Post on 19-Jan-2016
Background
• Aerosols are studied for– Environment impact
• Direct climate effect• Indirect climate effect
– Biofuels– Human health impact
• Medicinal• Cigarette smoke
Direct effect: smog, decreased visibility
Indirect effect: acid rain, damage to historic landmarks
Introduction
• Ambient organic aerosol– Heterogeneous composition– Secondary reactions occur in particle
• Off-line filter sampling– Longer analysis times– Allows secondary reactions to occur to a greater
extent
• Mass spectrometry– Real-time analysis– Structural information– Range of compounds
Mass Spectrometry for Aerosol Analysis
• Real time analysis–Ambient sampling–MSn capabilities–Transportability
• Quadrupole ion trap–Compact–High sensitivity–High MS/MS efficiency
Py-LTPI Ionization Method
Experimental
• Bruker Esquire 3000 • 50 mg sample pyrolyzed • 5 minute equilibration prior to
analysis• ~2 minutes to reach maximum
temperature• Spectra averaged over the course of
pyrolysis
Cellulose and Lignin
• Natural polymers • Primary
components of cell wall
• Contain mostly carbon, hydrogen, and oxygen
Cellulose
Lignin
Py-LTPI of Cellulose
97
111
127
137
143
149 163 177191
205 219229 243 257 279
0.0
0.5
1.0
1.5
2.0
Inte
nsity
x 1
05
100 120 140 160 180 200 220 240 260 280 m/z
Mass-to-charge ratios can be compared to previously identified compounds
Positive Ion Detection Mode
Negative Ion Detection Mode
113.3 127 141 157171
185 205
227241
255
269
277
283
0
500
1000
1500
2000
Inte
nsity
100 120 140 160 180 200 220 240 260 280 m/z
Previously Identified Compounds in Cellulose
O
OHOO O
O
OOH
O
OH O
O
3,5-dihydroxy-2-methyl-4H-pyran-4-one142 Da
5-hydroxymethyl-furfural126 Da
Furfural96 Da
Levoglucosenone126 Da
Levoglucosan162 Da
2-methyl-3-hydroxy-4-pyrone126 Da
O
O
Syringaldehyde182 Da
4-ethylsringol182 Da
2,6-dimethoxyphenol154 Da
O O
OH
O
O O
OH
O O
OH
O
OH
HOHO
O
Some previously identified compounds have the same mass and will have the same mass-to-charge ratios.
Tandem Mass Spectrometry (MS/MS)
• Used to differentiate between ions of the same mass-to-charge ratio
• Ions are subjected to collision-induced dissociation (CID)–Ions dissociate into product ions–Ions can be differentiated by
dissociation patterns
63 71 109 114
127
0
250
500
750
1000
1250
Inte
nsity
60 70 80 90 100 110 120 m/z
3-Hydroxy-2-Methyl-4-Pyrone Standard
69
71 81 8385
97
99109
127
0
1000
2000
3000
Inte
nsity
60 70 80 90 100 110 120 m/z
Cellulose Aerosol Product
MS/MS of 127 Da
Only two common fragment ions and the relative intensities for 127 and 109 are dissimilar. Unlikely a compound in cellulose aerosol.
95
123
140 155
0
2
4
6
8
Inte
nsity
x 1
05
80 90 100 110 120 130 140 150 m/z
81 8395 99
109
111
123
127
137140 155
0.00
0.25
0.50
0.75
1.00
1.25
Inte
nsity
x 1
04
80 90 100 110 120 130 140 150 m/z
2,6-Dimethoxyphenol Standard
Cellulose Aerosol Product
MS/MS of 155 Da
All fragment ions of 2,6-Dimethoxyphenol match fragment ions of cellulose aerosol. 2,6-Dimethoxyphenol could be a compound in cellulose aerosol.
Cellulose Summary
• MS/MS by CID allows for comparison of cellulose aerosol product to standards
• Some peaks match those of standards and could be found in aerosol product
• Some peaks do not match previously identified compounds
Py-LTPI of Lignin
110124 138
151
165179 191 207 227 241249
255
269279
0
2
4
6
Inte
nsity
x 1
04
100 120 140 160 180 200 220 240 260 280 m/z
Positive Ion Detection Mode
Negative Ion Detection Mode
112 124 141
149.
154167
182 196 210219 233
247
257
271
279
287.
0
2000
4000
6000
8000
Inte
nsity
100 120 140 160 180 200 220 240 260 280 m/z
Can the same previously identified compounds from be found in lignin?
95
123
140 155
0
2
4
6
8
Inte
nsity
x 1
05
80 90 100 110 120 130 140 150 m/z
2,6-Dimethoxyphenol Standard
Lignin Aerosol Product
MS/MS of 155 Da
86
99109 113 123
127
137 140
152
0
200
400
600
800
1000
Inte
nsi
ty
80 90 100 110 120 130 140 150 m/z
Not all of the fragment ions of standard match the aerosol product and the relative intensities of fragment ion 127 are dissimilar. Unlikely a compound in lignin aerosol.
MS/MS of 127 Da
63 71 109 114
127
0
250
500
750
1000
1250
Inte
nsity
60 70 80 90 100 110 120 m/z
3-Hydroxy-2-Methyl-4-Pyrone Standard
Lignin Aerosol Product
69
81 8385
97
99
109
127
0
100
200
300
400
500
Inte
nsity
60 70 80 90 100 110 120 m/z
71
At the same CID voltage, the standard and aerosol product yield different relative intensities for ions 127 and 109. Unlikely a compound in pyrolyzed lignin aerosol.
Unexpected Losses
83
97 111121
129
139.
147
157
175
0
50
100
150
Inte
nsity
80 90 100 110 120 130 140 150 160 170 m/z
75 87
97
111
125141
143
159
169
187
0
10
20
30
40
Inte
nsity
80 100 120 140 160 180 m/z
172
Parent ion: 157; Net loss of 10; possible loss of 28 and gain of 18
Loss of 15; possible loss of a methyl radical
Conclusions• Some previously identified standards
match well with the cellulose aerosol product
• The same standards do not match well with ions in lignin aerosol product
• Unexpected losses of 15 Da and
10 Da
Future Work
• Further investigation of cellulose and lignin aerosol products– Comparison of previous identified compounds
in negative mode– Comparison of other cellulose and lignin
standards
• Investigation of cellulose and lignin using Pyrolysis Extractive Electrospray Ionization (Py-EESI)
References
1. Evans, R. J., Milne, T. A. Molecular Characterization of the Pyrolysis Biomass. 1. Fundamentals. Energ Fuel, 1987, 1, 123-137.
2. Lu, Q., Yang, X.-C., Dong, C.-Q., Zhang, Z.-F., Zhang, X.-M., Zhu, X.-F. Influence of pyrolysis temperature and time on the cellulose fast pyrolysis products: Analytical Py=GC/MS study. J Anal App Pyrol, 2011, 92, 430-438.
Acknowledgements
Thank you to R. J. Reynolds for funding this project
Glish Group