Aqueous two-phase systems (ATPS) are an important technique for the extraction and purification of bio-molecules. In aqueous media, many pairs of solutes can be used to prepare ATPS and, in spite of their interest, scarce attention has been given to the use of mono- and disaccharides. In this context, this work addresses the use of acetonitrile and carbohydrates to prepare aqueous two-phase systems and their application in the partition of vanillin. The phase diagrams were determined at 298 K and the impact of the carbohydrate structure on the liquid-liquid demixing was evaluated. Besides high purity carbohydrates, commercial food grade sugars were also tested and are shown to be able to form ATPS. Their impurities affect, however, the phase separation and tend to reduce the two-phase region. The studied ATPS were investigated for the extraction of vanillin that favorably partitions towards the acetonitrile-rich phase with partition coefficients higher than 3.0 and recoveries up to 91% attained in a single step. (c) 2012 Elsevier B.V. All rights reserved.