Analytical and Bioanalytical Chemistry

, Volume 387, Issue 6, pp 2297–2305

Fluorescent sensing layer for the determination of L-malic acid in wine

  • Félix Gallarta
  • Francisco Javier Sáinz
  • Cecilia Sáenz
Original Paper

DOI: 10.1007/s00216-006-1027-8

Cite this article as:
Gallarta, F., Sáinz, F.J. & Sáenz, C. Anal Bioanal Chem (2007) 387: 2297. doi:10.1007/s00216-006-1027-8

Abstract

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 (λexc = 340 nm, λem = 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 [sr(%)≈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.

Keywords

Sensing layerL-Malate dehydrogenaseSol-gelL-MalateWines

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Félix Gallarta
    • 1
  • Francisco Javier Sáinz
    • 1
  • Cecilia Sáenz
    • 1
  1. 1.Laboratory of Analytical Chemistry, Department of ChemistryUniversity of La RiojaLogroñoSpain