Monoterpene Chemical Speciation with High Time Resolution Using a FastGC/PTR-MS: Results from the COV3ER Experiment on Quercus ilex

Abstract

<jats:p>Monoterpenes (MTs) represent an important family of biogenic volatile organic compounds (BVOCs) in terms of amount and chemical diversity. This family has been extensively studied using gas chromatography (GC) and proton transfer reaction-mass spectrometry (PTR-MS). Upon recent advances with Fast Gas Chromatography (FastGC), it was also commercialized with proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS) instruments. The combination of both techniques showed promising results in the near real-time separation of isomers, with the need of further improvements. In this study, a FastGC prototype was coupled to a conventional PTR-MS (PTR-QuadMS). Extensive laboratory experiments were performed, in order to test the system’s performance and to optimize its operational parameters for MT separation. The detection limit was determined to be around 0.8–1.7 ppbv, depending on the MT. The system was afterwards deployed during a three-week field campaign in a mixed holm oak (Quercus ilex) forest known for its important MT emissions. MTs were measured in the incoming and the outgoing air of dynamic enclosures installed on the branches of four different trees. Three chemotypes of holm oak trees could be distinguished showing consistently different proportions of the emitted MTs throughout the measurement campaign: pinene-type, myrcene-type and limonene-type. Measurements showed a systematic diel variation in emissions typical of light and temperature-dependent, de novo-synthesized VOCs. The results demonstrated the feasibility of the FastGC/PTR-MS system for continuous measurements from dynamic chambers in the field, whereas further improvements would be necessary to lower the detection limit for ambient air measurements.</jats:p>

An Improvement of SPME-Based Sampling Technique to Collect Volatile Organic Compounds from Quercus ilex at the Environmental Level

“…In particular, the DBSS allowed identifying the typical compounds emitted by Q. ilex. Indeed, qualitative MTs identification carried out in our study is consistent with results reported in previous experiments conducted on the same species both in pots and in field conditions [49,50,65,66]. In all sampling points, α-pinene, α-thujene, β-pinene, sabinene and d-limonene were the most abundant compounds emitted by Q. ilex [5,46,48], which represented about 65-80% of the total detected monoterpenes.…”

“…In all three sampling points, the only terpenes identified were monoterpenes and monoterpenoids (MTs), while no sesquiterpenes or other BVOCs were detected. Indeed, the Q. ilex BVOC emission pattern is mainly characterized by monoterpenes [45][46][47][48][49][50]. In the first sampling point, there were no differences in MTs collected using the two sampling techniques (DBSS and static sampling).…”

Insights into the Intraspecific Variability of the above and Belowground Emissions of Volatile Organic Compounds in Tomato

“…Plant VOCs also affect the food web by serving as cues for herbivores to localize their host plants, or as a food source for microbes in both the rhizosphere and phyllosphere [8][9][10]. Owing to their multiple roles in plant ecology and advances in the real-time detection of trace gases (e.g., [11,12]), the study of VOCs that are emitted by crop plants has received increasing attention in the field of agroecology and crop protection. Provided that the emitted VOCs can be unequivocally identified and quantitatively measured without disturbing the actual physiological status of the plants, the online monitoring of the volatile metabolome represents a valuable non-invasive tool for early stress detection and survey of variation in plant fitness and phenology [13][14][15].…”

Environmental Factors Affecting Monoterpene Emissions from Terrestrial Vegetation

“…For C. japonica, the emission rates of α-Pinene, β-Pinene, and α-Phellandrene accounted for 61%; for C. obtusa, α-Pinene, β-Pinene, and D-Limonene accounted for 63%; and for P. densiflora, α-Pinene, β-Pinene, and β-Myrcene accounted for 95% of the total monoterpene. Similarly, emissions of α-pinene, sabinene, β-pinene, myrcene, and limonene from Q. ilex L. are strongly affected by light intensity and leaf temperature [75,79,[89][90][91]. Despite knowledge about the light intensity-monoterpene correlation, the effect of light on the emissions from non-woody plant species needs further investigation.…”