Sampling of volatiles in closed systems: a controlled comparison of three solventless volatile collection methods

Authors: Alborn, Hans; Bruton, Robert; Beck, John

Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2021
Publication Date: 8/20/2021
Publication URL: https://handle.nal.usda.gov/10113/7589616
Citation: Alborn, H.T., Bruton, R.G., Beck, J.J. 2021. Sampling of volatiles in closed systems: a controlled comparison of three solventless volatile collection methods. Journal of Chemical Ecology. 47:930-940. https://doi.org/10.1007/s10886-021-01306-6.
DOI: https://doi.org/10.1007/s10886-021-01306-6

Interpretive Summary: In natural and agricultural systems, the interactions among plants, insects, and microbes are often governed by chemical odors (chemical communication). To help detect and investigate these interactions there is a continuous need for new and improved collection and analyses techniques. Studies led by USDA-ARS scientists at the Center for Medical, Agricultural, and Veterinary Entomology, Chemistry Research Unit, in Gainesville, FL used a standardized blend of odors to evaluate three solventless collection and analyses techniques: solid phase microextraction (SPME), solid phase dynamic extraction (SPDE), and an in-house designed thermal desorption system. The results indicated that related qualitative and quantitative differences could be correlated with adsorbent sampling capacity and structural bias, but most of the variations were better explained by factors such as gas phase equilibrium (the chemical odors in the air) and sampling volumes. The discovered strengths and weaknesses for each system were used to provide guidance for selection of techniques for natural and agricultural chemical communication applications.

Technical Abstract: Complex inter-organismal communication among plants, insects, and microbes in natural and agricultural ecological systems is typically governed by emitted and perceived semiochemicals. To understand and ultimately utilize the role of volatile semiochemicals in these interactions, headspace volatiles are routinely collected and analyzed. Numerous collection systems are available (e.g., static or dynamic; adsorption or absorption) where the choice of technique should be dependent upon the plant, insect, or microbial ecological system studied, the information sought, and the limitations of each method. Within these constraints, it remains necessary that each method detects and provides the accurate in situ, or in vitro, volatile profile of the studied system. Herein, we analyzed and compared the pros and cons of three solventless, thermal desorption systems (SPME, Tenax/cold trap, SPDE) using a synthetic standard blend of compounds mimicking a simple natural blend (benzaldehyde, b-caryophyllene, (Z)-3-hexenol, 6-methyl-5-hepten-2-one, and limonene). Direct splitless injection and Super Q collections of the standard blend were used as controls. The results indicated that related qualitative, as well as quantitative differences, could be correlated with adsorbent sampling capacity and structural bias. The results for Tenax/cold trap and SPDE also were affected by sampled headspace volumes. All solventless techniques exhibited high analytical reproducibility, with SPME and SPDE providing ease of use, low cost, and minimal instrument modifications. The more complex Tenax/cold trap technique provided higher collection efficiency. Using these results, we provide guidance for technique selection for chemical communication applications