1 ANALYSIS OF THE ORGANIC MASS SPECTRA 10 2 10 3 10 4 10 5 10 6 Ion Rate (Hz) 160 140 120 100 80 60 40 20 m/z (Daltons) Pedregal 2/15 12:50 - 15:40 run# 457-474 Air Water Nitrate Sulphate Ammonium Chloride Organics Typical Ambient Mass Spectrum INORGANICS/AIR: Air m/z´s: 14(N + ), 28(N 2 + ), 32(O 2 + ), 40 (CO + ) *** Water m/z´s: fragment of 18 (H 2 O + ) Nitrate m/z´s: 30 (NO + ), 46 (NO 2 + ) Sulphate m/z´s: 48 (SO + ), 64 (SO 2 + ), 80 (SO 3 + ), 81 (SO 3 + ) Ammonium m/z´s: fragmens of 15 (NH + ), 16 (NH 2 + ), 17 (NH 3 + ) Chloride m/z´s: fragments of 36 (H 35 Cl), 38 (H 37 Cl) ORGANICS: No separation of individual species prior to vaporization & ionization Overlapping patterns of multiple molecules.
Transcript
1
ANALYSIS OF THE
ORGANIC MASS SPECTRA
102
10 3
104
105
10 6
Ion
Rat
e (H
z)
16014012010080604020m/z (Daltons)
Pedregal2/15 12:50 - 15:40run# 457-474
Air Water Nitrate Sulphate Ammonium Chloride Organics
Typical Ambient Mass Spectrum
INORGANICS/AIR:
Air m/z´s: 14(N+), 28(N2+), 32(O2
+), 40 (CO+) ***Water m/z´s: fragment of 18 (H2O+)Nitrate m/z´s: 30 (NO+), 46 (NO2
+)Sulphate m/z´s: 48 (SO+), 64 (SO 2
+), 80 (SO 3+), 81
(SO3+)
Ammonium m/z´s: fragmens of 15 (NH+), 16 (NH2+),
17 (NH3+)
Chloride m/z´s: fragments of 36 (H35Cl), 38 (H37Cl)
ORGANICS:
No separation of individual species prior to vaporization & ionization
Overlapping patterns of multiple molecules.
2
Field Spectra:
1) Look at Correlations in Time and Size of Fragments to Identify those that may belong to same parent
2) Look at correlations in time between organic fragments and
Gas phase measurements
“Typical” aerosol mass spectra
12840
x103
250200150100500
403020100
x103
2520151050
x10
3
2520151050
x10
3
Sulfate
Hydrocarbon
Biomass Burning Marker
Fluorocarbon
44 (CO2+)
CO2+ is marker for oxygenated organic
Aerosol composition can be classified from mass spectrum
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Ion Series in Mass Spectra
• CH2 Ion Series *: “PicketFence” like spectra in whichgroups of peaks have 14 amuseparation.
• Masses at which peaksappear are characteristic ofR backbone. Series withdifferent R’s are classifiedaccording to their ∆ value∆ = Peak mass - 14n + 1
CH2
-6
-4
-2
0
4
6
∆ S
CA
LE
-6
-4
-2
0
2
4
6
-7
-6
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-4
-3
-2
-1
0
1
2
3
4
5
6ester
alkyl
aromatic
C-O2+
(ketone, alcohol,...)
C-O+
terpene 79
amine, amide 58, 86
7 6
alcohol
cycloalkane
acid
alkene
cycloalkene
cycloalkene
alkene
ROCOOR 63 77 91
77
5 0
5 1
27
diene, alkyne
5 6
386 6
cycloalkyl
alkyl
esterdiketone
C 2H3O+ 43
R
CH2
CH2
CH2
CH3
* “Interpretation of Mass Spectra” by McLafferty F.W. and Turecek , F.
Diesel Aerosol Composition
Main Chemical Compounds in Diesel and Lubricant Oil:
n-alkanes,branched alkanes, cyloalkyl species
1.0
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nsity
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Uni
ts)
160140120100806040200
m/z (amu)
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20
0 Ion
Rat
e (1
000
Hz)
16012080400
m/z (amu)
Lab Diesel Aerosol
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“Typical” aerosol mass spectra
12840
x10
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403020100
x10
3
25
Sulfate
Hydrocarbon
44 (CO2+)
CO2+ is marker for oxygenated organic
“hydrocarbon”e-
CnHm ----> Cn’Hm’+
27, 29, 41, 43, 55, 57, 69, 71, …“oxygenated”
e-CnHmOy ----> CO2
+ H3C2O + HCO2 + Cn’Hm’ +
44 43 45 55, 57, ...
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Photochemical Particles
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rela
tive
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trib
utio
n
-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Delta
Composition - Organic Particles
Application of Delta Analysis to Field Data:
( NYC Supersite- Frank Drewnick)
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Examples of Mass Spectra seen by various AMS Users…..
What we are looking for is common features among these spectra that may be useful in determining the relative importance of various organic groups in the organic Mass Spectra.
Combustion Sources
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Urban Mixes
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Photochemical Time Periods
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Rural/Biogenic/Marine Environments
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Note: even though this was supposed to be a rural site, it had quite a bit of urban influence from nearby towns
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Lab Experiments
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Acknowledgements to the AMS Users for sharing their Mass Spectra with us for this compilation!!!
