The Experts below are selected from a list of 8223 Experts worldwide ranked by ideXlab platform
Richard G Compton - One of the best experts on this subject based on the ideXlab platform.
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oxygenated edge plane sites slow the electron transfer of the ferro Ferricyanide redox couple at graphite electrodes
ChemPhysChem, 2006Co-Authors: Craig E Banks, Alison Crossley, Richard G ComptonAbstract:The electron transfer kinetics of ferrocyanide, potassium hexachloroiridate(III), hexaammineruthenium(III) chloride, and N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) have been examined at basal plane and edge plane pyrolytic graphite electrodes which have been allowed to oxidise in air for various periods of time. It is demonstrated via voltammetric and X-ray photoelectron spectroscopy (XPS) analysis that oxygenated species formed at edge plane sites/defects decrease the electron transfer kinetics of ferrocyanide but that the rates for potassium hexachloroiridate(III), hexaammineruthenium(III) chloride and TMPD are insensitive to the oxygenated species. The behaviour of the ferro-/Ferricyanide couple contrasts with that seen on single-walled carbon nanotubes where oxygenation of the tube ends is known to speed up the electron transfer kinetics (A. Chou, T. Bocking, N. K. Singh, J. J. Gooding, Chem. Commun. 2005, 842); the possible reasons for this contrasting behaviour are discussed.
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the oxidation of cysteine by aqueous Ferricyanide a kinetic study using boron doped diamond electrode voltammetry
Electroanalysis, 2002Co-Authors: Olga Nekrassova, Nathan S Lawrence, Li Jiang, Timothy G J Jones, Gary D Allen, Richard G ComptonAbstract:The oxidation of cysteine by Ferricyanide is well established. However, electrochemical studies of the mechanism have to date been underdeveloped due to the lack of resolution between the oxidation waves of the ferrocyanide and cysteine on most electrode materials. It is shown that on boron doped diamond electrode, unlike for example platinum electrodes, the voltammetric responses of the ferrocyanide wave and the targets are sufficiently different, with the former at a lower oxidizing potential, to permit examination of the kinetics of the homogeneous oxidation via voltammetric methods. Accordingly conventional cyclic voltammetry using a BDD electrode is used to show that an EC′ mechanism occurs and rate constants deduced. Both the protonated and de-protonated forms of cysteine (pKa=10.5) are shown to undergo oxidation by Ferricyanide. The cyclic voltammetry data obtained is corroborated by use of channel flow cell experiments with excellent agreement shown between the two techniques for deduced values of the homogeneous electrocatalytic rate constants: Channel electrodes are seen to provide a convenient means to allow quantitative mechanistic hydrodynamic voltammetry at BDD electrodes.
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amperometric detection of sulfide at a boron doped diamond electrode the electrocatalytic reaction of sulfide with Ferricyanide in aqueous solution
Electroanalysis, 2002Co-Authors: Nathan S Lawrence, Mary Thompson, Cesar Prado, Li Jiang, Timothy G J Jones, Richard G ComptonAbstract:The oxidation of sulfide at a boron doped diamond (BDD) electrode has been examined and its analytical utility appraised and compared with other common electrode substrates (Pt, Au, glassy carbon). The suitability of using BDD as a sulfide sensing substrate has been assessed through examining the electrocatalytic oxidation of ferrocyanide to Ferricyanide in the presence of sulfide using both cyclic voltammetry and chronoamperometry. The high oxidation potential for the direct oxidation of sulfide at a BDD electrode allows clear resolution of both the ferrocyanide wave and sulfide oxidation wave producing a distinct analytical signal at the oxidation peak potential of ferrocyanide. The procedure was applied to the recovery of a sulfide spike in sewage effluents with a recovery of 102±4.5%.
Richard John - One of the best experts on this subject based on the ideXlab platform.
