CYCLIC ENZYMATIC DETERMINATION OF L-LACTATE BY DIFFERENTIAL PH MEASUREMENT

An electrochemical procedure for the analysis of L-lactate based on the lactate dehydrogenase/lactate oxidase reaction cycle has been developed and applied in whole blood and wine. The reaction of lactate with lactate oxidase produces pyruvate, which is the substrate, at physiological pH, of the enzyme lactate dehydrogenase. This enzyme, in the presence of NADH, converts pyruvate to lactate consuming H+ An automated software controlled differential pHmeter was used for H+ detection and the Delta pH measured was correlated to the lactate concentration present in the sample. Lactate was measured in the range 0.4-20 mmol/L with a detection limit of 0.2 mmol/L. Recovery studies have been carried out to evaluate the effect of blood and wine matrices on lactate determination. The recovery was between 94 and 104% in blood and 93 and 104% in wine. Analysis of lactate in blood and wine samples has been carried out. Comparison with a reference spectrophotometric procedure has been reported and discussed.