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Oldřich Dracka - One of the best experts on this subject based on the ideXlab platform.

  • application of elimination voltammetry to adsorptive stripping of dna
    Electroanalysis, 2000
    Co-Authors: Libuse Trnkova, Rene Kizek, Oldřich Dracka
    Abstract:

    Adsorptive stripping voltammetry has been extended by elimination voltammetry with linear scan rate (EVLS). EVLS offers the elimination of selected currents from the linear scan voltammetry results. It can be achieved by an elimination function formed by a linear combination of total currents measured at different scan rates, because the basic idea of elimination of chosen currents (for example the charging current, I-c, the reversible current for Substances transported only by linear diffusion, I-r, and the purely kinetic current, I-k) consists of the different dependence of voltammetric current on the scan rare. In this article, the problem of Substance adsorption influence on the elimination voltammetry results has been studied. Theoretical curves of an irreversible current with Adsorbed Substance being electroactive were calculated for three elimination functions. A: the function eliminating I-k and I-c and conserving I-r B: the function eliminating I-c and I-r. conserving I-k; and C: the function eliminating I-r and I-k and conserving I-c, where I-c, I-r, and I-k are the charging current, the reversible diffusion current, and the kinetic current, respectively. A larger difference between diffusion and adsorption was exhibited by the elimination function A. It provides a substantial increase in resolution and sensitivity as compared to the linear scan voltammetry current peak and clearly marks the adsorption. In case of the adsorption of electroactive Substances this elimination function A can be useful for analytical applications, particularly for the adsorptive stripping voltammetry with electrochemical irreversible systems. As a practical application, the adsorptive stripping voltammetry of thermally denatured DNA on a hanging mercury electrode has been developed. While the LSV signal of single-stranded DNA at low concentrations gives a slight hint of the cathodic peak (due to the reduction of adenine and cytosine residues), the elimination A provides quite a clear signal in the form of the peak-counterpeak. It is possible to determinate DNA at concentrations below micrograms per milliliter by using this elimination function. The results received by the adsorptive stripping voltammetry in the mode of linear scan (LSV), square-wave (SWV) and elimination with linear scan (EVLS) are discussed.

  • application of elimination voltammetry to the electroanalysisof an Adsorbed Substance
    2000
    Co-Authors: Libuse Trnkova, Rene Kizek, Oldřich Dracka
    Abstract:

    In the elimination voltammetry with a linear scan rate (EVLS), elimination of the selected particular currents from the linear scan voltammetry results is achieved by an elimination function formed by a linear combination of the total currents measured at different scan rates.Theoretical curves of an irreversible current with Adsorbed Substance being electroactive were calculated for three elimination functions: A - the function eliminating Ik and Ic and conserving Ir , B - the function eliminating Ic and Ir , conserving Ik , and C - the function eliminating Ir and Ik and conserving Ic, where Ic , Ir , and Ik are the charging current, the reversible diffusion current, and the kinetic current, respectively. A larger difference between diffusion and adsorption was exhibited by the elimination function A. It provides a substantial increase in resolution and sensitivity as compared to the linear scan voltammetry current peak and clearly marks the adsorption.

Libuse Trnkova - One of the best experts on this subject based on the ideXlab platform.

  • application of elimination voltammetry to adsorptive stripping of dna
    Electroanalysis, 2000
    Co-Authors: Libuse Trnkova, Rene Kizek, Oldřich Dracka
    Abstract:

    Adsorptive stripping voltammetry has been extended by elimination voltammetry with linear scan rate (EVLS). EVLS offers the elimination of selected currents from the linear scan voltammetry results. It can be achieved by an elimination function formed by a linear combination of total currents measured at different scan rates, because the basic idea of elimination of chosen currents (for example the charging current, I-c, the reversible current for Substances transported only by linear diffusion, I-r, and the purely kinetic current, I-k) consists of the different dependence of voltammetric current on the scan rare. In this article, the problem of Substance adsorption influence on the elimination voltammetry results has been studied. Theoretical curves of an irreversible current with Adsorbed Substance being electroactive were calculated for three elimination functions. A: the function eliminating I-k and I-c and conserving I-r B: the function eliminating I-c and I-r. conserving I-k; and C: the function eliminating I-r and I-k and conserving I-c, where I-c, I-r, and I-k are the charging current, the reversible diffusion current, and the kinetic current, respectively. A larger difference between diffusion and adsorption was exhibited by the elimination function A. It provides a substantial increase in resolution and sensitivity as compared to the linear scan voltammetry current peak and clearly marks the adsorption. In case of the adsorption of electroactive Substances this elimination function A can be useful for analytical applications, particularly for the adsorptive stripping voltammetry with electrochemical irreversible systems. As a practical application, the adsorptive stripping voltammetry of thermally denatured DNA on a hanging mercury electrode has been developed. While the LSV signal of single-stranded DNA at low concentrations gives a slight hint of the cathodic peak (due to the reduction of adenine and cytosine residues), the elimination A provides quite a clear signal in the form of the peak-counterpeak. It is possible to determinate DNA at concentrations below micrograms per milliliter by using this elimination function. The results received by the adsorptive stripping voltammetry in the mode of linear scan (LSV), square-wave (SWV) and elimination with linear scan (EVLS) are discussed.

