1. A m a n d a J a m e e r
S u p e r v i s o r : D r . D o n a l d R . H a s t i e
O c t o b e r 3 1 , 2 0 1 4
Evaluating the Utility of an Atmospheric
Pressure Chemical Ionization Mass
Spectrometer (APCI-MS/MS) at Detecting
Organic Peroxides
1

2. Presentation Outline
2
 Project goals
 What are organic peroxides?
 Formation in the atmosphere
 Importance of organic peroxides
 Previous and current detection methods
 Experimental set-up
 Results
 Future work

3. Project Goals
To evaluate the ability of a positive-ion atmospheric pressure chemical
ionization mass spectrometer ((+) APCI-MS) to detect organic peroxide
formation during β-pinene ozonolysis experiments
 How do organic peroxides behave in the APCI-MS/MS?
 What APCI-MS/MS analysis mode will be useful for organic peroxide
detection?
 Based on common features from mass spectra, can a “fingerprint” analysis
be developed for future applications?
3

4. What are Organic Peroxides?
 Compounds containing at least two oxygen atoms linked together
Where:
R1 = H atom or organic substituent
R = organic substituent
4
Hydroperoxide Peroxy acid
Peroxy ester Peroxy hemiacetal
Dialkyl peroxide
R
O
OH O
OH
R
1
O
R
1
OH
O
O
R
O
O
R
1
O
R
R
O
O
R

5. Formation in the Atmosphere – HO Radicals
 Generally formed through hydroxyl (HO) -initiated reactions
RH + HO· → R· + H2O
R· + O2 + M → ROO· + M
ROO· + HOO· → ROOH + O2
5
ROO· + NO· → RO· + NO2
ROO· + NO· → RONO2
ROO· + NO2
· → ROONO2

6. Formation in the Atmosphere – Ozone (O3)
 O3-initiated reactions with unsaturated hydrocarbons
6
R1R2
R3R4
O
O
+
O
-
R 2
R4
O
O
O
R1
R3
O
R3
R4
+ C
O
O
R1
R 2
O
R1
R2
+ C
O
O
R3
R4
a
b
c
Primary
Ozonide
Criegee
Intermediate
Criegee
Intermediate
R
2
C
O
O
R
1
R
4
C
O
O
R
3Primary
Ozonide
Criegee Biradical
Criegee Biradical

7. Criegee Biradical
+ H2O
R
1
R
2
O
OH
OH
Formation in the Atmosphere – Ozone (O3)
 Criegee biradical reacts with water vapour
7
R
2
C
O
O
R
1

8. Importance of Organic Peroxides
8
 Play an important role in the chemistry of the troposphere
 Organic peroxides are potential products from volatile organic compound
oxidation with hydroxyl (HO) radicals or ozone (O3)
 Organic peroxides are reservoirs for radicals
 These radicals help determine the lifetime of both natural and anthropogenic
hydrocarbons in the atmosphere
 May contribute to secondary organic aerosol (SOA) formation

9. Contribution to SOA
 Compounds with sufficiently low vapour pressure to be present in the particle
phase
 Organic peroxides are major components of SOA formed from alkene
ozonolysis
 Docherty et al., (2005) estimated that organic peroxides contributed ~ 47% and
~85% of SOA mass formed during α- and β-pinene oxidation experiments
respectively
9

10. Previous Detection Methods
 Colorimetric method for detecting hydrogen peroxide (H2O2)
 Chemiluminescent method for detecting and quantifying H2O2
 High performance liquid chromatography – Fluorescence method for detecting
and quantifying H2O2 and organic peroxides
 Tunable diode laser adsorption spectroscopy for detecting and quantifying
H2O2
10

11. Mass Spectrometry
 Can provide information about the molecular weight of a species
 Depending on the instrument set-up, can provide structural information of a
species
 On-line analysis
 Does not requires sample pre-treatment
 Require samples to be ionized before analysis
11

12. Detecting Organic Peroxides by Mass
Spectrometry
Chemical ionization mass spectrometry (CIMS) analysis
 Target neutral molecule is ionized through a series of collisions with a reagent
ion present in the ion source
 “Softer” ionization technique where ions are produced with little excess energy
 For example, Crounse et al., (2006) used CF3O- reagent ions to detect H2O2 and
peroxyacetic acid (PAA)
CF3O- + H2O2 CF3O-H2O2
CF3O- + PAA CF3O-PAA
12

