Simultaneous Detection of Homocysteine and Cysteine in the Presence of Ascorbic Acid and Glutathione Using a Nanocarbon Modified Electrode

The simultaneous electrochemical detection of homocysteine and cysteine using an absorbed ortho-quinone species, catechol, at the nanocarbon modified glassy carbon electrode was achieved via 1,4-Michael addition reaction. The detection was done in the presence and the absence of each other as well as with both glutathione and ascorbic acid present in order to investigate the selectivity of homocysteine and cysteine. A determination of homocysteine sensitivity is (0.882±0.296)nAnM-1 with a LOD of ca. 11nM and cysteine sensitivity is (7.501±0.202)mAμM-1 with a LOD of ca. 5.0μM within a range of 0-0.1mM. © 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim

The selective electrochemical detection of homocysteine in the presence of glutathione, cysteine, and ascorbic acid using carbon electrodes.

The detection of homocysteine, HCys, was achieved with the use of catechol via 1,4-Michael addition reaction using carbon electrodes: a glassy carbon electrode and a carbon nanotube modified glassy carbon electrode. The selective detection of homocysteine was investigated and achieved in the absence and presence of glutathione, cysteine and ascorbic acid using cyclic voltammetry and square wave voltammetry. A calibration curve of homocysteine detection was determined and the sensitivity is (0.20 ± 0.02) μA μM(-1) and the limit of detection is 660 nM within the linear range. Lastly, commercially available multi walled carbon nanotube screen printed electrodes were applied to the system for selective homocysteine detection. This work presents a potential practical application towards medical applications as it can be highly beneficial towards quality healthcare management

Towards Detection of Total Antioxidant Concentrations of Glutathione, Cysteine, Homocysteine and Ascorbic Acid Using a Nanocarbon Paste Electrode

The electrocatalytic reaction between catechol and the antioxidants, glutathione, cysteine, homocysteine and ascorbic acid is studied at a nanocarbon paste electrode and used to measure the total antioxidant concentration in aqueous solution. Two different approaches are described: one in which catechol is dissolved in solution and the second in which catechol is dissolved into the nanocarbon paste electrode. Similar limits of detection of 2.0μM and 1.9μM and sensitivities of 8.8×10-3μA/μM and 0.11μM-1 are reported, respectively at nanocarbon and nanocarbon-catechol paste electrodes. Three different commercial multivitamin drug samples were analysed and the results were in a good agreement with those from independent analysis. © 2014 The Authors

Towards Detection of Total Antioxidant Concentrations of Glutathione, Cysteine, Homocysteine and Ascorbic Acid Using a Nanocarbon Paste Electrode

The electrocatalytic reaction between catechol and the antioxidants, glutathione, cysteine, homocysteine and ascorbic acid is studied at a nanocarbon paste electrode and used to measure the total antioxidant concentration in aqueous solution. Two different approaches are described: one in which catechol is dissolved in solution and the second in which catechol is dissolved into the nanocarbon paste electrode. Similar limits of detection of 2.0μM and 1.9μM and sensitivities of 8.8×10-3μA/μM and 0.11μM-1 are reported, respectively at nanocarbon and nanocarbon-catechol paste electrodes. Three different commercial multivitamin drug samples were analysed and the results were in a good agreement with those from independent analysis. © 2014 The Authors

The selective electrochemical detection of homocysteine in the presence of glutathione, cysteine, and ascorbic acid using carbon electrodes.

The detection of homocysteine, HCys, was achieved with the use of catechol via 1,4-Michael addition reaction using carbon electrodes: a glassy carbon electrode and a carbon nanotube modified glassy carbon electrode. The selective detection of homocysteine was investigated and achieved in the absence and presence of glutathione, cysteine and ascorbic acid using cyclic voltammetry and square wave voltammetry. A calibration curve of homocysteine detection was determined and the sensitivity is (0.20 ± 0.02) μA μM(-1) and the limit of detection is 660 nM within the linear range. Lastly, commercially available multi walled carbon nanotube screen printed electrodes were applied to the system for selective homocysteine detection. This work presents a potential practical application towards medical applications as it can be highly beneficial towards quality healthcare management

Electrocatalytic Detection of Glutathione - the Search for New Mediators

We report the possibility to use different mediators such as acetaminophen, 4-aminophenol, 4-amino-2,6-dichlorophenol and 4-amino-2,6-diphenylphenol to detect glutathione using a nanocarbon paste electrode. The detection is based on the electrocatalytic response involving the electrochemically generated quinoneimines and glutathione. 4-aminophenol is recommended as the most sensitive mediator in terms of giving the lowest limit detection of 0.80 μmol L-1

