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

Quantitative isotopic 13C‐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 13C/12C ratio of a molecule, isotopic 13C‐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.