  • application of elimination voltammetry to the electroanalysisof an Adsorbed Substance
    2000
    Co-Authors: Libuse Trnkova, Rene Kizek, Oldřich Dracka
    Abstract:

    In the elimination voltammetry with a linear scan rate (EVLS), elimination of the selected particular currents from the linear scan voltammetry results is achieved by an elimination function formed by a linear combination of the total currents measured at different scan rates.Theoretical curves of an irreversible current with Adsorbed Substance being electroactive were calculated for three elimination functions: A - the function eliminating Ik and Ic and conserving Ir , B - the function eliminating Ic and Ir , conserving Ik , and C - the function eliminating Ir and Ik and conserving Ic, where Ic , Ir , and Ik are the charging current, the reversible diffusion current, and the kinetic current, respectively. A larger difference between diffusion and adsorption was exhibited by the elimination function A. It provides a substantial increase in resolution and sensitivity as compared to the linear scan voltammetry current peak and clearly marks the adsorption.

Rene Kizek - One of the best experts on this subject based on the ideXlab platform.

  • application of elimination voltammetry to adsorptive stripping of dna
    Electroanalysis, 2000
    Co-Authors: Libuse Trnkova, Rene Kizek, Oldřich Dracka
    Abstract:

    Adsorptive stripping voltammetry has been extended by elimination voltammetry with linear scan rate (EVLS). EVLS offers the elimination of selected currents from the linear scan voltammetry results. It can be achieved by an elimination function formed by a linear combination of total currents measured at different scan rates, because the basic idea of elimination of chosen currents (for example the charging current, I-c, the reversible current for Substances transported only by linear diffusion, I-r, and the purely kinetic current, I-k) consists of the different dependence of voltammetric current on the scan rare. In this article, the problem of Substance adsorption influence on the elimination voltammetry results has been studied. Theoretical curves of an irreversible current with Adsorbed Substance being electroactive were calculated for three elimination functions. A: the function eliminating I-k and I-c and conserving I-r B: the function eliminating I-c and I-r. conserving I-k; and C: the function eliminating I-r and I-k and conserving I-c, where I-c, I-r, and I-k are the charging current, the reversible diffusion current, and the kinetic current, respectively. A larger difference between diffusion and adsorption was exhibited by the elimination function A. It provides a substantial increase in resolution and sensitivity as compared to the linear scan voltammetry current peak and clearly marks the adsorption. In case of the adsorption of electroactive Substances this elimination function A can be useful for analytical applications, particularly for the adsorptive stripping voltammetry with electrochemical irreversible systems. As a practical application, the adsorptive stripping voltammetry of thermally denatured DNA on a hanging mercury electrode has been developed. While the LSV signal of single-stranded DNA at low concentrations gives a slight hint of the cathodic peak (due to the reduction of adenine and cytosine residues), the elimination A provides quite a clear signal in the form of the peak-counterpeak. It is possible to determinate DNA at concentrations below micrograms per milliliter by using this elimination function. The results received by the adsorptive stripping voltammetry in the mode of linear scan (LSV), square-wave (SWV) and elimination with linear scan (EVLS) are discussed.

  • application of elimination voltammetry to the electroanalysisof an Adsorbed Substance
    2000
    Co-Authors: Libuse Trnkova, Rene Kizek, Oldřich Dracka
    Abstract:

    In the elimination voltammetry with a linear scan rate (EVLS), elimination of the selected particular currents from the linear scan voltammetry results is achieved by an elimination function formed by a linear combination of the total currents measured at different scan rates.Theoretical curves of an irreversible current with Adsorbed Substance being electroactive were calculated for three elimination functions: A - the function eliminating Ik and Ic and conserving Ir , B - the function eliminating Ic and Ir , conserving Ik , and C - the function eliminating Ir and Ik and conserving Ic, where Ic , Ir , and Ik are the charging current, the reversible diffusion current, and the kinetic current, respectively. A larger difference between diffusion and adsorption was exhibited by the elimination function A. It provides a substantial increase in resolution and sensitivity as compared to the linear scan voltammetry current peak and clearly marks the adsorption.

Bernhard M Krooss - One of the best experts on this subject based on the ideXlab platform.

