Supplement of Atmos. Meas. Tech., 9, 2909–2925, 2016
http://www.atmos-meas-tech.net/9/2909/2016/
doi:10.5194/amt-9-2909-2016-supplement
© Author(s) 2016. CC Attribution 3.0 License.
Supplement of
Evaluation of NO+ reagent ion chemistry for online measurements of
atmospheric volatile organic compounds
Abigail R. Koss et al.
Correspondence to: Abigail R. Koss ([email protected])
The copyright of individual parts of the supplement might differ from the CC-BY 3.0 licence.
Figure S1. Ion source and drift tube schematic.
Figure S2. Ion guide voltage settings. The top panel shows the absolute voltage setting (from
ground); the middle panel highlights the changes in voltage potential between H3O+ and NO+
settings, and the bottom panel is a cartoon of the ion guide section taken from the CI-API manual
(Aerodyne Inc./Tofwerk AG). The horizontal (axial) distances are not to scale.
Figure S3. Comparison of product ion distributions between NO+ CIMS and H3O+ CIMS. The
complete product ion distribution of n-propylbenzene is shown as an example of a compound
with a complex mass spectrum resulting from H3O+ chemistry, and a simple mass spectrum
resulting from NO+ chemistry.
Figure S4. Product ion distributions of selected aliphatic hydrocarbons, at a relative humidity of
20%.
Figure S5. Example chromatograms and relative sensitivity calculation of ethanol for Table 2.
Figure S6. Humidity dependence of primary ions and VOCs. (a) Impurity ions and water
clusters. (b) Carbonyls. (c) Aromatics. (d) Acetonitrile. Acetonitrile is detected with poor
sensitivity using NO+; the NO+ and H3O+ products are approximately equal in magnitude.
Figure S7. Speciated contributions to various NO+ CIMS masses, in urban air. Values on Y-axes
are the fractional contribution of each VOC to total signal. Includes m/z 41-m/z 78.
Figure S8. Figure S7, continued. Includes m/z 82-m/z 111.
Figure S9. Figure S7, continued. Includes m/z 113-m/z 144.
Figure S10. A. Background and ambient measurements taken during urban air sampling with the
NO+ ToF-CIMS. B. Example multiple-point calibrations of the NO+ ToF-CIMS showing
sensitivity linear with concentration.
Figure S11. Example isobaric interferences for heptanone measured with H3O+ CIMS, at m/z
115 C7H14OH+, and with NO+ CIMS, at m/z 144 C7H14ONO+. Although the resolution m/dm is
better at m/z 144, there are more possible isobaric interferences and the average distance to
neighboring peaks is smaller. The m/z range of each window is 10 FWHM. H3O+ ToF-CIMS
mass spectrum courtesy of M. Coggon, collected in Boulder, CO in Dec. 2015.
Table S1. VOCs sampled in series GC-ToFCIMS laboratory experiments.
β-pinene
VOC name
Formula
limonene
alkanes
ethane
propane
n-butane
n-pentane
n-hexane
n-octane
n-decane
n-undecane
i-butane (2-methylpropane)
i-pentane (2-methylbutane)
2,2-dimethylbutane
2-methylpentane
2,3-dimethylbutane
3-methylpentane
2,4-dimethylpentane
2-methylhexane
2,3-dimethylpentane
3,3-dimethylpentane
3-methylhexane
2,2,4-trimethylpentane
2,3,4-trimethylpentane
2-methylheptane
3-methylheptane
4-methylheptane
C2H6
C3H8
C4H10
C5H12
C6H14
C8H18
C10H22
C12H26
C4H10
C5H12
C6H14
C6H14
C6H14
C6H14
C7H16
C7H16
C7H16
C7H16
C7H16
C8H18
C8H18
C8H18
C8H18
C8H18
alkenes
ethene
propene
ethyne
trans-2-butene
1-butene
iso-butene (2-methylpropene)
cis-2-butene
1-pentene
trans-2-pentene
cis-2-pentene
1-hexene
isoprene
C2H4
C3H6
C2H2
C4H8
C4H8
C4H8
C4H8
C5H10
C5H10
C5H10
C6H12
C5H8
cycloalkanes
cyclopentane
methylcyclopentane
cyclohexane
methylcyclohexane
ethylcyclohexane
1,1-dimethylcyclopentane
ethylcyclopentane
C5H10
C6H12
C6H12
C7H14
C8H16
C7H14
C7H14
monoterpenes
α-pinene
C10H16
camphene
γ-terpinene
α-phellandrene
1,8-cineol
3-carene + myrcene
C10H16
C10H16
C10H16
C10H16
C10H16
C10H16
C10H16
aromatics
benzene
toluene
ethylbenzene
m-xylene + p-xylene
o-xylene
vinylbenzene (styrene)
isopropylbenzene
n-propylbenzene
1-ethyl,3-methylbenzene + 1ethyl,4-methylbenzene
1,3,5-trimethylbenzene
1-ethyl,2-methylbenzene
1,2,4-trimethylbenzene
1,2,3-trimethylbenzene
1,3-diethylbenzene
1,4-diethylbenzene
C6H6
C7H8
C8H10
C8H10
C8H10
C8H8
C9H12
C9H12
C9H12
C9H12
C9H12
C9H12
C9H12
C10H14
C10H14
aldehydes
acetaldehyde
propanal
butanal
pentanal
hexanal
heptanal
octanal
methacrolein
C2H4O
C3H6O
C4H8O
C5H10O
C6H12O
C7H14O
C8H16O
C4H6O
ketones
acetone
2-butanone (MEK)
3-methyl-2-butanone
2-pentanone
3-pentanone
3-hexanone
methyl vinyl ketone (MVK)
C3H6O
C4H8O
C5H10O
C5H10O
C5H10O
C6H12O
C4H6O
other
methanol
ethanol
2-propanol
methyl-t-butyl ether (MTBE)
acetonitrile
3-methyfuran
CH4O
C2H6O
C3H8O
C5H12O
C2H3N
C5H6O