Quantifying sesquiterpene and oxygenated terpene emissions from live vegetation using solid-phase microextraction fibers

Biogenic terpenes play important roles in ecosystem functioning and atmospheric chemistry. Some of these compounds are semi-volatile and highly reactive, such as sesquiterpenes and oxygenated terpenes, and are thus difficult to quantify using traditional air sampling and analysis methods. We developed an alternative approach to quantify emissions from live branches using a flow through enclosure and sample collection on solid-phase microextraction (SPME) fibers. This method allows for collection and analysis of analytes with minimal sample transfer through tubing to reduce the potential for losses. We characterized performance characteristics for 65 microm polydimethylsiloxane-divinylbenzene (PDMS/DVB) fibers using gas chromatography followed by mass spectrometry and optimized experimental conditions and procedures for field collections followed by laboratory analysis. Using 10-45 min sampling times and linear calibration curves created from mixtures of terpenes, emissions of methyl chavicol, an oxygenated terpene, and an array of sesquiterpenes were quantified from a Ponderosa pine branch. The detection limit was 4.36 pmol/mol (ppt) for methyl chavicol and 16.6 ppt for beta-caryophyllene. Concentrations determined with SPME fibers agreed with measurements made using proton transfer reaction mass spectrometry (PTR-MS) within the estimated error of the method for well calibrated compounds. This technique can be applied for quantification of biogenic oxygenated terpene and sesquiterpene emissions from live branches in the field.