Flow injection analysis of L-lactic acid using an enzyme-polyion complex-coated electrode as the detector

The concentration of L-lactic acid was determined by a combination of flow injection analysis with amperometric enzyme sensor detection. The enzyme sensor was prepared by immobilizing lactate oxidase in a layer of polyion complex consisting of poly-L-lysine and poly(4-styrenesulfonate). The sensor-based system can be used for the determination of L-lactate concentration up to 6 mM with a sampling rate of 120 h(-1), and is stable for 8 weeks after 1000 L-lactate injections. The permselectivity of the polyion complex matrix is effective for reducing the response from electrochemical interferents such as L-ascorbic acid, uric acid and acetaminophen.