title: Development of amperometric biosensors for the determination of glycolic acid in real samples.
abstract: The first enzyme-based biosensors capable of determining glycolic acid in various complex matrixes, such as cosmetics, instant coffee, and urine, are presented in this paper. Two separate designs, both based on a three-membrane configuration consisting of an inner cellulose acetate membrane (CA) and an outer polycarbonate membrane (PC), which sandwich a membrane bearing the biomolecule(s), are proposed. Glycolate oxidase was immobilized onto a modified polyethersulfonate membrane by means of chemical bonding, and glycolate oxidase/catalase enzyme mixture was immobilized into a mixed-ester cellulose acetate membrane through physical adsorption. The membrane assemblies were mounted on an amperometric flow cell (hydrogen peroxide detection at a platinum anode poised at +0.65 V vs Ag/AgCl/3 KCl) or on an oxygen electrode, respectively. Both configurations were optimized with respect to various working parameters. The proposed biosensors are interference-free to common electroactive species and were successfully applied for the determination of glycolic acid in various samples, showing an excellent agreement with a reference photometric method. The validity of the proposed method in samples, in which the reference method was not applicable, was tested with recovery studies. Values of 102 +/- % were obtained. Inherent interference of oxalic acid was manipulated by using a primary amine-containing buffer and the enzyme catalase. Both systems were designed in order to be compatible with the current technology of the most widely used commercial analyzers.
authors.affiliation: Department of Chemistry, University of Ioannina, Greece.
authors.forename: Constantinos G
authors.initials: CG
authors.lastname: Tsiafoulis
authors.forename: Mamas I
authors.initials: MI
authors.lastname: Prodromidis
authors.forename: Miltiades I
authors.initials: MI
authors.lastname: Karayannis
mesh_terms: D000429:Alcohol Oxidoreductases; D015374:Biosensing Techniques / Q000379:methods*; D003069:Coffee / Q000737:chemistry; D003358:Cosmetics / Q000032:analysis; D004800:Enzymes, Immobilized; D006016:Glycolates / Q000032:analysis*; D006801:Humans; D008839:Microelectrodes; D014556:Urine / Q000737:chemistry
chemical_list: D003069:Coffee; D003358:Cosmetics; D004800:Enzymes, Immobilized; D006016:Glycolates; D000429:Alcohol Oxidoreductases; C020821:glycollate oxidase