IMMOBILIZATION OF LACTATE OXIDASE IN A POLY(VINYL ALCOHOL) MATRIX ON PLATINIZED GRAPHITE-ELECTRODES BY CHEMICAL CROSS-LINKING WITH ISOCYANATE

A new method for development of an electrochemical sensor based on lactate oxidase is described. Platinized spectroscopic-grade graphite electrodes were modified by chemically cross-linking L-lactate oxidase from Pediococcus species into a poly(vinyl alcohol) network through reaction with a tri-isocyanate. The immobilized enzyme exhibits high activity and long-term stability. The sensor provides a linear response to L-lactate over a concentration range of 2 x 10(-5)-4 x 10(-3) M and a sensitivity of 1.71-mu-A.1.mmole-1. The response time of the sensor is 10-45 sec and the detection limit is 10-mu-M. Stable response to the substrate was obtained over a period of 3 months. The new sensor was also used for the analysis of some dairy products without any special pretreatment.