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evaluating use of Ferricyanide mediated respiration bioassays to quantify stimulatory and inhibitory effects on escherichia coli populations
Talanta, 2010Co-Authors: Kylie Patricia Catterall, David Robertson, Peter R Teasdale, David T Welsh, Richard JohnAbstract:A number of recent studies have utilised Ferricyanide as a respiratory mediator for microbial-based assays for determining water quality parameters such as biochemical oxygen demand (BOD) and toxicity. The majority of assays published to date obtain a result by determining the difference in ferrocyanide accumulation between a test sample and one or more control samples. However, a validation of the relationship between ferrocyanide accumulation and standard measures of cell density or viability has not yet been performed. To this end, a rapid microbially catalysed Ferricyanide-mediated respiration (FM-RES) assay was compared with standard plate count (SPC) and spectrophotometer (OD(600)) measurements on a growing batch culture of Escherichia coli. Good agreement was observed between all techniques, with predictable deviations noted in different phases of the growth curves. Standardised FM-RES assays showed excellent correlations with the SPC method under controlled conditions, indicating that short-term changes in microbial activity are due to a change in per-cell respiration, rather than changes in cell numbers. The FM-RES assay was then used to observe the changes in the respiration of E. coli induced by the addition of a glucose-glutamic acid (GGA) mixture, 3,5-dichlorophenol (3,5-DCP) and Ag(+) in various combinations and concentrations. Stimulation of respiration was pronounced in the presence of GGA while both 3,5-DCP and, in particular, Ag(+) demonstrated inhibitory respiratory effects. The results highlight the validity and suitability of Ferricyanide-mediated respiration bioassays, with appropriate modification, to monitor either stimulatory effects on microbial populations, such as occurs with BOD, or inhibitory effects, such as occurs with toxicity assays.
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the use of microorganisms with broad range substrate utilisation for the Ferricyanide mediated rapid determination of biochemical oxygen demand
Talanta, 2001Co-Authors: Kylie Patricia Catterall, Kristy Nicole Morris, Huijun Zhao, Neil Pasco, Calvin John Gladman, Richard JohnAbstract:The feasibility of replacing oxygen with a synthetic electron acceptor in microbial catabolism was investigated as a rapid method for the determination of biochemical oxygen demand (BOD). Microorganisms known for their broad range organic substrate utilisation were investigated. It was shown that Trichosporon cutaneum, Pseudomonas putida and Bacillus licheniformis could utilize the Ferricyanide ion as an alternative electron acceptor, in place of oxygen, for the catabolic oxidation of a range of simple organic compounds. The biochemical reactions were monitored by measuring the amount of microbially produced ferrocyanide using amperometry at a Pt disk microelectrode. Catabolic degradation efficiencies approaching those of the conventional 5-day assay were achieved in 1 h. BOD5 equivalent values for a range of simple organic solutions were determined for each of the microorganisms. The effect of increased incubation time and the choice of appropriate calibration standards for rapid BOD assays were also considered.
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Ferricyanide mediated biochemical oxygen demand - development of a rapid biochemical oxygen demand assay
Analytica Chimica Acta, 2001Co-Authors: Kristy Nicole Morris, Kylie Patricia Catterall, Huijun Zhao, Neil Pasco, Richard JohnAbstract:Abstract The use of an artificial electron acceptor in microbial respiration was investigated with a view to developing a rapid assay for biochemical oxygen demand (BOD). The use of Ferricyanide resulted in a significant increase in the rate of the biochemical reaction and allowed for biodegradative conversion efficiencies similar to the 5-day BOD assay to be achieved in 1 h. The extent and rate of the Ferricyanide mediated microbial reaction was determined by monitoring the concentration of the microbially produced ferrocyanide during or after incubation of microorganisms in the presence of Ferricyanide and organic substrate. Spectrophotometry, potentiometry and amperometry using microelectrodes were evaluated as detection methods, with the latter providing the most convenient, stable and reproducible results. Experimental parameters investigated included incubation time, incubation temperature, microbial concentration, Ferricyanide concentration and substrate concentration. In all cases, the results obtained were analogous to that expected in conventional aerobic microbial oxidation of organic material, with the major difference being the considerable increase in rate. The microorganisms used in this study were Escherichia coli and Pseudomonas putida . Results showed that while E. coli could successfully catabolise a standard BOD solution containing glucose and glutamic acid, its use for other substrates was limited. Preliminary investigations into the use of P. putida , however, showed significantly improved performance and demonstrated the promise of this approach for rapid BOD determinations.
Kylie Patricia Catterall - One of the best experts on this subject based on the ideXlab platform.
