyte-additive interaction (which determines the fraction of the free analyte at different additive concentrations). When additives are used, the change in viscosity obscures this relationship, therefore, a viscosity correction factor is required to convert all mobilities to an ideal state where the viscosity remains constant. The migration behavior of an analyte in a solution with multiple additives can be predicted and controlled, once the equilibrium constants of the interactions between the analyte and each of the additives are obtained separately. β-Cyclodextrin and hydroxypropyl-β-cyclodextrin are used as additives and the migration behavior of phenol, p-nitrophenol, and benzoic acid are studied as a model system to verify this theory. When the necessary viscosity correction factor is included, the net electrophoretic mobilities of the analytes obtained from experimental results agree with the values predicted by the theory based on dynamic complexation. Although only experiments with one and two additives were carried out to verify the theory, the equations apply to situations when more than two additives are used. The relationship between the theories of electrophoresis and chromatography is clarified.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150180509
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  • 5
    Electronic Resource
    Electronic Resource
    Analysis of ε-N-2-furoylmethyl-L-lysine (furosine) in dried milk by capillary electrophoresis with controlled electroosmotic flow using N,N,N′,N′-tetramethyl-1,3-butanediamine in the running electrolyte solution (1996)
    Weinheim : Wiley-Blackwell
    Electrophoresis 17 (1996), S. 120-124 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Furosine ; Food analysis ; Additives ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The electrophoresis of ε-N-2-furoylmethyl-L-lysine (furosine) was studied in an attempt to develop a method for the identification and quantitation of this compound in processed food. The effect of pH and composition of electrolyte solution on both the electrophoretic migration of furosine and the electroosmotic flow in a bare fused-silica capillary of 75 μm internal diameter was investigated. We demonstrate that the addition, to the running electrolyte solution, of N,N,N′,N′-tetramethyl-1,3-butanediamine (TMBD) at concentrations ranging from 20 to 80 mM improves peak efficiency and can be used to modulate the migration time of furosine by controlling the electroosmotic flow which is reversed from cathodic to anodic. In a sample of dried milk subjected to a long period of storage under controlled conditions, furosine could be efficiently and reproducibly separated and quantitated by employing as the running electrolyte 60 mM TMBD titrated to pH 2.5. Capillary electrophoresis is a promising technique for the rapid identification and quantitation of furosine in processed food.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150170120
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  • 6
    Electronic Resource
    Electronic Resource
    N,N,N′,N′-Tetramethyl-1,3-butanediamine as effective running electrolyte additive for efficient electrophoretic separation of basic proteins in bare fused-silica capillaries (1995)
    Weinheim : Wiley-Blackwell
    Electrophoresis 16 (1995), S. 630-635 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Proteins ; Additives ; Electroosmotic flow ; N,N,N′,N′-tetramethyl-1,3-butanediamine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The effect of N,N,N′,N′-tetramethyl-1,3-butanediamine (TMBD) in the running electrolyte on the electroosmotic flow and the migration behavior of four standard basic proteins in bare fused-silica capillaries was examined at pH 4.0, 5.5, and 6.5. Depending on the electrolyte pH and additive concentration the electroosmotic flow was either cathodic or anodic. A similar Langmuirian-type dependence of the electroosmotic flow on the concentration of TMBD in the running electrolyte was found at the three experimented pH values, which may be indicative of the specific adsorption of the additive in the immobilized region of the electric double layer at the interface between the capillary wall and the electrolyte solution. Electrophoretic separations of the four standard basic proteins performed at the three above pH values, showed well-resolved, efficient and symmetric peaks, demonstrating the utility of this additive for protein electrophoresis in bare fused-silica capillaries. The variations in separation efficiency, peak capacity, resolution and reproducibility of migration times as a function of the additive concentration at pH 6.5 were also examined.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.11501601101
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