Honey is a very complex, biologically extremely valuable product of honeybees.  It consists of hundreds of components, most of those are various sugar derivatives.  Detailed analysis of honey is a formidable task, especially that many of the components are unstable and/or don't behave well in chromatography-MS conditions.  Quality of honey is a very important safety and market issue both, so reliable characterization of honey samples is an essential requirement.NMR spectroscopy has the unique advantage of being naturally quantitative and non-discriminative.  Sample preparation is usually simple, while the measurement is robust and highly reproducible.  Mixture analysis by NMR is often done by using 1H-NMR, however, for complex biomaterials, such as honey, 13C-NMR is much more suitable.  Given the extended chemical shift regime (up to 200 ppm) and the singlet nature of each carbon resonance, both dispersion and resolution are superior to that available in proton.  In addition, 13C chemical shifts are better correlated with structural features making identification of components more feasible.Detection of natural abundance 13C-NMR is of low sensitivity by nature, but recent developments in optimized cryoprobe technology make this approach truly competitive.  In our laboratory quantitative 13C-NMR of a typical honey sample can be run within an hour.  If only qualitative analysis is necessary the time required falls back to ten minutes or less.Using the resolving power of 13C-NMR we can distinguish the sugar components in-situ, without any separation or pre-treatment of the sample required;  the sample is studied in its natural condition.  In addition, large proportion of the additional components can be identified and analyzed quantitatively.  We have been looking at various honey samples of different season and/or different origin using cryo-13C-NMR.  The analysis of the data may include statistical methods, as well as direct comparative component analysis using efficient prediction tools and database information. The highly rich, quantitative information provided by cryoprobe-assisted 13C-NMR spectroscopy makes it a prime analytical tool for detailed analysis, identification of its origin, and for quality control of food and food ingredients, such as honey.

Honey analysis by high-sensitivity cryo-13C-NMR

244th National Meeting (2012)

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