ANALYSIS OF THE ENANTIOMERIC PURITY OF LACTATE WITH AN ENZYME ELECTRODE

Lactate oxidase (EC 1.1.3.2) catalyzes the oxidation of lactate to pyruvate with the concurrent reduction of oxygen to hydrogen peroxide- An oxygen electrode (-650 mV vs Ag/AgCl) was prepared with an immobilized lactate oxidase membrane. L-Lactate was determined by monitoring the decrease in oxygen concentration from the enzyme reaction. The initial rate of decrease was proportional to the concentration in the range tested (70-340 muM, RSD 3.2%, det. limit 6 muM). Recovery from a spiked placebo was 102% and D-lactate did not give a significant response. Results from testing two pharmaceutical products indicated that one was manufactured with raceMiC lactate (L-lactate 49.4% of label claim) and one was manufactured with enantiomerically pure L-lactate (L-lactate 102% of label claim).