Chemiluminometric flow-injection method for determination of free l-malate in wine with co-immobilized malate dehydrogenase/NADH oxidase.
A flow-injection system with a co-immobilized malate dehydrogenase/reduced nicotineamide adenine dinucleotide (NADH) oxidase reactor and a chemiluminometer is described for the determination of free l-malate in wine. Malate dehydrogenase and NADH oxidase were co-immobilized on poly(vinyl alcohol) beads and packed into a stainless-steel column (5 cm x 4 mm i.d.). The hydrogen peroxide produced was detected chemiluminometrically via a luminol-hexacyanoferrate(III) reaction. The calibration graph was linear from 3 x 10(-7) M to 2.5 x 10(-4) M (the linear correlation coefficient was 0.9998); the detection limit (signal-to-noise ratio, 3) was 8 x 10(-8) M. The sample throughput was 30 h(-1) without carryover. The ractor was renewed every 2 weeks.
Kiba
N
N
Department of Applied Chemistry and Biotechnology, Faculty of Engineering, Yamanashi University, Kofu 400, Japan.
Inagaki
J
J
Furusawa
M
M