13. Detecting Organic Peroxides by Mass
Spectrometry
 Baker et al., (2001) and Reining et al., (2009) used (H2O)H+ reagent ions to
detect organic peroxide formation from linear alkene and monoterpene
ozonolysis
M + (H2O)nH+ [M + H]+ + (H2O)n
 Organic peroxides containing a –OOH functional group were identified based
on a mass loss of 34 u (H2O2) from the [M + H] ion while performing tandem
mass spectrometry (MS/MS)
13

14. APCI-MS/MS
 Chemical ionization at atmospheric pressure conditions
q0 Q1 Q3q2
Triple quadrupole mass
spectrometer
Ion source
Purified air flow
Ionization reagent
(H2O)nH+
(CH3OH)nH+
Detector
14
Mass spectrum
33 43 55
m/z

15. Ion-Molecule Reactions in the Ion Source
 Most common ion-molecule reaction is proton transfer
Occurs if the proton affinity of M is greater than the proton affinity of R
 If the proton affinity between M and RH+ are similar…
Adduct formation
M + RH+ [M + H]+ + R
M + RH+ [M + RH]+
15

16. (+) APCI-MS/MS Analysis Modes
1. Full scan mode
2. Product-ion scan
mode Select Fragment Analyze
3. Neutral-loss scan
mode
FragmentScan Scan
“offset by x”
transmit
Scan
Q1 q2 Q3
16

17. A N A L Y S I S O F C O M M E R C I A L L Y A V A I L A B L E
O R G A N I C P E R O X I D E S T A N D A R D S
H o w d o o r g a n i c p e r o x i d e s b e h a v e i n t h e A P C I -
M S / M S ?
W h a t A P C I - M S / M S a n a l y s i s m o d e w i l l b e u s e f u l f o r
o r g a n i c p e r o x i d e d e t e c t i o n ?
Phase 1 of Project
17

18. Experimental Design for Standard Analysis
 Commercially available organic peroxides were analyzed neat or by preparing a
10% v/v solution in either water or methanol
M + (H2O)nH+ [M + H]+ + (H2O)n
[M + H2O + H]+
M + (CH3OH)nH+ [M + H]+ + (CH3OH)n
[M + CH3OH + H]+
Purified air flow
To dilu on flask
Syringe pump
To ion source M + 1
M + 19
M + 1
M + 33
18

19. Organic Peroxide Standard Selection
CH3
CH3
CH3
O
OH
CH3
CH3
CH3
O
O
CH3
CH3
CH3
CH3CH3
O
OH
CH3
O
O
OH
CH3
CH3
CH3
O
O
O
CH3
tert-butyl
hydroperoxide
di-tert-butyl
hydroperoxide
tert-butyl
peroxyacetate
peracetic acid
cumene
hydroperoxide
19

20. Results for Full Scan Analysis Mode
Ionization with Protonated Water (H2O)H+
 Mass spectra were dominated by fragment ion signals
 [M + H]+ or [M + H2O + H]+ ion signals not found in appreciable amounts
100
80
60
40
20
0
RelativeAbundance(%)
30025020015010050
m/z
73
181
tert-butyl hydroperoxide tert-butyl peroxyacetate
100
80
60
40
20
0
RelativeAbundance(%)
30025020015010050
m/z
265
73
20
m/z 91 or 108
m/z 133 or 151

21. Results for Full Scan Analysis Mode
Ionization with Protonated Methanol (CH3OH)H+
 Fragment ions were apparent in mass spectra
 Four out of five standards displayed a [M + CH3OH + H]+ ion signal
120
80
40
0
RelativeAbundance(%)
25020015010050
m/z
73
65
123
181
100
80
60
40
20
0
RelativeAbundance(%)
25020015010050
m/z
73
265
165
tert-butyl hydroperoxide tert-butyl peroxyacetate
21

22. Results for Neutral-Loss Scan Analysis
 Only three standards contained an –OOH functional group
 tert-butyl hydroperoxide, peroxyacetic acid and cumene hydroperoxide
CH3
CH3
CH3
O
OH
CH3
CH3
CH3
O
O
CH3
CH3
CH3
CH3CH3
O
OH
CH3
O
O
OH
CH3
CH3
CH3
O
O
O
CH3
tert-butyl
hydroperoxide
di-tert-butyl
hydroperoxide
tert-butyl
peroxyacetate
peracetic acid
cumene
hydroperoxide
22

