Flow Injection Determination of Lactate Using Immobilized Lactate Dehydrogenase Enzyme with Tris(2,2′-Bipyridyl)Ruthenium(III) Chemiluminescence Detection

A flow-injection procedure is reported for the determination of L-lactate based on its enhancement on tris(2,2 '-bipyridyl)ruthenium(III) chemiluminescence in the presence of reduced nicotinamide adenine dinucleotide produced using immobilized lactate dehydrogenase. The calibration graph was linear between 4 and 50x10(-7)molL(-1) (r(2)=0.9998) with relative standard deviation from 1.6 to 3.0% (n=4). The limit of detection was 1x10(-7)molL(-1) with a sample throughput of 60 per hour. The effect of common organic compounds and metal ions was studied. The immobilized lactate dehydrogenase exhibited good operational activity at 37 degrees C for one week and storage stability at 4 degrees C over a period of 10 weeks. The method was applied to blood serum, and the results were in good agreement with those obtained by a conventional spectrophotometric method with no significant difference at the 95% confidence level.