Submitted to: MethodsX
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2018
Publication Date: 6/28/2018
Citation: Faust, D.R., Liebig, M.A. 2018. Effects of storage time and temperature on greenhouse gas samples in Exetainer vials with chlorobutyl septa caps. MethodsX. https://doi.org/10.1016.j.mex.2018.06.016.
Interpretive Summary: Greenhouse gas (GHG) samples are obtained in various ecosystems (e.g., agroecosystems) using static chamber methods to determine carbon and nitrogen dynamics and potential contributions to climate change. While guidance exists for many aspects of sampling and measuring GHGs, guidance on proper storage of GHG samples is lacking. This study examined effects of storage time and temperature on “low” and “high” concentrations of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in certified standards. Storage temperatures were laboratory workbench at ambient room temperature, incubator set to 25°C, walk-in cooler set to 4°C, and freezer at -10°C. Storage times were 3, 7, 14, 28, and 84 days. Results indicated storage of GHG samples up to 28 days at any storage temperature is appropriate. Storage of samples for 84 days was not appropriate because CO2 concentrations were lower than expected, while CH4 concentrations were greater than expected. Losses of CO2 in samples over 84 days may be attributed to leakage around septa caps designed to seal vials. Based on results of this study, it is recommended that GHG samples in Exetainer vials with chlorobutyl septa be stored no longer than 28 days before analysis for CO2, CH4, and N2O. All storage temperatures evaluated in this study were appropriate, but a temperature-controlled environment with minimal light is ideal.
Technical Abstract: Measurement of greenhouse gas (GHG) flux using static chamber methods typically occurs immediately following sample collection. However, situations may arise requiring sample storage prior to analysis by gas chromatography. Few studies have examined impacts of storage time and temperature on GHG samples retained in traditional septa-capped vials. The objective of this study was to determine effects of storage time and temperature on carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) concentrations in vials containing “low” and “high” concentrations of certified standards. Samples were stored for 3, 7, 14, 28, and 84 days at four storage temperatures: room temperature, 25°C, 4°C, and -10°C. Results indicated low and high concentration standards were not impacted by sample storage up to 28 days at any storage temperature. After 84 days, CO2 concentrations were 0.6 to 14.4% lower than expected while CH4 concentrations were up to 22% higher than expected. Results from future studies will allow for further refinement of scientifically supported guidance regarding appropriate storage temperature and time of GHG samples in septa-capped vials. Based on this study, GHG samples can be stored for up to 28 days at temperatures ranging from -10°C to 25°C.