Analysis of plant raw materials and extracts applying various vibrational spectroscopy techniques – possibilities and limitations

New methods using MIR, NIR and Raman spectroscopy in combination with various chemometric algorithms are presented which allow monitoring numerous plant samples very efficiently within a short time. Today portable FT-IR spectrometers are available which only need sample amounts of a few microliters or milligrams. In most cases, the measurements can be performed directly and non-destructively on the individual plant tissues or plant extracts. Generally, with IR and Raman spectroscopic techniques spectra are obtained which present characteristic key bands of individual plant components. These bands provide important information about the chemical composition of the investigated samples. Based on such markers spectroscopic analyses in principle allow the discrimination of different species, and even to classify chemotypes among the same species. Combination of vibrational spectroscopy and hierarchical cluster analysis provides a fast, easy and reliable method for chemotaxonomic characterization. The ability to rapidly monitor various plant components makes it possible to efficiently select high-quality single plants from wild populations as well as progenies of crossing experiments. Furthermore, the vibrational spectroscopic methods can also be used by the processing industry in order to perform fast quality checks of incoming raw materials as well as continuous controlling of production processes.