Quantification of L-Tartrate in Wine by Stopped-Flow Injection Analysis Using Immobilized D-Malate Dehydrogenase and Fluorescence Detection

A stopped-flow injection system with an immobilized enzyme reactor is proposed for the quantification of L-tartrate in wine. L-Tartrate was oxidized using the secondary activity of D-malate dehydrogenase (D-MDH), which was immobilized on aminopropyl-controlled pore glass beads with glutaraldehyde. NADH produced by D-MDH reaction was detected fluorometrically at 460 nm (excitation at 340 nm). The calibration graph was linear over the range 0.01 - 1.20 mM with a correlation coefficient of 0.999 when the stopped-time was 180 s. The relative standard deviation for ten measurements was 0.81% at the 1.0 mM level. The sample throughput was 12 h-1. The results obtained by the proposed method and an HPLC method are in good agreement with each other. The D-MDH reactor was stable for one month when used daily under the optimal conditions.