Volatome analysis approach for the taxonomic classification of tree exudate collection using Proton Transfer Reaction Time of Flight Mass Spectrometry

Natural resins exude from trees as viscous liquids, which subsequently harden by evaporation and/or oxidation. Their compositions and textures are complex and vary during the solidification processes, producing a typical volatile fragrant fraction. Many techniques have been applied to the study of resins in order to obtain considerable chemical information but no exploratory work has been conducted using Proton Transfer Reaction Time of Flight Mass Spectrometry (PTR-ToF-MS). For this reason its potential to rapidly obtain the Volatiles Organic Compounds (VOCs) mass profiles of several natural resins has been tested. A Partial Least Squares Discriminant Analysis (PLSDA) have been performed to classify all samples based on their species, family or order on the basis of the VOCs emission profiles of 31 natural resins derived from different tree species. The sensitivities and specificities obtained were higher than 95% whilst a correct classification was higher for family (94.23% on 7 classes) and order (94.12% on 6 classes), than that of species (89.06% on 31 classes). Finally confusion matrices based on PLSDA models were produced to observe and draw conclusions about non-correct classifications. In our study we successfully determined the volatile profiles for 31 different tree natural resins assessing the possibility of correctly identify the taxonomic position of the trees by the analysis of their aromatic profiles. This preliminary study could lay down the bases for future studies on the VOC emissions of resins, by qualifying PTR-ToF-MS as a promising tool for a fast resin identification of complex matrix.