DETERMINATION OF LACTATE BY THE INTRINSIC FLUORESCENCE OF LACTATE OXIDASE

A fluorimetric method for the determination of lactate based on its en zymatic reaction with lactate oxidase (LOx) is proposed. The method re lies on the relationship between the decrease in the enzyme intrinsic fluorescence during the reaction and the lactate concentration, which is shown to be the result of a primary internal filter effect on the e nzyme by the pyruvate formed in the reaction. A mathematic model for p redicting the effect of some parameters on the magnitude of the analyt ical signal was developed that provided good correlations with the exp erimental results. Ah those experimental variables affecting the analy tical signal were optimized. Under the best possible conditions, the m ethod features a linear determination range from 4 to 25 mg/l lactate and a reproducibility of 3.5%, as the relative standard deviation. The proposed method allows lactate and pyruvate to be determined simultan eously. The predictions of the proposed model were also quite consiste nt with the experimental results obtained for synthetic samples contai ning both species.