title: Chiral analysis of amino acids using electrochemical composite bienzyme biosensors.
abstract: The construction and performance of bienzyme amperometric composite biosensors for the selective determination of l- or d-amino acids is reported. D- or L-Amino acid oxidase, horseradish peroxidase, and the mediator ferrocene were coimmobilized by simple physical inclusion into the bulk of a graphite-70% Teflon electrode matrix. Working conditions including amino acid oxidase loading and pH were optimized. Studies on the repeatability of the amperometric response obtained at +0.00 V, with and without regeneration of the electrode surface by polishing, on the useful lifetime of one single biosensor and on the reproducibility in the fabrication of different biosensors illustrate the robustness of the bioelectrodes design. Calibration plots by both amperometry in stirred solutions and flow injection with amperometric detection were obtained for L-arginine, L-phenylalanine, L-leucine, L-methionine, L-tryptophan, D-leucine, D-methionine, D-serine, and D-valine. Differences in sensitivity were discussed in terms of the hydrophobicity of the substrate and of the electrode surface. The bienzyme composite electrode was applied to the determination of L- and D-amino acids in racemic samples, as well as to the estimation of the L-amino acids content in muscatel grapes.
authors.affiliation: Department of Analytical Chemistry, Complutense University of Madrid, Madrid, 28040, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Domínguez
authors.forename: B
authors.initials: B
authors.lastname: Serra
authors.forename: A J
authors.initials: AJ
authors.lastname: Reviejo
authors.forename: J M
authors.initials: JM
authors.lastname: Pingarrón
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000737:chemistry; D000596:Amino Acids / Q000032:analysis*; D015374:Biosensing Techniques / Q000379:methods*; D003605:D-Amino-Acid Oxidase / Q000737:chemistry; D004563:Electrochemistry / Q000379:methods*; D005296:Ferrous Compounds / Q000737:chemistry; D006108:Graphite / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000737:chemistry; D050830:L-Amino Acid Oxidase; D000075163:Metallocenes; D011138:Polytetrafluoroethylene / Q000737:chemistry; D027843:Vitis / Q000378:metabolism
chemical_list: D000596:Amino Acids; D005296:Ferrous Compounds; D000075163:Metallocenes; D006108:Graphite; D011138:Polytetrafluoroethylene; D006735:Horseradish Peroxidase; D000594:Amino Acid Oxidoreductases; D050830:L-Amino Acid Oxidase; D003605:D-Amino-Acid Oxidase; C004998:ferrocene