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evaluating use of Ferricyanide mediated respiration bioassays to quantify stimulatory and inhibitory effects on escherichia coli populations
Talanta, 2010Co-Authors: Kylie Patricia Catterall, David Robertson, Peter R Teasdale, David T Welsh, Richard JohnAbstract:A number of recent studies have utilised Ferricyanide as a respiratory mediator for microbial-based assays for determining water quality parameters such as biochemical oxygen demand (BOD) and toxicity. The majority of assays published to date obtain a result by determining the difference in ferrocyanide accumulation between a test sample and one or more control samples. However, a validation of the relationship between ferrocyanide accumulation and standard measures of cell density or viability has not yet been performed. To this end, a rapid microbially catalysed Ferricyanide-mediated respiration (FM-RES) assay was compared with standard plate count (SPC) and spectrophotometer (OD(600)) measurements on a growing batch culture of Escherichia coli. Good agreement was observed between all techniques, with predictable deviations noted in different phases of the growth curves. Standardised FM-RES assays showed excellent correlations with the SPC method under controlled conditions, indicating that short-term changes in microbial activity are due to a change in per-cell respiration, rather than changes in cell numbers. The FM-RES assay was then used to observe the changes in the respiration of E. coli induced by the addition of a glucose-glutamic acid (GGA) mixture, 3,5-dichlorophenol (3,5-DCP) and Ag(+) in various combinations and concentrations. Stimulation of respiration was pronounced in the presence of GGA while both 3,5-DCP and, in particular, Ag(+) demonstrated inhibitory respiratory effects. The results highlight the validity and suitability of Ferricyanide-mediated respiration bioassays, with appropriate modification, to monitor either stimulatory effects on microbial populations, such as occurs with BOD, or inhibitory effects, such as occurs with toxicity assays.
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the use of microorganisms with broad range substrate utilisation for the Ferricyanide mediated rapid determination of biochemical oxygen demand
Talanta, 2001Co-Authors: Kylie Patricia Catterall, Kristy Nicole Morris, Huijun Zhao, Neil Pasco, Calvin John Gladman, Richard JohnAbstract:The feasibility of replacing oxygen with a synthetic electron acceptor in microbial catabolism was investigated as a rapid method for the determination of biochemical oxygen demand (BOD). Microorganisms known for their broad range organic substrate utilisation were investigated. It was shown that Trichosporon cutaneum, Pseudomonas putida and Bacillus licheniformis could utilize the Ferricyanide ion as an alternative electron acceptor, in place of oxygen, for the catabolic oxidation of a range of simple organic compounds. The biochemical reactions were monitored by measuring the amount of microbially produced ferrocyanide using amperometry at a Pt disk microelectrode. Catabolic degradation efficiencies approaching those of the conventional 5-day assay were achieved in 1 h. BOD5 equivalent values for a range of simple organic solutions were determined for each of the microorganisms. The effect of increased incubation time and the choice of appropriate calibration standards for rapid BOD assays were also considered.
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Ferricyanide mediated biochemical oxygen demand - development of a rapid biochemical oxygen demand assay
Analytica Chimica Acta, 2001Co-Authors: Kristy Nicole Morris, Kylie Patricia Catterall, Huijun Zhao, Neil Pasco, Richard JohnAbstract:Abstract The use of an artificial electron acceptor in microbial respiration was investigated with a view to developing a rapid assay for biochemical oxygen demand (BOD). The use of Ferricyanide resulted in a significant increase in the rate of the biochemical reaction and allowed for biodegradative conversion efficiencies similar to the 5-day BOD assay to be achieved in 1 h. The extent and rate of the Ferricyanide mediated microbial reaction was determined by monitoring the concentration of the microbially produced ferrocyanide during or after incubation of microorganisms in the presence of Ferricyanide and organic substrate. Spectrophotometry, potentiometry and amperometry using microelectrodes were evaluated as detection methods, with the latter providing the most convenient, stable and reproducible results. Experimental parameters investigated included incubation time, incubation temperature, microbial concentration, Ferricyanide concentration and substrate concentration. In all cases, the results obtained were analogous to that expected in conventional aerobic microbial oxidation of organic material, with the major difference being the considerable increase in rate. The microorganisms used in this study were Escherichia coli and Pseudomonas putida . Results showed that while E. coli could successfully catabolise a standard BOD solution containing glucose and glutamic acid, its use for other substrates was limited. Preliminary investigations into the use of P. putida , however, showed significantly improved performance and demonstrated the promise of this approach for rapid BOD determinations.
Dan Shan - One of the best experts on this subject based on the ideXlab platform.
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ferrocyanide Ferricyanide redox couple induced electrochemiluminescence amplification of carbon dots for ultrasensitive sensing of glutathione
Analytical Chemistry, 2015Co-Authors: Serge Cosnier, Xueji Zhang, Dan ShanAbstract:Here we report a novel solid-state ECL sensor for ultrasensitive sensing of glutathione (GSH) based on ferrocyanide-Ferricyanide redox couple (Fe(CN)63–/4–) induced electrochemiluminescence (ECL) amplification of carbon dots (C-dots). The electropolymerization of C-dots and (11-pyrrolyl-1-yl-undecyl) triethylammonium tetrafluoroborate (A2) enabled immobilization of the hydrophilic C-dots on the surface of glassy carbon electrode (GCE) perfectly, while the excellent conductivity of polypyrrole was exploited to accelerate electron transfer between them. The Fe(CN)63–/4– can expeditiously convert the C-dots and S2O82– to C-dot•– and SO4•–, respectively. High yields of the excited state C-dots (C-dots*) were obtained, and a ∼10-fold ECL amplification was realized. The C-dots* obtained through the recombination of electron-injected and hole-injected processes may be impeded due to the interference of GSH to K2S2O8. Therefore, the constructed sensor for GSH showed a detection limit down to 54.3 nM (S/N = 3) and...
