title: The electrochemical oxidation of homocysteine at boron-doped diamond electrodes with application to HPLC amperometric detection.
abstract: The electrochemical oxidation of homocysteine was studied at as-deposited and anodized (oxidized) boron-doped diamond (BDD) thin film electrodes with cyclic voltammetry, flow injection analysis and high-pressure liquid chromatography with amperometric detection. At anodized boron-doped diamond electrodes, highly reproducible, well-defined cyclic voltammograms for homocysteine oxidation were obtained in acidic media, while as-deposited diamond did not provide a detectable signal. In alkaline media, however, the oxidation response was obtained both at as-deposited and anodized diamond electrodes. The potential sweep rate dependence of homocysteine oxidation (peak currents for 1 mM homocysteine linearly proportional to v(1/2), within the range of 0.01 to 0.3 V s(-1)) indicates that the oxidation involves a diffusing species, with negligible adsorption on the BDD surface at this concentration. In the flow system, BDD exhibited a highly reproducible amperometric response, with a peak variation less than 2%. An extremely low detection limit (1 nM) was obtained at 1.6 V vs. Ag/AgCl. In addition, the determination of homocysteine in a standard mixture with aminothiols and disulfide compounds by means of isocratic reverse-phase HPLC with amperometric detection at diamond electrodes has been investigated. The results showed excellent separation, with a detection limit of 1 pmol and a linear range of three orders of magnitude.
authors.affiliation: Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.
authors.forename: O
authors.initials: O
authors.lastname: Chailapakul
authors.forename: W
authors.initials: W
authors.lastname: Siangproh
authors.forename: B V
authors.initials: BV
authors.lastname: Sarada
authors.forename: C
authors.initials: C
authors.lastname: Terashima
authors.forename: Tata N
authors.initials: TN
authors.lastname: Rao
authors.forename: D A
authors.initials: DA
authors.lastname: Tryk
authors.forename: A
authors.initials: A
authors.lastname: Fujishima
mesh_terms: D001895:Boron; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004563:Electrochemistry; D004566:Electrodes; D006710:Homocysteine / Q000032:analysis*; D010084:Oxidation-Reduction
chemical_list: D006710:Homocysteine; D001895:Boron