Problems of the Qualitative and Quantitative Analysis of Plant Volatiles

Resumo

Strategies for the analysis of plant volatiles have changed significantly over the past 15–20 years due to the introduction of new approaches to sample preparation and analysis, including those initially developed for other areas and currently applied to the analysis of plant metabolites. Any analysis of plant substances consists of two phases. The first phase includes plant material collection, primary processing, conservation, storage, and extraction to prepare samples for research. The second phase is the analysis itself by various chromatographic, spectral, and/or hybrid (hyphenated) techniques. Most scientific publications focus their attention on the second phase, and the first remains “behind the scenes,” although it is in the first phase that the biomaterial experiences significant transformations. It is impossible to correctly and adequately evaluate the ultimate result of a study without taking these transformations into account. Specific difficulties arise in both phases, and they are reviewed in this paper. The wide distribution of modern chromatographic instruments equipped with sophisticated software allows a significant portion of an experiment to be performed automatically. However, one should realize that the improvement of experimental techniques does not change the basics of a method, and, therefore, does not eliminate its intrinsic limitations. To avoid fallacies in the publication of the results, all the experimental data obtained in the automatic mode should be subjected to an impartial revision by the experimenter with regard to all known limitations inherent in methods used for separation and detection of components. In order to correctly interpret experimental results, one should know the entire history of samples under investigation; thus, it is necessary to document carefully all manipulations with plant material from the collection of raw materials till the final sample preparation. Only with this proviso the study can be expected to provide meaningful results.