Biosensors for L-malate and L-lactate based on solid binding matrix

Biosensors for the selective determination of L-lactate and L-malate in win e based on robust solid composite transducers are presented. Transducers co mprised a solid binding matrix having hydrophobic skeleton, e.g. 2-hexadeca none, graphite and NAD(+), The enzymes, L-malate or L-lactate dehydrogenase and diaphorase, were placed onto the transducer surface and covered by a d ialysis membrane, which substantially reduced interferences derived from ea sily oxidable compounds, e.g. polyphenols, of wine. Hexacyanoferrate(III) w as used as a mediator. The electrode responses were linear up to 1.1 mM for L-malate and 1.3 mM for L-lactate, The detection limit was at about 10 mu M. The biosensors showed an excellent long-term stability, after five month s storage at room temperature, the L-malate sensor exhibited almost 100% an d L-lactate 90% of the initial sensitivity, A multisensor composed of two e nzyme electrodes allowing a simultaneous determination of L-malate and L-la ctate was also constructed, The results obtained from the determination of both acids in wine samples by biosensors were in a good agreement with thos e obtained by liquid chromatography. (C) 1999 Elsevier Science B.V. All rig hts reserved.