Quantitative determination of sotolon, maltol and free furaneol in wine by solid-phase extraction and gas chromatography–ion-trap mass spectrometry

Abstract

A method for the analytical determination of sotolon [4,5-dimethyl-3-hydroxy-2(5 H)-furanone], maltol [3-hydroxy-2-methyl-4 H-pyran-4-one] and free furaneol [2,5-dimethyl-4-hydroxy-3(2 H)-furanone] in wine has been developed. The analytes are extracted from 50 ml of wine in a solid-phase extraction cartridge filled with 800 mg of LiChrolut EN resins. Interferences are removed with 15 ml of a pentane–dichloromethane (20:1) solution, and analytes are recovered with 6 ml of dichloromethane. The extract is concentrated up to 0.1 ml and analyzed by GC–ion trap MS. Maltol and sotolon were determined by selected ion storage of ions in the m/ z ranges 120–153 and 79–95, using the ions m/ z 126 and 83 for quantitation, respectively. Furaneol was determined by non-resonant fragmentation of the m/ z 128 mother ion and subsequent analysis of the m/ z 81 ion. The detection limits of the method are in all cases between 0.5 and 1 μg l −1, well below the olfactory thresholds of the compounds. The precision of the method is in the 4–5% range for levels in wine around 20 μg l −1. Linearity holds at least up to 400 μg l −1, and is satisfactory in all cases. The recoveries of maltol and sotolon are constant (70 and 64%, respectively) and do not depend on the type of wine. On the contrary, in the case of furaneol, red wines show constant and high recoveries (97%), while the recoveries on white wines range between 30 and 80%. Different experiments showed that this behavior is probably due to the existence of complexes formed between furaneol and sulphur dioxide or catechols. Sensory experiments confirmed that the complexed forms found in white wines are not perceived by orthonasal olfaction, and that the furaneol determined by the method can be considered as the free and odor-active fraction.