Speciation of nitrogen bearing species using negative and
positive secondary ion spectra with Nano Secondary Ion
Mass Spectrometry
Kexue Li, § Baerbel Sinha, §, #,Peter Hoppe, §
§
Particle Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
#
Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali,
Sector 81 SAS Nagar, Manauli P.O. 140306, India
ABSTRACT: In this study we demonstrate that Nano Secondary Ion Mass Spectrometry (NanoSIMS) can be used to differentiate different nitrogen containing species commonly observed in atmospheric aerosol particles with micrometer or
sub-micrometer spatial resolution, on the basis of the relative intensity of secondary ion signals, both in negative and
positive secondary ion mode, without the need to chemically or physically separate the samples. Compounds tested include nitrate, nitrite, ammonium salts, urea, amino acids, sugars, organic acids, amides, triazine, imidazole, protein and
biological tissue. We show that NO2- secondary ions are unique to the decomposition of nitrate and nitrite salts, while
NH4+ secondary ions are unique to samples containing ammonium ions, with low signal intensities observed from amino
groups, but none from biological tissue. CN- signals are obtained from all nitrogen bearing compounds but relative signal
intensities are the highest for organic nitrogen containing compounds. We demonstrate, that quantitative determination
of the elemental fractions of carbon, oxygen and nitrate in nanometre sized aerosol samples using normalized secondary
ion intensities is possible. We further demonstrate that stable isotope ratios measured on in-house standards of unknown
isotopic composition using the 12C15N- / 12C14N- - ratio (all nitrogen containing species), the 15N16O2- / 14N16O2- - ratio (nitrate
and nitrite species) and the 15NH4+ / 14NH4+ - ratio (ammonium salts, amino acids and urea) are stable and sufficiently
precise for nitrogen isotope analysis.
Table of contents for supplementary material:
Table S1. Inorganic and organic standards used in this study.
Pages S2-S3
Table S2. Concentrations of solutions used to make aerosol-like mixture samples
Page S3-S4
14 16
14
+
Figure S3: Signal intensity of N O2 and NH4 molecular ions in different samples
Page S4
Figure S4: NanoSIMS images of the same area in negative (top) and positive (bottom) secondary ion modes. The corresponding SEM image is shown in the lower right. Primary biological particles – fungal hyphen aerosol was
collected on silicon wafer. Field of view is 30 × 30 μm2.
Page S4
Figure S5: Ambient aerosol samples from the Amazon rain forest. Green rectangular box: potassium sulfate + SOA +
POA, yellow rectangular box: soot + salt coating and blue rectangular box: ammonium sulfate + SOA. Page S5
S1
Table S3. Inorganic and organic standards used in this study.
Standard
Molecular formu- Structure
la
aerosol
N[NO3]/C = 0.1
NaNO3 + C6H12O6
N[NO3]/C = 0.5
solid
XC
XO
XN
XNO3
XS

0.40
0.52
0.04
0.56
NaNO3 + C6H12O6

0.22
0.56
0.11
0.67
N[NO3]/C = 1
NaNO3 + C6H12O6

0.14
0.57
0.14
0.71
N[NO3]/C = 2
NaNO3 + C6H12O6

0.08
0.58
0.17
0.75
N[NO3]/C = 5
NaNO3 + C6H12O6

0.04
0.59
0.19
0.78
N[NO3]/C = 0.1
KNO3 + C6H12O6

0.40
0.52
0.04
0.56
N[NO3]/C = 0.5
KNO3 + C6H12O6

0.22
0.56
0.11
0.67
N[NO3]/C = 1
KNO3 + C6H12O6

0.14
0.57
0.14
0.71
N[NO3]/C = 2
KNO3 + C6H12O6

0.08
0.58
0.17
0.75
N[NO3]/C = 5
KNO3 + C6H12O6

0.04
0.59
0.19
0.78
KNO3


0.00
0.60
0.20
0.80
NaNO3


0.00
0.60
0.20
0.80

0.00
0.50
0.25
0.00
0.57
0.29
0.14
0.00
0.67
0.00
0.17
XCl
Mixtures
Nitrate
Potassium nitrate
Sodium nitrate
Nitrite
Sodium nitrite
NaNO2
Sulfate
Ammonium sulfate
(NH4)2SO4
Barium sulfate
BaSO4


Ammino acids
Alanine
C3H7NO2

0.50
0.33
0.17
Serine
C3H7NO3

0.43
0.43
0.14
Aspartic acid
C4H7NO4

0.44
0.44
0.11
cystein
C3H7NO2S
0.43
0.29
0.14
0.07
0.63
0.23
0.16
0.01
0.46
0.54
0.00
0.60
0.40
0.00

Protein

BSA
Organic acids
citric acid
C6H8O7

Adipic acid
C6H10O4


Sugars
S2
Glucose
C6H12O6

Glucosamine HCl
C6H13NO5 +HCl
Ammonium oxalate
(NH4)2C2O4
Urea
CO(NH2)2
N-1 adamantyl urea

0.50
0.50
0.00

0.46
0.38
0.08

0.25
0.50
0.25

0.25
0.25
0.50
C11H18N2O

0.79
0.07
0.14
Tri(2-pyridyl)striazine
C18H12N6

0.75
0.00
0.25
1,8 naphtalimide
C12H7NO2

0.80
0.13
0.07
Dicyandiamide
NH2C(=NH)NHCN

0.33
0.00
0.67
Benzylimidazole
C10H10N2

0.83
0.00
0.17
polycarbonate
[C16H14O3]n

0.84
0.16
0.00
0.08
Others
Table S4. Concentrations of solutions used to make aerosol-like mixture samples.
Standard
Sodium nitrate (NaNO3)
2-Deoxy-D-glucose (C6H12O6)
Molar mass
85.00
180.16
N or C atom number
1
6
Samples
N/C
NaNO3 (g/L)
2-Deoxy-D-glucose
(C6H12O6) (g/L)
NaNO3-C-1
0.1
4.41
15.59
NaNO3-C-2
0.5
11.72
8.28
NaNO3-C-3
1
14.78
5.22
NaNO3-C-4
2
17.00
3.00
S3
NaNO3-C-5
5
18.68
1.32
Standards
Potassium nitrate (KNO3)
2-Deoxy-D-glucose (C6H12O6)
Molar mass
101.00
180.16
Samples
N/C
KNO3 (g/L)
2-Deoxy-D-glucose
(C6H12O6) (g/L)
KNO3-C-1
0.1
5.03
14.97
KNO3-C-2
0.5
12.54
7.46
KNO3-C-3
1
15.42
4.58
KNO3-C-4
2
17.41
2.59
KNO3-C-5
5
18.88
1.12
14
16
-
14
+
Figure S3: Signal intensity of N O2 and NH4 molecular ions in different samples
S4
Figure S4: NanoSIMS images of the same area in negative (top) and positive (bottom) secondary ion modes. The corresponding SEM image is shown in the lower right. Primary biological particles – fungal hyphen aerosol was collected on sili2
con wafer. Field of view is 30 × 30 μm .
Figure S5: Ambient aerosol samples from the Amazon rain forest. Green rectangular box: potassium sulfate + SOA + POA,
yellow rectangular box: soot + salt coating and blue rectangular box: ammonium sulfate + SOA.
S5