Fluorescencent sensing layer for the determination of L-malic acid in wine.
- Gallarta, F. 1
- Sáinz, Francisco Javier. 1
- Sáenz, C. 1
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1
Universidad de La Rioja
info
ISSN: 1618-2642
Año de publicación: 2007
Volumen: 387
Número: 6
Páginas: 2297-2305
Tipo: Artículo
Otras publicaciones en: Analytical and Bioanalytical Chemistry
Resumen
An enzymatic method for determining L-malic acid in wine based on an L-malate sensing layer with nicotinamide adenine dinucleotide (NAD+), L-malate dehydrogenase (L-MDH) and diaphorase (DI), immobilized by sol-gel technology, was constructed and evaluated. The sol-gel glass was prepared with tetramethoxysilane (TMOS), water and HCl. L-MDH catalyzes the reaction between L-malate and NAD+, producing NADH, whose fluorescence (λ exc∈=∈340 nm, λ em∈=∈430 nm) could be directly related to the amount of L-malate. NADH is converted to NAD+ by applying hexacyanoferrate(III) as oxidant in the presence of DI. Some parameters affecting sol-gel encapsulation and the pH of the enzymatic reaction were studied. The sensing layer has a dynamic range of 0.1-1.0 g/L of L-malate and a long-term storage stability of 25 days. It exhibits acceptable reproducibility [s r(%)≈10] and allows six regenerations. The content of L-malic acid was determined for different types of wine, and polyvinylpolypyrrolidone (PVPP) was used as a bleaching agent with red wine. The results obtained for the wine samples using the sensing layer are comparable to those obtained from a reference method based on UV-vis molecular absorption spectrometry, if the matrix effect is corrected for. © Springer-Verlag 2007.