23. Neutral-Loss Scan Analysis
Ionization with Protonated Water
100
80
60
40
20
0
RelativeAbundance(%)
28024020016012080
m/z ratio, amu
77
95
100
80
60
40
20
0
RelativeAbundance(%)
1501401301201101009080
m/z ratio, amu
93
77
91
75
107
m/z m/z
m/z
tert-butyl hydroperoxide peroxyacetic acid
cumene hydroperoxide
23
[M + H]+
[M + H]+
[M + H]+

24. Neutral-Loss Scan Analysis
Ionization with Protonated Methanol
tert-butyl hydroperoxide peroxyacetic acid
24
[M + H]+
[M + H]+

25. Water versus Methanol Results
Enthalpy of the Overall Gas-phase Protonation Reaction ( ΔH°reaction )
Compound PA (kJ/mol)
Water as Ionization
Reagent
Methanol as Ionization
Reagent
tert-butyl hydroperoxide 803 -107 -37
di-tert-butyl peroxide 790 -94 -24
cumene hydroperoxide >696
peracetic acid 783 -87 -17
peroxyacetate 791 -95 -25
25
M + (H2O)H+ [M + H]+ + H2O
M + (CH3OH)H+ [M + H]+ + CH3OH
ΔPA = PAionization reagent – PAstandard = - ΔH°reaction

26. Summary of Standard Analysis
How do organic peroxides behave in the APCI-MS/MS?
 Organic peroxides fragment or decompose after the ionization process
Excess energy owing to the large ΔPA values, inducing fragmentation
 Intact adduct ion only found when using methanol as an ionization reagent (i.e.
[M + CH3OH + H]+)
Less energy available to facilitate fragmentation since ΔPA values are small
26

27. Summary of Standard Analysis
What APCI-MS/MS analysis mode was useful for organic
peroxide detection?
 Full scan analysis mode provided a qualitative overview of the ions produced in
the ion source
Nothing “selective” about this analysis mode
 Neutral-loss scan analysis mode was useful at detecting ion signals that
represented a hydroperoxide or peroxy acid
A mass loss of 34 u was characteristic for organic peroxides containing a –OOH
functional group
27

28. S M O G C H A M B E R E X P E R I M E N T S
A p p l y k n o w l e d g e g a i n e d f r o m s t a n d a r d a n a l y s i s
A r e t h e r e a d d i t i o n a l c o m m o n m a s s l o s s c r i t e r i a t h a t
c a n b e u s e d t o s e l e c t i v e l y d e t e c t o r g a n i c p e r o x i d e s ?
Phase 2 of Project
28

29. Smog Chamber Experiments
 Ozonolysis experiments using β-pinene as the precursor hydrocarbon
 Naturally emitted hydrocarbon
 Monoterpene with the formula C10H16
 Is a significant source of SOA
29

30. Experimental Design for β-pinene Ozonolysis
MFC
Purified
Airflow
β-pinene
injection
Ozone
Generator
Compressed
Air
Smog Chamber Input
Pump
(+) APCI-
MS/MS
Ozone
Analyzer
8 m3 Smog chamber
Smog Chamber Output
MFM
30

31. (+) APCI-MS/MS Analysis Modes
31
1. Full scan mode
2. Product-ion scan
mode Select Fragment Analyze
3. Neutral-loss scan
mode
FragmentScan Scan
“offset by 34 u”
transmit
Scan
Q1 q2 Q3

32. Results for Ozonolysis Experiments
Ionization using Protonated Water
 Full Scan Mass Spectrum
 Odd number m/z values
 Nothing selective about this analysis mode
m/z
32

33. Results for Ozonolysis Experiments
Ionization with Protonated Water
 Neutral-loss Scan Mass Spectrum
 m/z values that lost 34 u during collision events
 Reduced complexity to a handful of m/z values
m/z
33
m/z values
171
173
187
201
203

34. Ionization with Protonated Methanol
34
 Chemical ionization using protonated water caused excessive fragmentation
during standard analysis
 Intact ions were observed during full scan analysis while using protonated
methanol as an ionization reagent
M + (CH3OH)H+ [M + CH3OH + H]+
M + 33
Can additional m/z values be observed in full scan mass
spectrum if protonated methanol is used as an ionization
reagent?

