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