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ferrocyanide Ferricyanide redox couple induced electrochemiluminescence amplification of carbon dots for ultrasensitive sensing of glutathione
Analytical Chemistry, 2015Co-Authors: Wenjun Niu, Serge Cosnier, Xueji Zhang, Ronghui Zhu, Dan ShanAbstract:Here we report a novel solid-state ECL sensor for ultrasensitive sensing of glutathione (GSH) based on ferrocyanide-Ferricyanide redox couple (Fe(CN)6(3-/4-)) induced electrochemiluminescence (ECL) amplification of carbon dots (C-dots). The electropolymerization of C-dots and (11-pyrrolyl-1-yl-undecyl) triethylammonium tetrafluoroborate (A2) enabled immobilization of the hydrophilic C-dots on the surface of glassy carbon electrode (GCE) perfectly, while the excellent conductivity of polypyrrole was exploited to accelerate electron transfer between them. The Fe(CN)6(3-/4-) can expeditiously convert the C-dots and S2O8(2-) to C-dot(•-) and SO4(•-), respectively. High yields of the excited state C-dots (C-dots*) were obtained, and a ∼10-fold ECL amplification was realized. The C-dots* obtained through the recombination of electron-injected and hole-injected processes may be impeded due to the interference of GSH to K2S2O8. Therefore, the constructed sensor for GSH showed a detection limit down to 54.3 nM (S/N = 3) and a wide linear range from 0.1-1.0 μM with a correlation coefficient of 0.997.
Nathan S Lawrence - One of the best experts on this subject based on the ideXlab platform.
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the oxidation of cysteine by aqueous Ferricyanide a kinetic study using boron doped diamond electrode voltammetry
Electroanalysis, 2002Co-Authors: Olga Nekrassova, Nathan S Lawrence, Li Jiang, Timothy G J Jones, Gary D Allen, Richard G ComptonAbstract:The oxidation of cysteine by Ferricyanide is well established. However, electrochemical studies of the mechanism have to date been underdeveloped due to the lack of resolution between the oxidation waves of the ferrocyanide and cysteine on most electrode materials. It is shown that on boron doped diamond electrode, unlike for example platinum electrodes, the voltammetric responses of the ferrocyanide wave and the targets are sufficiently different, with the former at a lower oxidizing potential, to permit examination of the kinetics of the homogeneous oxidation via voltammetric methods. Accordingly conventional cyclic voltammetry using a BDD electrode is used to show that an EC′ mechanism occurs and rate constants deduced. Both the protonated and de-protonated forms of cysteine (pKa=10.5) are shown to undergo oxidation by Ferricyanide. The cyclic voltammetry data obtained is corroborated by use of channel flow cell experiments with excellent agreement shown between the two techniques for deduced values of the homogeneous electrocatalytic rate constants: Channel electrodes are seen to provide a convenient means to allow quantitative mechanistic hydrodynamic voltammetry at BDD electrodes.
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amperometric detection of sulfide at a boron doped diamond electrode the electrocatalytic reaction of sulfide with Ferricyanide in aqueous solution
Electroanalysis, 2002Co-Authors: Nathan S Lawrence, Mary Thompson, Cesar Prado, Li Jiang, Timothy G J Jones, Richard G ComptonAbstract:The oxidation of sulfide at a boron doped diamond (BDD) electrode has been examined and its analytical utility appraised and compared with other common electrode substrates (Pt, Au, glassy carbon). The suitability of using BDD as a sulfide sensing substrate has been assessed through examining the electrocatalytic oxidation of ferrocyanide to Ferricyanide in the presence of sulfide using both cyclic voltammetry and chronoamperometry. The high oxidation potential for the direct oxidation of sulfide at a BDD electrode allows clear resolution of both the ferrocyanide wave and sulfide oxidation wave producing a distinct analytical signal at the oxidation peak potential of ferrocyanide. The procedure was applied to the recovery of a sulfide spike in sewage effluents with a recovery of 102±4.5%.