Carbopack b

In general, GC–IMS cannot identify unknown substances, but the combination of GC retention time and ion mobility renders identification possible via a comparison to an in‐house substance database. This database was generated by the analysis of pure reference compounds (purchased from Merck, Darmstadt, Germany, and Carl Roth, Karlsruhe, Germany) and by comparison of the Kovats retention indices (RI) to a series of n‐ketones, combined with complementary GC–MS (Appendix S3). The sampling for the GC–MS measurements was conducted using adsorption needles (NeedleTraps; PAS Technology, Magdala, Germany), which were filled with a combination of three different sorbents (Carbopack B, 1 cm; Carboxen 1016, 1 cm; and Carboxen 1000, 1 cm; Sigma‐Aldrich, St. Louis, Missouri, USA) to ensure the adsorption of the entire expected range of pVOCs.
Reference compounds of common floral volatiles in the genus Narcissus were selected based on data from the literature (Dobson et al., 1997 (link); Marques et al., 2016 (link)) and the complementary GC–MS measurements.

All the tested LAB strains from A. mellifera were incubated anaerobically for 7 days in Pollen media (50 ml). Bacterial cultivations were performed separately in one anaerobic jar for each strain. The diffusive sampler was attached onto the inner side of the jar's lid. A diffusive sampler having uptake rates that fully agree with the theories behind diffusive sampling was used for sampling and analysis of formic and acetic acids (Ferm 2001, www.diffusivesampling.ivl.se). Analysis was made using ion chromatography with a gradient eluent generator (DIONEX ICS 2000). Diffusive sampling of other organic vapours was made with tube‐typed sorbent tubes (PerkinElmer, Waltham, MA). For sampling of benzene, toluene, n‐octane, ethylbenzene, m‐, p‐xylene, o‐xylene and n‐nonane, Carbopack B (Sigma‐Aldrich) was used as an adsorbent. The pollutants were analysed via thermal desorption (ATD‐400, PerkinElmer) and gas chromatography with a flame ionisation detector (GC‐FID, Varian3800). More samplers could be analysed when Tenax TA was used as sorbent, and analysis was made with thermal desorption (Markes, Frankfurt, Germany) and GC–MS (Agilent Technologies). Experimentally determined uptake rates were used for the thermally desorbed hydrocarbons.