1. Objective  To develop methods for analysis of compounds in organic aerosol particles Why is this important?  Environmental impact  Alternative fuels  Human health impact  Forensics

2. Experimental Design  Analytical Goals: »Detect compounds from aerosol particles in real time »Infer information about molecule structure »Develop an analytical method capable of interrogating a variety of organic and inorganic compounds  Mass spectrometry is an ideal analytical technique to accomplish these goals because of its speed, sensitivity, and selectivity

3. How it Works Generic Mass Spectrometer Components Our Design Pyrolysis (Py) Extractive Electrospray Ionization (EESI) Quadrupole Ion Trap Computer Sample Prep Ion Source Analyzer Ion Detector Data System Vacuum Chamber Generate analyte of interest Create ions that can be manipulated Separate and detect ions in time based on their mass-to-charge ratio Correlate time of detection to mass-to-charge ratio and view the results Ion Detector Vacuum Chamber

4. Selection of the Analyte of Interest  The pyrolysis product of cellulose contains many compounds; some with similar mass to charge ratios  Levoglucosan has been previously identified as a known pyrolysis product of cellulose 145 163 185 205 223 265 307 0 2 4 6 100200300400500m/z Intensity x 10 4 Py-EESI-MS of Pyrolyzed Cellulose [Levoglucosan+H] +

5. Collision Induced Dissociation (CID)  Collision induced dissociation is a process used to differentiate between ions of the same mass-to-charge ratio.  Ions are subjected to collisions with neutral gas particles.  Structural information about the molecule can inferred based on the dissociation pathways N P + P + gains energy from collision N and P + collide P 1 + P 3 + P 2 + P 4 + P + dissociates into fragment ions N

6. CID of Protonated Levoglucosan  Many ions undergo a neutral loss of water, making it an uninformative neutral loss  The addition of water to the ion is an uncommon reaction  The rate of reaction of water with an ion is indicative of ion structure Intensity x 10 4 145 163 181 0 2 4 6 140150160170180m/z + H 2 O - H 2 O MS/MS 163

7. Kinetics of Reactions

8. Increase in Products with Longer Reaction Time Reaction Time: 0 ms Reaction Time: 300 ms Reaction Time: 600 ms Reaction Time: 900 ms 163 181 0 25 50 75 100 163 181 195 0 25 50 75 100 163 181 0 25 50 75 100 Levoglucosan + methanol - water? Levoglucosan Levoglucosan + water Levoglucosan + methanol?

9. Integrated Rate Laws Time [A t ] x x x x x xx Time ln[A t ] x x x x x x x  The experimentally determined slope of the integrated rate law gives the rate constant

10. Kinetics of Adduction of Water to Levoglucosan  The concentration of water is much higher than the concentration of [Levoglucosan+H] +  The kinetics of the reaction are dictated by the concentration of [Levoglucosan+H] + EESI Solvent: 50/49/1 Methanol/Water/Acetic Acid

11. Is the Water from the EESI Solvent?  Decreasing the concentration of water at the inlet to the mass spectrometer may decrease the amount water available in the ion trap for adduction  Changing the composition of the EESI solvent influences the extent of reaction  Use 99/1 Acetonitrile/Acetic Acid as EESI solvent

12. Influence of Changing Solvent Composition Reaction Time: 0 ms Reaction Time: 300 ms Reaction Time: 600 ms Reaction Time: 900 ms 163 0 25 50 75 100 163 0 25 50 75 100 163 0 25 50 75 100 163 0 25 50 75 100 150155160165170175180185190195m/z No increase in relative intensity of m/z 181

13. Water from the EESI Solvent  No water adducts are observed when 99/1 Acetonitrile/Acetic Acid is used as an EESI solvent  Water in the ion trap may be due to the high concentration of water vapor at the inlet of the mass spectrometer from the EESI solvent  Replace water in the EESI solvent with D 2 O to generate D 2 O adduct at m/z 183

14. Replacing H 2 O with D 2 O in EESI Solvent  The effect of D 2 O on the appearance of the mass spectrum is not as significant as expected »The relative intensity of [M+D] + (m/z 164) only increases by a small amount »The relative intensity of the D 2 O adduct (m/z 183) does not increase significantly MS Scan of 50/49/1 MeOH/H 2 O/AA 145 155 163 177 181 0 1 2 3 4 Intensity x 10 4 145 149 159 163 177 181 0 2 4 6 140145150155160165170175180 m/z MS Scan of 50/49/1 MeOH/D 2 O/AA

15. Two Ion Structures Are Present  The integrated rate law is not linear over the entire reaction time range  Indicates the presence of two structures of levoglucosan with different reaction kinetics  After 400 ms, all of structure 1 has reacted; structure 2 is non-reactive with water

16. Discussion of Reactive Ion Structures  EESI of levoglucosan with 50/49/1 Methanol/H 2 O/Acetic Acid generates one ion structure that reacts with water  k is approximately 50% larger for the reactive structure formed when H 2 O is in used in the EESI solvent rather than D 2 O  The difference between the rate constants for the adduction of water with levoglucosan ionized using EESI solvent containing D 2 O vs. H 2 O indicates that the reactive ion structures are not the same

17. Discussion of Non-Reactive Ion Structures  When EESI is performed using 99/1 Acetonitrile/Acetic Acid the ions generated do not react with water  When D 2 O is used in place of H 2 O in the EESI solvent, a second ion structure that does not react with water is generated  Collision induced dissociation can be used to interrogate the structure of the observed ions

18. EESI Solvent Dictates Ion Structure 163 145181 163 181163 145181 163 145181 50/49/1 Methanol/H 2 O/Acetic Acid 163 105 81 121 99/1 Acetonitrile/Acetic Acid 163 181 145 50/49/1 Methanol/D 2 O/Acetic Acid The levoglucosan ion (m/z 163) from 99/1 Acetonitrile/Acetic Acid exhibits a different CID pattern than the ion from 50/49/1 Methanol/D 2 O/Acetic Acid, suggesting that the non-reactive structures are not the same

19. Conclusions  Certain structures of protonated levoglucosan undergo pseudo-first order reactions with water  Water is present as a background neutral in the vacuum system  Changing the composition of EESI solvent changes the structure of the ions generated  At least 3 ion structures were observed for protonated levoglucosan, depending on EESI solvent

20. Acknowledgements Thank you to R. J. Reynolds for funding this project Glish Group