Enzyme Electrodes for the Determination of 1-Phenylalanine

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Abstract
Two different kinds of enzyme electrodes suitable for the determination of 1-phenylalanine are described. The 1-phenylalanine electrode built based on an ion-selective iodide electrode uses a dual enzyme reaction layer – 1-amino acid oxidase (1-AAO), horseradish peroxidase (HRP) – chemically immobilized in polyacryl gel. The electrode function is based on the reaction: The constant I- concentration of the sample solution decreases locally at the electrode surface in the presence of 1-phenylalanine (1-PA). The 1-phenylalanine electrode built on a silicone rubber based antibiotic type ammonium selective electrode was fabricated with a chemically immobilized 1-amino acid oxidase, as reaction layer. The 1-phenylalanine diffuses into the enzyme layer where it is converted to m4t ions which are sensed by the antibiotic membrane which is selective for NH4 + ions. A potential is produced which is a log function of the concentration of 1 -phenylalanine.