Enzyme-based chemically amplified flow-injection determination of catechol and catecholamines using an immobilized tyrosinase reactor and l-ascorbic acid
✍ Scribed by Yasushi Hasebe; Kenichiro Takamori; Shunichi Uchiyama
- Publisher
- Elsevier Science
- Year
- 1993
- Tongue
- English
- Weight
- 450 KB
- Volume
- 282
- Category
- Article
- ISSN
- 0003-2670
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✦ Synopsis
Substrate recycling of polyphenols takes place when the substrate is added to a solution containing tyrosinase and L-ascorbic acid. The current of the oxygen electrode detector in a flow-injection system with an immobilized tyrosinase reactor was significantly amplified when the carrier solution contained L-ascorbic acid, because the o-quinone compounds produced from substrates by the tyrosinase reaction are chemically reconverted to the original polyphenols by L-ascorbic acid. The establishment of a cyclic reaction of substrates in the enzyme reactor leads to amplification of oxygen consumption. The amplification factor increased with decreasing substrate concentration and was found to be larger than 100 when the substrate concentration was below 1 x lo-' M. The detection limits of polyphenols (catechol, r_.-dopa, dopamine, noradrenaline and adrenalin) were 1O-7-1O-g M in the presence of 1 X 10e3 M L-ascorbic acid in the carrier (pH 6.5, flow-rate 2.5 ml mm-').