title: Oxidation and flow-injection amperometric determination of 5-hydroxytryptophan at an electrode modified by electrochemically assisted deposition of a sol-gel film with templated nanoscale pores.
abstract: The oxidation of 5-hydroxytryptophan (5-HTPP) yielded a passivating polymeric film at an indium tin oxide (ITO) electrode. Coating ITO with a nanoscale sol-gel film with a mesoporous structure was shown to change the pathway of the chemical reaction coupled to the electron transfer. The sol-gel film was deposited by an electrochemically assisted process, and the mesoporosity was imparted by including generation-4 poly(amidoamine) dendrimer in the precursor solution. The dendrimer was removed subsequently with an atmospheric oxygen plasma. This electrode remained active during cyclic voltammetry and controlled potential electrolysis of 5-HTPP, which was attributed to dimer, rather than polymer, formation from the oxidation product. Mass spectrometry confirmed this hypothesis. The anodic current was limited by the electron-transfer kinetics. Modification of the sol-gel film by inclusion of cobalt hexacyanoferrate, which catalyzes the oxidation, resulted in a diffusion-limited current. Determination of 5-HTPP by flow-injection amperometry had a detection limit of 17nM.
authors.affiliation: Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA.
authors.forename: David
authors.initials: D
authors.lastname: Ranganathan
authors.forename: Silvia
authors.initials: S
authors.lastname: Zamponi
authors.forename: Mario
authors.initials: M
authors.lastname: Berrettoni
authors.forename: B
authors.initials: B
authors.lastname: Layla Mehdi
authors.forename: James A
authors.initials: JA
authors.lastname: Cox
mesh_terms: D006916:5-Hydroxytryptophan / Q000032:analysis*; D004566:Electrodes; D017022:Flow Injection Analysis; D008855:Microscopy, Electron, Scanning; D036103:Nanotechnology; D010084:Oxidation-Reduction; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D006916:5-Hydroxytryptophan
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