FLOW-INJECTION METHOD FOR THE POLAROGRAPHIC-DETERMINATION OF L-LACTATE USING AN IMMOBILIZED ENZYME REACTOR

A sensitive flow injection system for L-lactate with polarographic detection is described. The system mainly utilizes saturated dissolved oxygen in samples for enzymatic reactions to convert L-lactate and oxygen to pyruvate and hydrogen peroxide; and then, any excess amount of dissolved, electroreducible oxygen which is not consumed in the enzymatic reaction can be retarded by an ODS-column to separate it from the pyruvate and hydrogen peroxide. After that, both the pyruvate and hydrogen peroxide are measured by the polarographic method using a static mercury drop electrode. The enzyme, lactate oxidase, was covalently immobilized on Chitopearl(R) composed of chitosan, and packed into a reactor. The detection limit under this system was 9.9 x 10(-6) M and the relative standard deviation at 2.0 x 10(-4) M L-lactate was 2.8%.