The Measurement of the Gibbs Energy of Transfer Between Oil and Water Using a Nano-Carbon Paste Electrode

The use of nano-carbon paste electrodes for the measurement of Gibbs energies of transfer between oil and aqueous phases is reported. In this method the oil of interest is used as the binder for the nano-carbon paste electrodes and the molecule of interest is dissolved in the organic or aqueous phase. Voltammetry is performed over a period of time and used to monitor the transfer of the molecule between the two phases. The method is illustrated for the transfer of ferrocenemethanol between water and oil using the ferrocenemethanol / ferroceniummethanol (FcCH2OH/FcCH2OH+) redox couple. Three pairs of voltammetric peaks were observed in a 0.1M KCl solution when the nano-carbon paste electrode was modified by dissolution of FcCH2OH in the binder oil: P1 [E=0.23V, 0.17V vs. Ag/AgCl (1M KCl)], P2 [E=0.36V, 0.32V vs. Ag/AgCl (1M KCl)] and P3 [E=0.55V, 0.46V vs. Ag/AgCl (1M KCl)]. These are assigned to the FcCH2OH species existing in the aqueous solution [FcCH2OH(aq)/FcCH2OH+(aq)], originating in the oil (o) [FcCH2OH(o)/FcCH2OH+(aq)] and to oxidation of adsorbed (ads) material on the nano-carbon [FcCH2OH(ads)] respectively. When supporting electrolyte containing the anions Cl-, NO3- or SCN- was used, an expulsion of the oxidised ferrocene occurred and the difference in midpoint potentials (Emid) between the peaks P1 and P2 observed in these experiments allowed the calculation of the Gibbs energy (ΔG°) of transfer of ferrocenemethanol from water to oil. The average ΔG° value thus obtained was (-12.7±0.2) kJmol-1. For more hydrophobic anions (X-=PF6-, AsF6-), the electron transfer is coupled to the transfer of the anion into the oil and the ΔG° for the transfer of the ion pair of FcCH2OH+ and X- ions from water to oil was found to be -1.3 and -3.9kJmol-1 for PF6- and AsF6- respectively. © 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim

The Measurement of the Gibbs Energy of Transfer Between Oil and Water Using a Nano-Carbon Paste Electrode

The use of nano-carbon paste electrodes for the measurement of Gibbs energies of transfer between oil and aqueous phases is reported. In this method the oil of interest is used as the binder for the nano-carbon paste electrodes and the molecule of interest is dissolved in the organic or aqueous phase. Voltammetry is performed over a period of time and used to monitor the transfer of the molecule between the two phases. The method is illustrated for the transfer of ferrocenemethanol between water and oil using the ferrocenemethanol / ferroceniummethanol (FcCH2OH/FcCH2OH+) redox couple. Three pairs of voltammetric peaks were observed in a 0.1M KCl solution when the nano-carbon paste electrode was modified by dissolution of FcCH2OH in the binder oil: P1 [E=0.23V, 0.17V vs. Ag/AgCl (1M KCl)], P2 [E=0.36V, 0.32V vs. Ag/AgCl (1M KCl)] and P3 [E=0.55V, 0.46V vs. Ag/AgCl (1M KCl)]. These are assigned to the FcCH2OH species existing in the aqueous solution [FcCH2OH(aq)/FcCH2OH+(aq)], originating in the oil (o) [FcCH2OH(o)/FcCH2OH+(aq)] and to oxidation of adsorbed (ads) material on the nano-carbon [FcCH2OH(ads)] respectively. When supporting electrolyte containing the anions Cl-, NO3- or SCN- was used, an expulsion of the oxidised ferrocene occurred and the difference in midpoint potentials (Emid) between the peaks P1 and P2 observed in these experiments allowed the calculation of the Gibbs energy (ΔG°) of transfer of ferrocenemethanol from water to oil. The average ΔG° value thus obtained was (-12.7±0.2) kJmol-1. For more hydrophobic anions (X-=PF6-, AsF6-), the electron transfer is coupled to the transfer of the anion into the oil and the ΔG° for the transfer of the ion pair of FcCH2OH+ and X- ions from water to oil was found to be -1.3 and -3.9kJmol-1 for PF6- and AsF6- respectively. © 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim