Table S1. Recovery rates from single STs exposed for 3 h to 2 µL of a standard solution in
30, 300, or 600 mL glass screw-cap bottles. STs were analyzed by TD-GC-QMS immediately
after exposure. Recovery rate in % was calculated as (signal in sample)/(mean signal in 5
injections of standard)x100 after a dilution series of the standard had been run to ensure
accurate quantification (n = 5, mean ± SD).
Table S2. Efficiency of thermal desorption of PVs from STs. One µL of a 50 ng solution of
the standard mix in Figure 1 was either added directly to STs (direct addition, n = 5), or
injected into the headspace around an ST in a 1.5 mL clear screw-cap GC vial and incubated
for 3 h (headspace addition, n = 5), and each ST was desorbed once (1st desorption) and then
desorbed again (2nd desorption) with the TDU program described in Methods S1. Recovery in
% (mean ± SD) was calculated by comparison to the mean signal (n = 5) from 1 µL of the
same 50 ng standard injected by a liquid autosampler onto the same instrument, analyzed with
the same GC-MS method (see Methods S1); both TDU and liquid injection programs were
run with a 1 to 20 split ratio as described in Methods S1.
Table S3. Relative amounts of PVs (mean ± SD, n = 8) detected over a time course after
W+OS treatment, collected every 4 h on STs (dark columns) or Poropak Q filters (light
columns), corresponding to Figure 4; nd, not detected.
Figure S1. Recovery from STs by length. We analyzed the recovery of volatiles collected
from either standards or plant samples on STs of different lengths (0.25, 0.5, 0.75, 1.0, 1.25
and 1.5 cm corresponding to 4.4, 8.8, 13, 18, 22, and 26 μL volume, respectively).
(a,b) For the measurement of standards, 2 µL of dichloromethane containing 100 ng of either
α-pinene or β-caryophyllene were injected into 4 mL glass vials, each containing an ST. After
3 h, STs were individually collected and analyzed (mean + SD, n = 5).
(c, d) For plant samples, one rosette leaf per plant on N. attenuata plants was wounded and
immediately placed in ventilated PET cups (Methods S1) each containing one ST of each
different length. After 1 h, STs were collected and analyzed. As representative values, we
determined the peak areas of 2(E)-hexen-1-al and 3(Z)-hexen-1-ol (mean + SD, n = 8).
Figure S2. Chromatogram overlay of a freshly prepared ST or an ST stored under Ar. STs
were prepared as described and analyzed by GC-TD-MS either immediately after
conditioning, or after 2 months of storage under Ar. All peaks visible in the total ion
chromatogram (TIC) can be found in different intensities in both samples and are from
silicone or a few known contaminants in the STs which can be easily separated from PVs, and
are not removed by cleaning.
Figure S3. Recovery rates from STs stored in vials of different volumes up to 10 days at
room temperature (RT). We injected 2 µL of dichloromethane containing 240-400 ng of the
least stable or most volatile, and thus most easily lost, components of our standard mix: (a)
2(E)-hexen-1-al (400 ng), (b) 3(Z)-hexen-1-ol (240 ng), (c) 3(Z)-hexen-1-ol-acetate (250 ng),
and (d) α-pinene (310 ng), into 4 mL glass vials each containing 5 STs. After 3 h, the 5 STs
from each 4 mL vial were individually collected and stored in new vials for 1, 3, 5, and 10
days at RT. All five STs from each 4 mL exposure vial were placed in the same type of
screw-cap storage vial: either 250 µL clear glass, 1.5 mL clear glass, 1.5 mL amber glass
under Ar sealed with Teflon tape, 4 mL clear glass, or 20 mL clear glass. Because 2 µL of
standard was distributed among five STs, recovery rate in % was calculated as (signal in
sample)/(mean signal in 5 injections of 2:5 diluted standard)x100 (mean + SD, n = 5, a:
amber vials).
Figure S4. Standard curves of representative PVs collected on STs. To determine the linear
range of the ST GC-TD-MS method, we chose standard compounds to represent different
groups of PVs: green leaf aldehydes (a, 2(E)-hexen-1-al), alcohols (b, 3(Z)-hexen-1-ol) and
their esters (c, 3(Z)-hexenyl acetate), monoterpenes (d, α-pinene; e, Z and E ocimene) and
their alcohols (f, linalool), and sesquiterpenes (g, (E)-β-farnesene; h, β-caryophyllene). All
standards were mixed in concentrations ranging from 0.1 to 10 ng per µL dichloromethane,
and 1 µL was injected into a 4 mL glass vial containing one ST. After 3 h, STs were
individually collected and analyzed. Each dot represents one independent analysis with n = 5
measurements per concentration; straight lines represent linear regressions, r²: coefficient of
determination.
Figure S5. Standard curves of representative PVs analyzed by liquid injection. To compare
the linearity of the ST GC-TD-MS method with liquid injection-GC-MS analysis of the
standard solution, we analyzed the same solutions used for the determination of validation
parameters in Figure S4: (a) 2(E)-hexen-1-al, (b) 3(Z)-hexen-1-ol, (c) 3(Z)-hexenyl acetate,
(d) α-pinene, (e) Z and E ocimene, (f) linalool, (g) (E)-β-farnesene, and (h) β-caryophyllene.
One µL of each mixture was injected into the same GC-MS connected to the TD using a
liquid autosampler, and measured using the same GC-MS program. Each dot represents one
independent analysis with n = 5 measurements per concentration; straight lines represent
linear regressions, r²: coefficient of determination.
Figure S6. Reproducibility of ST sampling. Two µL of dichloromethane containing either 5
or 10 ng of either (a) α-pinene or (b) β-caryophyllene were added to 4 mL glass vials, each
containing 5 STs of 0.5 cm length. After 3 h, STs were collected and individually analyzed
(mean + SD, n = 5).
Figure S7. Exposure-time-dependent recovery of different PVs from STs. To determine
optimal exposure times for ST volatile trapping, we collected the headspace from 2 µL
dichloromethane containing 100 ng of either (a) 2(E)-hexen-1-al, (b) α-pinene, or (c) βcaryophyllene and injected into 4 mL glass vials each containing a 0.5 cm ST. After 3, 6, 9 or
12 h of exposure, STs were collected and analyzed (mean ± SD, n = 5).
Figure S8. Temperature-dependent recovery of different PVs from STs. The recovery from
STs was tested at different ambient temperatures (4, RT ≈ 20, 26, 37 and 50 °C) for 3 classes
of volatiles. Four µL dichloromethane containing 40 ng of the standard mixture in Figure 1
was added to the headspace of 20 mL glass vials each containing a 0.5 cm ST. After 3 h, STs
were collected and analyzed. Representative volatiles are shown: (a) 2(E)-hexen-1-al, (b) αpinene, or (c) β-caryophyllene (mean ± SD, n = 5).