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Am. J. Enol. Vitic. 48:4:428-432 (1997)
Copyright © 1997 by the American Society for Enology and Viticulture.
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A New Approach to Dialysis in Sequential Injection Systems: Spectrophotometric Determination of L(+)-Lactate in Wines

Alberto N. AraÚJO 1, José L.F.C. Lima 1, M. Lúcia M.F.S. Saraiva 1, and Elias A.G. Zagatto 2

1 CEQUP/Physical-Chemistry De- partment, Faculty of Pharmacy, University of Porto, 4050 Porto (Portugal)
2 Analytical-Chemistry Department, Center of Nuclear Energy in Agriculture, University of São Paulo, Piracicaba SP (Brazil).

Isaraiva{at}mail.ff.up.pt

A sequential injection analysis (SIA) system for the spectrophotometric determination of L(+)-lactate using lactate oxidase/peroxidase was developed and applied to wine analysis. It incorporates a dialysis unit between the pump and the selecting valve to provide on-line dilution and interference minimization of the sample matrix. A volume of 100 µL of carrier solution trapped in one channel of the dialysis unit, acts as donor and acceptor solution. With an assay cycle of 262 seconds, the system allows a sample throughput of 14 samples per hour and yields precise results (rsd < 2%). Peroxidase (0.0512 IU) and 0.0384 IU of lactate oxidase promote the conversion of L(+)-lactate in 160 µL of sample, allowing its determination within the 0.25 to 2.5 g/L range. A detection limit of 0.074 g/L was calculated. Results are in good agreement with those obtained with the conventional method (Boehringer UV-Kit).

Key words: sequential injection analysis (SIA), L(+)-lactate, wine

Submitted on December 12, 1996






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Copyright © 1997 by the American Society for Enology and Viticulture.