  • high pressure sorption isotherms and sorption kinetics of ch4 and co2 on coals
    Fuel, 2010
    Co-Authors: Qinfu Liu, Philipp Weniger, Yves Gensterblum, Andreas Busch, Bernhard M Krooss
    Abstract:

    Abstract Using a manometric experimental setup, high-pressure sorption measurements with CH 4 and CO 2 were performed on three Chinese coal samples of different rank (VR r  = 0.53%, 1.20%, and 3.86%). The experiments were conducted at 35, 45, and 55 °C with pressures up to 25 MPa on the 0.354–1 mm particle fraction in the dry state. The objective of this study was to explore the accuracy and reproducibility of the manometric method in the pressure and temperature range relevant for potential coalbed methane (CBM) and CO 2 -enhanced CBM (CO 2 -ECBM) activities ( P  > 8 MPa, T  > 35 °C). Maximum experimental errors were estimated using the Gauss error propagation theorem, and reproducibility tests of the high-pressure sorption measurements for CH 4 and CO 2 were performed. Further, the experimental data presented here was used to explicitly study the CO 2 sorption behaviour of Chinese coal samples in the elevated pressure range (up to 25 MPa) and the effects of temperature on supercritical CO 2 sorption isotherms. The experiments provided characteristic excess sorption isotherms which, in the case of CO 2 exhibit a maximum around the critical pressure and then decline and level out towards a constant value. The results of these manometric tests are consistent with those of previous gravimetric sorption studies and corroborate a crossover of the 35, 45, and 55 °C CO 2 excess sorption isotherms in the high-pressure range. The measurement range could be extended, however, to significantly higher pressures. The excess sorption isotherms tend to converge, indicating that the temperature dependence of CO 2 excess sorption on coals at high-pressures (>20 MPa) becomes marginal. Further, all CO 2 high-pressure isotherms measured in this study were approximated by a three-parameter excess sorption function with special consideration of the density ratio of the “free” phase and the sorbed phase. This function provided a good representation of the experimental data. The maximum excess sorption capacity of the three coal samples for methane ranged from 0.8 to 1.6 mmol/g (dry, ash-free) and increased from medium volatile bituminous to subbituminous to anthracite. The medium volatile bituminous coal also exhibited the lowest overall excess sorption capacity for CO 2 . However, the subbituminous coal was found to have the highest CO 2 sorption capacity of the three samples. The mass fraction of Adsorbed Substance as a function of time recorded during the first pressure step was used to analyze the kinetics of CH 4 and CO 2 sorption on the coal samples. CO 2 sorption proceeds more rapidly than CH 4 sorption on the anthracite and the medium volatile bituminous coal. For the subbituminous coal, methane sorption is initially faster, but during the final stage of the measurement CO 2 sorption approaches the equilibrium value more rapidly than methane.

Qinfu Liu - One of the best experts on this subject based on the ideXlab platform.

  • high pressure sorption isotherms and sorption kinetics of ch4 and co2 on coals
    Fuel, 2010
    Co-Authors: Qinfu Liu, Philipp Weniger, Yves Gensterblum, Andreas Busch, Bernhard M Krooss
    Abstract:

    Abstract Using a manometric experimental setup, high-pressure sorption measurements with CH 4 and CO 2 were performed on three Chinese coal samples of different rank (VR r  = 0.53%, 1.20%, and 3.86%). The experiments were conducted at 35, 45, and 55 °C with pressures up to 25 MPa on the 0.354–1 mm particle fraction in the dry state. The objective of this study was to explore the accuracy and reproducibility of the manometric method in the pressure and temperature range relevant for potential coalbed methane (CBM) and CO 2 -enhanced CBM (CO 2 -ECBM) activities ( P  > 8 MPa, T  > 35 °C). Maximum experimental errors were estimated using the Gauss error propagation theorem, and reproducibility tests of the high-pressure sorption measurements for CH 4 and CO 2 were performed. Further, the experimental data presented here was used to explicitly study the CO 2 sorption behaviour of Chinese coal samples in the elevated pressure range (up to 25 MPa) and the effects of temperature on supercritical CO 2 sorption isotherms. The experiments provided characteristic excess sorption isotherms which, in the case of CO 2 exhibit a maximum around the critical pressure and then decline and level out towards a constant value. The results of these manometric tests are consistent with those of previous gravimetric sorption studies and corroborate a crossover of the 35, 45, and 55 °C CO 2 excess sorption isotherms in the high-pressure range. The measurement range could be extended, however, to significantly higher pressures. The excess sorption isotherms tend to converge, indicating that the temperature dependence of CO 2 excess sorption on coals at high-pressures (>20 MPa) becomes marginal. Further, all CO 2 high-pressure isotherms measured in this study were approximated by a three-parameter excess sorption function with special consideration of the density ratio of the “free” phase and the sorbed phase. This function provided a good representation of the experimental data. The maximum excess sorption capacity of the three coal samples for methane ranged from 0.8 to 1.6 mmol/g (dry, ash-free) and increased from medium volatile bituminous to subbituminous to anthracite. The medium volatile bituminous coal also exhibited the lowest overall excess sorption capacity for CO 2 . However, the subbituminous coal was found to have the highest CO 2 sorption capacity of the three samples. The mass fraction of Adsorbed Substance as a function of time recorded during the first pressure step was used to analyze the kinetics of CH 4 and CO 2 sorption on the coal samples. CO 2 sorption proceeds more rapidly than CH 4 sorption on the anthracite and the medium volatile bituminous coal. For the subbituminous coal, methane sorption is initially faster, but during the final stage of the measurement CO 2 sorption approaches the equilibrium value more rapidly than methane.