A novel fast gas chromatography method for higher time resolution measurements of speciated monoterpenes in air

Abstract

Abstract. Biogenic emissions supply the largest fraction of non-methane volatile organic compounds (VOC) from the biosphere to the atmospheric boundary layer, and typically comprise a complex mixture of reactive terpenes. Due to this chemical complexity, achieving comprehensive measurements of biogenic VOC (BVOC) in air within a satisfactory time resolution is analytically challenging. To address this, we have developed a novel, fully automated Fast Gas Chromatography (Fast-GC) based technique to provide higher time resolution monitoring of monoterpenes (and selected other C 9 -C 15 terpenes) during plant emission studies and in ambient air. To our knowledge, this is the first study to apply a Fast-GC based separation technique to achieve quantification of terpenes in ambient air. Three chromatography methods have been developed for atmospheric terpene analysis under different sampling scenarios. Each method facilitates chromatographic separation of selected BVOC within a significantly reduced analysis time compared to conventional GC methods, whilst maintaining the ability to quantify individual monoterpene structural isomers. Using this approach, the C 9 -C 15 BVOC composition of single plant emissions may be characterised within a 14.5 min analysis time. Moreover, in-situ quantification of 12 monoterpenes in unpolluted ambient air may be achieved within an 11.7 min chromatographic separation time (increasing to 19.7 min when simultaneous quantification of multiple oxygenated C 9 -C 10 terpenoids is required, and/or when concentrations of anthropogenic VOC are significant). These analysis times potentially allow for a twofold to fivefold increase in measurement frequency compared to conventional GC methods. Here we outline the technical details and analytical capability of this chromatographic approach, and present the first in-situ Fast-GC observations of 6 monoterpenes and the oxygenated BVOC (OBVOC) linalool in ambient air. During this field deployment within a suburban forest ∼ 30 km west of central Tokyo, Japan, the Fast-GC limit of detection with respect to monoterpenes was 4-5 ppt, and the agreement between Fast-GC and PTR-MS derived total monoterpene mixing ratios was consistent with previous GC/PTR-MS comparisons. The measurement uncertainties associated with the Fast-GC quantification of monoterpenes are ≤ 12 %, while larger uncertainties (up to ∼ 25 %) are associated with the OBVOC and sesquiterpene measurements.

Field measurements of biogenic volatile organic compounds in the atmosphere by dynamic solid-phase microextraction and portable gas chromatography-mass spectrometry

“…Chemical composition may be obtained by using conventional gas-chromatography methods, such as GC-FID and GCeMS, which allow for quantitation of terpene isomers with high sensitivity and specificity (Jones et al, 2014). Chemical ionization techniques together with direct mass spectrometric analysis are also commonly used, as they can produce high time resolution and high sensitivity, but the identification of some molecular species can be challenging without chromatographic separation (Kaser et al, 2013).…”

Optimization of a gas chromatographic unit for measuring BVOCs in ambient air

“…Detailed information regarding chemical composition may be obtained by conventional gas chromatographic methods (GC-FID or GC-MS), which can quantify individual terpene isomers (Jones et al 2014;Hopkins et al, 2011;Pankow et al 2012).…”

“…Ambient measurements taking advantage of gas chromatographic techniques usually report isoprene, α-pinene, β-pinene and limonene (Apel et al, 1999;Bouvier-Brown et al, 2009;Greenberg et al, 2004Greenberg et al, , 1999Hopkins et al, 2011;Mallet et al, 2016;Misztal et al, 2010;Saxton et al, 2007) as the major BVOCs. Only a few GC instruments have been optimized to 30 provide a larger speciation of monoterpenes (Pankow et al, 2012;Jones et al, 2014;Hakola et al, 2006Hakola et al, , 2017 and even https://doi.org /10.5194/amt-2019-224 Preprint. Discussion started: 11 July 2019 c Author(s) 2019.…”

“…CC BY 4.0 License. fewer can provide a large speciation of both monoterpenes and oxygenated monoterpenes (Jones et al, 2014;Pankow et al, 2012) (Table 1). Due to their high reactivity, monoterpenes and sesquiterpenes are delicate to quantify.…”

“…Amongst potential artefacts, ozonolysis of monoterpenes and sesquiterpenes within the sampling line may occur and the use of ozone scrubbers is recommended (Koppmann, 2007). Some scrubbers have already been used for BVOC measurement, such as copper tubes 10 coated by potassium iodide (KI) (Saxton et al, 2007) and thiosulfate scrubbers (Bouvier-Brown et al, 2007;Jones et al, 2014;Plass-Dülmer et al, 2002).…”