Topographic maps of the standards mixture (a) and an EVOO sample (b) showing the volatile compounds identified by HS-GC coupled with ion mobility spectrometry (IMS): (M1m) 2-butanone monomer, (M1d) 2-butanone dimer, (M2m) 2-pentanone monomer, (M2d) 2-pentanone dimer, (M3m) 2-hexanone monomer, (M3d) 2-hexanone dimer, (M4m) 2-methyl-1-butanol monomer, (M4d) 2-methyl-1-butanol dimer, (M5m) 1-pentanol monomer, (M5d) 1-pentanol dimer, (M6m) hexanal monomer, (M6d) hexanal dimer, (M7m) trans-2-pentenal monomer, (M7d) trans-2-pentenal dimer, (M8m) ethyl acetate monomer, (M8d) ethyl acetate dimer, (M9m) ethyl butyrate monomer, (M10m) trans-2-hexen-1-al monomer, (M10d) trans-2-hexen-1-al dimer, (M11m) 1-penten-3-one monomer, M11d) 1-penten-3-one dimer, (M12m) 2-heptanone monomer, (M12d) 2-heptanone dimer, (M13m) 2-octanone monomer, (M13d) 2-octanone dimer, (M14m) 1-octen-3-one monomer, (M14d) 1-octen-3-one dimer, (M15m) ethyl isovalerate monomer, (M15d) ethyl isovalerate dimer, (M16m) propyl butyrate monomer, (M16d) propyl butyrate dimer, (M17m) trans-2-heptenal monomer, (M17d) trans-2-heptenal dimer, (M18m) heptanal monomer, (M18d) heptanal dimer, (M19m) nonanal monomer, (M20m) limonene monomer, (M20d) limonene dimer, (M21m) trans-2-octenal monomer, (M21d) trans-2-octenal dimer, (M22m) 4-methyl-pentan-2-one monomer, (M22d) 4-methyl-pentan-2-one dimer, (M23m) 6-methyl-5-hepten-2-one monomer, (M24m) hexyl acetate monomer, (M24d) hexyl acetate dimer, (M25m) 3-hexenyl acetate, (M25d) 3-hexenyl acetate.