Numerous analytical methods have been developed during the past decades and have proven to be extremely efficient, for instance, in the case of single, high purity compounds for the measurements of concentration and/or structure elucidation. However, real-world applications often require the characterization of complex mixtures containing tens to thousands of compounds, such as biofluids, food matrices, industrial products, etc. The complete characterisation of such mixtures would be tedious, not to say impossible in the case of mixtures containing hundreds of compounds, and certainly unfeasible for monitoring purposes. In fact, one can concentrate on one or a few molecules which entail the non-negligible issue of the choice of the molecules of interest, and therefore require an a priori knowledge. Nevertheless this approach usually requires molecular separation and purification, which is time, money and human resource consuming.
In contrast the Nuclear Magnetic Resonance (NMR) fingerprinting aims at establishing a holistic approach: the mixture is submitted to the NMR experiment as a whole. A simple quantification of the major compounds, which are characterised by one or several signals in the NMR spectrum, can be performed. This type of analysis is particularly attractive for several reasons: it is non-destructive, non selective and cost effective; requires little or no sample pre-treatment; uses small amounts of organic solvents or reagents; and typically takes only a few minutes per sample.
The spectra of complex mixtures show hundreds of signals, coming from numerous molecules. This and the overlap of signal make it difficult to extract information, either visually or by simple processing of the data. The most effective way to analyse these holistic profiles is by using chemometric tools which enable the visualisation of the data in a reduced dimension and the classification of the samples into established classes based on inherent patterns in a set of spectral measurements. Moreover, these techniques also allow to trace the NMR spectral variables responsible of this classification, and thus, identify molecular markers of interest.
Isotopic measurements such as Isotopic Ratio Mass Spectroscopy (IRMS) or Site-specific Natural Isotopic Fractionation (SNIF-NMR) provide few variables, but these contain unique information on geographical origin and metabolic or production pathways. Thus, isotopic measurements provide complementary data to NMR fingerprinting.JRC.I.5-Physical and chemical exposure
