A MEDIATED AMPEROMETRIC ENZYME ELECTRODE USING TETRATHIAFULVALENE AND L-GLUTAMATE OXIDASE FOR THE DETERMINATION OF L-GLUTAMIC ACID

A mediated amperometric sensor for measuring L-glutamate is described. The sensor is based on a carbon paste electrode containing the electron transfer mediator tetrathiafulvalene (TTF), and the enzyme L-glutamate oxidase immobilized on the electrode surface. The enzyme is crosslinked with glutaraldehyde and the matrix held on the electrode surface using an electrochemically deposited polymer. TTF is shown to efficiently reoxidize the reduced flavin adenine dinucleotide centers of glutamate oxidase, permitting operation of the sensor at low applied potentials. The electrode, when operated at +0.15 V (vs. Ag/AgCl), responded linearly to L-glutamate concentrations up to 0.8 mM, the lower detection limit being 2.6 muM, with a response time of 2 min. The sensor was used for the determination of L-glutamate in food samples, with excellent correlations achieved when compared to results obtained by enzymatic analysis using glutamate dehydrogenase. The enzyme electrode exhibits excellent reproducibility and stability, retaining more than 90% of its original activity over a period of 3 weeks.