Supplement of Atmos. Meas. Tech., 9, 5315–5329, 2016
http://www.atmos-meas-tech.net/9/5315/2016/
doi:10.5194/amt-9-5315-2016-supplement
© Author(s) 2016. CC Attribution 3.0 License.
Supplement of
Sensitive detection of n-alkanes using a mixed ionization mode protontransfer-reaction mass spectrometer
Omar Amador-Muñoz et al.
Correspondence to: Omar Amador-Muñoz ([email protected])
The copyright of individual parts of the supplement might differ from the CC-BY 3.0 licence.
Example application of the calibrated fragment algorithm for quantifying n-alkanes mixtures
The algorithm explained in section 2.3 was applied to calculate n-decane (m/z 142) concentration, taken as an
example, in a mixture created in the laboratory containing nine n-alkanes:
1. wcps(O2+) for n-decane = 77256 at 541.5 ppbv.
2. wS(O2+) = 142.7 wcps/ppbv
3. FCD of m/z 142 on: m/z 156 (n-undecane) = 0.005, m/z 170 (n-dodecane) = 0.053 and m/z 184 (ntridecane) = 0.059 (Table 3).
4. Over signal of m/z 142 ion: [11621 wcps * 0.005 (n-undecane)] + [17717 wcps * 0.053 (n-dodecane)]
+ [18887 wcps * 0.059 (n-tridecane)] = 2111 wcps.
5. Pure signal of m/z 142 ion: 10099 wcps - 2111 wcps = 7988 wcps.
6. 𝑛 − decane concentration =
7992 𝑤𝑐𝑝𝑠
142.7
𝑤𝑐𝑝𝑠
ppbv
= 57.0 𝑝𝑝𝑏𝑣
7. The bias with respect to the known concentration of n-decane (60.0 ppbv, Table S2) was -5.0 % as
illustrated in table 4.
Figures
The panels in figure S1 show the variability at low water flow (2 sccm) of the key source ions comprising H3O+
(m/z 19), O2+ (m/z 32), NO+ (m/z 30) and H2O.(H3O)+ (m/z 37) as a function of E/N. Due to excessive water
clusters at low E/N found at 6 sccm (HWF), the primary ion (H3O+) was saturated. The intensity of H2O.(H3O)+
decreased, when E/N increased because a de-clustering effect occurs at higher electric fields (Blake et al. 2009).
Higher intensities were observed at low water flow for all n-alkanes. Sensitivities increased when O2+ increased.
a
m/z 127
m/z 128
m/z 129
m/z19
m/z 30
m/z32
m/z 37
20
2,5
18
2,0
14
12
1,5
10
8
1,0
6
4
0,5
2
180
150
120
90
60
180
150
120
90
60
180
150
120
90
60
180
150
120
90
60
180
150
90
120
0,0
60
0
83 83 83 83 83 91 91 91 91 91 101 101 101 101 101 109 109 109 109 109 122 122 122 122 122
E/N (Td), USO (V)
cps/ppbv
Count rate (cps x 106)
16
b
m/z 155
m/z 156
m/z 157
m/z19
m/z 30
m/z32
m/z 37
20
6
18
5
14
4
12
10
cps/ppbv
Count rate (cps x 106)
16
3
8
2
6
4
1
2
180
150
120
90
60
180
150
120
90
60
180
150
120
90
60
180
150
90
120
60
180
150
90
120
0
60
0
83 83 83 83 83 91 91 91 91 91 101 101 101 101 101 109 109 109 109 109 122 122 122 122 122
E/N (Td), USO (V)
c
m/z 170
m/z 171
m/z19
m/z 30
m/z32
m/z 37
180
150
120
90
0
60
0
180
1
150
2
120
2
90
4
60
3
180
6
150
4
120
8
90
5
60
10
180
6
150
12
120
7
90
14
60
8
180
16
150
9
120
18
90
10
60
20
83 83 83 83 83 91 91 91 91 91 101 101 101 101 101 109 109 109 109 109 122 122 122 122 122
E/N (Td), USO (V)
Figure S1. Intensity of signals (counts per second, cps) for H3O+ (m/z 19), NO+ (m/z 30), O2+ (m/z 32),
H2O.(H3O)+ (m/z 37) and sensitivities (cps/ppbv) for n-alkanes at low water flow (2 sccm). a. nnonane, b. n-undecane and c. n-dodecane. Data are shown for tests at five E/N ratios (83, 91, 101,
109 and 122 Td) and five U SO voltages (60, 90, 120, 150 and 180).
cps/ppbv
Count rate (cps x 106)
m/z 169
a
1200
120
E/N ratio, Td
110
1000
100
m/z 128, cps
800
90
600
400
200
0
2
4
6
8
10
12
6
14
16x10
m/z 32 cps
b
2000
120
m/z 156, cps
100
E/N ratio, Td
110
1500
90
1000
500
0
2
4
6
8
10
12
6
14
16x10
m/z 32 cps
c
3500
120
m/z 170, cps
110
2500
100
2000
90
E/N ratio, Td
3000
1500
1000
500
0
2
4
6
8
10
12
14
6
16x10
m/z 32 cps
Figure S2. Intensities of m/z 32 (O2+) vs. intensities of charge transfer products for (a) n-nonane (m/z 128), (b)
n-undecane (m/z 156) and (c) n-dodecane (m/z 170). Marker size illustrates the U SO: Smallest 60 V and largest
180 V.
Figure S3. Mass spectra of n-decane. WF2, USO 60 V. E/N ratios from 83 to 122 Td.
