Procedure for the isolation of vanillin from vanilla extracts prior to isotopic authentication by quantitative C-13-NMR

Quantitative isotopic C-13-NMR at natural abundance recently became a new tool for the authentication of natural flavours. In contrast to isotopic-ratio mass spectrometry, which yields the global C-13/C-12 ratio of a molecule, isotopic C-13-NMR allows the determination of isotopic ratios of each spectroscopically differentiable carbon site. Since it requires a significant amount of the purified analyte, an optimized vanillin isolation procedure is presented here. It involves an accelerated solvent extraction of beans, a fat removal step and a subsequent medium-pressure isolation of the vanillin peak on a reusable reverse-phase column, using mostly water as a mobile phase (97%). The overall recovery from the bean extract is 90%. The procedure was automated as much as possible and checked against the risk of isotopic fractionation. The overall protocol was demonstrated to be suitable for isotopic measurements. Copyright (C) 2010 John Wiley & Sons, Ltd