Temperature‐dependent release of volatile organic compounds of eucalypts by direct analysis in real time (DART) mass spectrometry

Abstract

A method is described for the rapid identification of biogenic, volatile organic compounds (VOCs) emitted by plants, including the analysis of the temperature dependence of those emissions. Direct analysis in real time (DART) enabled ionization of VOCs from stem and leaf of several eucalyptus species including E. cinerea, E. citriodora, E. nicholii and E. sideroxylon. Plant tissues were placed directly in the gap between the DART ionization source skimmer and the capillary inlet of the time-of-flight (TOF) mass spectrometer. Temperature-dependent emission of VOCs was achieved by adjusting the temperature of the helium gas into the DART ionization source at 50, 100, 200 and 300 degrees C, which enabled direct evaporation of compounds, up to the onset of pyrolysis of plant fibres (i.e. cellulose and lignin). Accurate mass measurements facilitated by TOF mass spectrometry provided elemental compositions for the VOCs. A wide range of compounds was detected from simple organic compounds (i.e. methanol and acetone) to a series of monoterpenes (i.e. pinene, camphene, cymene, eucalyptol) common to many plant species, as well as several less abundant sesquiterpenes and flavonoids (i.e. naringenin, spathulenol, eucalyptin) with antioxidant and antimicrobial properties. The leaf and stem tissues for all four eucalypt species showed similar compounds. The relative abundances of methanol and ethanol were greater in stem wood than in leaf tissue suggesting that DART could be used to investigate the tissue-specific transport and emissions of VOCs.

Emissions of volatile organic compounds from heated needles and twigs of Pinus pumila

“…The dominating monoterpenes ((C 5 H 8 ) 2 ) were α-pinene, camphene, β-pinene, Dlimonene, 3-carene, neo-allo-ocimene, and santene, accounting for 59.60%, 14.25%, 11.93%, 5.63%, 2.88%, 2.02%, and 1.63% of the total terpenoids, respectively (Table 2). Similar results were reported in VOC emitted from the heated Rosmarinus officinalis plants (Chetehouna et al 2009), the drying sawdust of Norway spruce (Picea abies) (Granström 2003), and eucalypt at different high temperatures (Maleknia et al 2009a(Maleknia et al , 2009b. The components of terpenoid VOC are not the same with the compositions of volatile oils, that is to say, there are large amount of sesquiterpenes (C 5 H 8 ) 3 and oxygen-monoterpenes in volatile oils (Jin et al 1994).…”

“…Terpenoid emissions are in close relation with temperature (Maleknia et al 2009b). The terpenoid emissions increase with an increase in temperature, until temperature reaches a threshold.…”

“…Zhao et al (2004) reported that the terpenoid emissions rates from Larix gmelini, P. Koraiensis, under standard conditions (T=303K, PAR=1000 μmol⋅m -2 ⋅s -1 ) in Helongjiang Province only were 0.05 μgC⋅g -1 ⋅h -1 , 0.30 μgC⋅g -1 ⋅h -1 respectively. The best interpretation for lower terpenoid emissions under natural conditions and higher terpenoid emissions under high temperature conditions is that terpenoids have a close relationship with temperature (Maleknia et al 2009b). It can be inferred that a large amount of terpenoids will be emitted when fuels get heat from surrounding environment.…”

“…Most ORIGINAL PAPER recently, the study on terpenoid emissions from heated vegetation has provided a good method to explore the mechanism how volatiles oils affect fire behaviours (Chetehouna et al 2009). As the boiling points of main volatile oils are very low (Table 1), a large amount of terpenoids will be emitted from plants under heated conditions, i.e., before the pyrolysis of plant tissue (Granström 2003;Maleknia et al 2009aMaleknia et al , 2009b. The large amount and very flammable gases would have strong effects on fire propagation.…”

Direct analysis in real time (DART) mass spectrometry of nucleotides and nucleosides: elucidation of a novel fragment [C5H5O]+and its in-source adducts

“…The temperature of helium gas used in the DART ion source was 200 or 250°C, a temperature that is suitable for pyrolysis of nucleotides [23]. Pyrolysis of analytes at a sufficiently high-temperature in DART mass spectrometry has been previously reported [24,25]. In our experiments, with the elevation of the helium stream temperature from 200 to 250°C, the production of 1 increased significantly, indicating that such fragmentation was indeed temperature-dependent.…”