M-H
M
100
90
80
% difference
70
60
50
40
30
20
10
0
cps/ppbv
ncps/ppbv, O2+
ncps/ppbv, NO+
ncps/ppbv, O2+,NO+
Sensitivities under different mechanisms
Figure S4. Difference of absolute sensitivities (cps/ppbv) and normalized sensitivities (ncps/ppbv) between two
sets of experiments in percentage. Average and standard deviation (bars) shown including data for n-nonane,
n-decane, n-undecane and n-dodecane. The dominant mechanism for these n-alkanes was CT.
a
80
120
110
m/z 140, cps
60
100
50
E/N ratio, Td
70
90
40
30
20
10
0
4
6
8
10
12
14
6
16
18x10
m/z 32 cps
b
3000
120
110
100
m/z 84, cps
2000
E/N ratio, Td
2500
90
1500
1000
500
0
4
6
8
10
12
14
16
18
6
20x10
m/z 32 cps
Figure S5. Intensities of double hydride abstraction for (a) n-decane (m/z 140) and (b) n-hexane (m/z 84) vs.
O2+ (m/z 32). Marker size illustrates the U SO: Smallest 60 V and largest 180 V.
A chromatogram of fresh liquid oil MC252 analyzed by Two-Dimensional Gas Chromatography with HighResolution Time-of-Flight Mass Spectrometry using Vacuum UV Ionization (GCxGC/VUV-HRTOFMS) is
shown in Figure S6. Oil MC252 was obtained from the Macondo well located in Mississippi Canyon lease
block 252 in the Gulf of Mexico on May 20th 2010. Oil samples were diluted (500:1) in n-hexane. 1 µL of
diluted oil was injected in splitless at 320 ºC. Analytes were transferred to the gas chromatograph (GC, Agilent
7890). Hydrocarbons were separated on a non-polar primary column (60 m × 0.25 mm × 250 μm Rxi-5Sil-MS;
Restek) connected to a second-dimension polar column (1 m × 0.25 mm × 0.25 μm, Rtx-200MS, Restek Corp.)
by a dual loop modulator (1.5m × 0.25 mm Rxi guard column) cooled with air from a cold finger and
periodically heated by a pulse of hot air (Zoex Corp.). Helium was used as carrier gas at a flow rate of 2 mL
min-1. The GC temperature program was 40 °C hold for 2 min, 3.5 °C min -1 until 320 °C and hold for 10 min.
Ionization conditions of the analytes are described in detail by Worton et al. (2015). Briefly, analytes were
ionized with 10.5 electron volts (eV) vacuum ultraviolet photoionization (VUV) in a time of flight mass
spectrometer (HTOF, Tofwerk). The VUV beam was generated by the Chemical Dynamics Beamline 9.0.2 of
the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory. VUV ionization affords much
less fragmentation than conventional electronic ionization (70 eV), increasing the molecular ion intensity.
Quantification of n-alkanes was made using deuterated n-dodecane (n-C12D26) at 4.9 ng µL-1 internal standard
and relative response factor.
Figure S6. Two-Dimensional Chromatogram of fresh oil MC252.
Tables
Table S1. Straight chain alkanes. Concentrations to evaluate sensitivities.
#
Compound
Concentration, ppbva
1 level
2nd level
931.9
2290.7
812.4
1997.0
724.1
1179.9
644.2
1583.5
586.0
1440.4
541.5
1331.1
496.2
1219.8
458.3
1126.5
426.8
1049.2
st
1
2
3
4
5
6
7
8
9
a
n-Pentane
n-Hexane
n-Heptane
n-Octane
n-Nonane
n-Decane
n-Undecane
n-Dodecane
n-Tridecane
3st level
3648.9
3181.1
2835.3
2522.4
2294.5
2120.3
1943.1
1794.5
1671.3
Concentrations were calculated at 1 atm, T= 18-23 °C, R = 0.08205746 L atm/K mol.
Table S2. Straight chain alkanes. Concentrations to evaluate the algorithm.
#
Compound
Concentration, ppbva
1 level
2nd level
106.3
247.8
89.0
218.7
79.3
194.9
71.5
175.7
65.0
159.8
60.0
147.5
55.0
135.2
51.1
125.6
47.6
116.9
st
1
2
3
4
5
6
7
8
9
a
n-Pentane
n-Hexane
n-Heptane
n-Octane
n-Nonane
n-Decane
n-Undecane
n-Dodecane
n-Tridecane
3st level
394.7
277.6
247.4
223.1
202.9
187.2
171.6
159.4
148.4
Concentrations were calculated at 1 atm, T= 18-23 °C, R = 0.08205746 L atm/K mol.
References
Blake, R. S.; Monks, P. S. and Ellis, A. M.: Proton-Transfer Reaction Mass Spectrometry, Chem. Rev., 109,
861-896, doi: 10.1021/cr800364q, 2009.
Worton, D. R.; Zhang, H.; Isaacman-VanWertz, G.; Chan, A. W. H.; Wilson, K. R. and Goldstein, A. H.:
Comprehensive Chemical Characterization of Hydrocarbons in NIST Standard Reference Material 2779 Gulf
of Mexico Crude Oil, Environ. Sci. Technol., 49(22), 13130-13138, doi:10.1021/acs.est.5b03472, 2015.