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Amperometric flow‐injection determination of citric acid in food using free citrate lyase and co‐immobilized oxalacetate decarboxylase and pyruvate oxidase
Author(s) -
Matsumoto Kiyoshi,
Tsukatani Tadayuki,
Okajima Yuko
Publication year - 1995
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.1140070604
Subject(s) - chemistry , atp citrate lyase , detection limit , citric acid , amperometry , chromatography , thiamine pyrophosphate , flavin adenine dinucleotide , flow injection analysis , hydrogen peroxide , glucose oxidase , enzyme , biochemistry , cofactor , electrode , citrate synthase , electrochemistry
Abstract A flow‐injection analytical system for the determination of citrate in food has been developed. Citrate lyase, oxalacetate decarboxylase, and pyruvate oxidase were used, and the latter two enzymes were co‐immobilized. Hydrogen peroxide, which was produced by three enzyme reactions, was monitored amperometrically with a platinum electrode. The carrier solution used was 0.1 M phosphate buffer (pH 7.0) containing 10 mM MgCl 2 , 80μM thiamine pyrophosphate (TPP), and 10μM flavine adenine dinucleotide (FAD). The detection limit was 0.02mM, and the range of determination was 0.1‐1.0 mM. The relative standard deviation was 1.23% for 10 successive determinations at the 0.5 mM level. The determination frequency was about 15 tests per hour. The present system was applied to the determination of citrate in several fruits. The results showed good agreement with those obtained using a conventional method (F‐kit method).