35. Results for Ozonolysis Experiments
35
Ionization with Protonated Methanol
 Full scan mass spectrum
 Odd number m/z values
 Appears similar to previous full scan mass spectrum using protonated water
100
80
60
40
20
0
RelativeAbundance(%)
40035030025020015010050
m/z ratio, amu
139
155
185
293
201
187
203
171
m/z m/z
Ionization with protonated waterIonization with protonated methanol

36. Results for Ozonolysis Experiments
36
Ionization with Protonated Methanol
 Neutral-loss mass spectrum
 m/z value capable of losing 34 u
 No additional m/z values observed
100
80
60
40
20
0
RelativeAbundance(%)
350300250200150100
m/z ratio, amu
187
171
173
203
m/z
Ionization with protonated methanol
m/z
Ionization with protonated water

37. Results for Ozonolysis Experiments
37
 No new information was obtained by using protonated methanol as an
ionization reagent
 Ozonolysis experiments continued using protonated water as an ionization
reagent
Can additional m/z values be observed in full scan mass
spectrum if protonated methanol is used as an ionization
reagent?

38. Product-Ion Scan Analysis
38
 m/z values 171, 173, 187, 201, and 203 were investigated further using product-
ion scan analysis mode
 Validate mass losses of 34 u and determine additional common mass losses
 Propose plausible structures based on observed losses and ozonolysis
mechanism

39. Product-Ion Mass Spectrum for m/z 187
39
100
80
60
40
20
0
RelativeAbundance(%)
1801601401201008060
m/z ratio, amu
187
169153
125
155
109
m/z
Losses observed
 18 u (H2O)
 32 u (O2)
 34 u (H2O2)
 62 u (H2O2 and CO)

40. Product-Ion Scan Analysis Summary
40
Neutral Loss Mass (u)
m/z 18 32 34 62
171 Yes Yes Yes Yes
173 Yes Yes Yes (minor) Yes (minor)
187 Yes Yes Yes Yes
201 Yes Yes (minor) Yes (minor) Yes
203 Yes Yes (minor) Yes Yes

41. Investigating Losses of 62 u
41
 Combined mass losses totaling 62 u
 Loss of H2O2 and CO
 Peroxy acids can explain these losses
O
OH
O
Cl
3-chloroperbenzoic acid
Hydroperoxide Peroxy acid
Peroxy ester Peroxy hemiacetal
Dialkyl peroxide
R
O
OH O
OH
R
1
O
R
1
OH
O
O
R
O
O
R
1
O
R
R
O
O
R

42. 3-chloroperbenzoic acid
42
 [M + H]+ and [M + CH3OH + H]+ were apparent in full scan mass spectrum
 Product-ion mass spectrum for m/z 173 showed major losses of 62 u
 Possible for peroxy acids to exhibit this mass loss during collision events
m/z m/z
Full Scan Mass Spectrum
Product-ion Mass Spectrum for
m/z 173

43. Proposed Structures
43
O
O
OH
CH3
CH3
CH3
CH3
O
O
O
OH
CH3
CH3
O OHOH
CH3
CH3
O
O
O
O
OH
CH3
CH3
O
OH
O
O
OH
CH3
CH3
O
O
OH
O
MW 170 MW 172
(a)
MW 172
(b)
MW 186 MW 200 MW 202

44. Summary for Smog Chamber Experiments
44
Are there additional common mass loss criteria that can be
used to selectively detect organic peroxides?
 Yes, product-ion mass spectra for organic peroxide candidates showed common
mass losses
Aside from mass losses of 34 u, mass losses of 32 and 62 u can be used to
selectively enhance the detection organic peroxides containing a –OOH functional
group

45. Project Summary
45
 (+) APCI-MS/MS can be used to selectively detect organic peroxides
 Required little to no sample treatment before analysis
 Tandem mass spectrometry analysis was useful to for selectively detecting
organic peroxides
 Neutral-loss analysis for 32, 34, and 62 u can be used as a criteria to observe
m/z values that were organic peroxide candidates

46. W h a t a r e t h e f u t u r e d i r e c t i o n s f o r t h i s p r o j e c t
k n o w i n g t h a t o r g a n i c p e r o x i d e s c a n b e s e l e c t i v e l y
d e t e c t e d b y t h e A P C I - M S / M S ?
46
Future Work

47. Future Work
47
 Factors that influence organic peroxide formation
Additional experiments under high and low NOx (NO + NO2) conditions
Relative humidity experiments
 Quantitative studies
Need standards that are representative of products formed in the smog chamber

48. Acknowledgements
48
Supervisor: Dr. Donald Hastie
Group members: Mehrnaz Sarrafzadeh and Zoya Dobrusin
Supervisory and exam committee members: Dr. R. McLaren, Dr. J. Rudolph, and
Dr. M. Gordon
CAC graduate students and postdocs
Carol Weldon from CAC
Greg Koyanagi from CRMS
IACPES
Charles Hantho and Harold Schiff Foundations