defense presentation 2014 october 14 new

Amanda JameerSuperv i sor : Dr. Donald R . Hast ie

October 31 , 2014

Evaluating the Utility of an Atmospheric Pressure Chemical Ionization Mass

Spectrometer (APCI-MS/MS) at Detecting Organic Peroxides

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Presentation Outline

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

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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?

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What are Organic Peroxides?

Compounds containing at least two oxygen atoms linked together

Where:

R1 = H atom or organic substituent

R = organic substituent

Hydroperoxide Peroxy acid

Peroxy ester Peroxy hemiacetal

Dialkyl peroxide

R

O

OH O

OH

R1

O

R1

OH

O

O

RO

O

R1

O

R

R

O

O

R

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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

ROO· + NO· → RO· + NO2

ROO· + NO· → RONO2

ROO· + NO2· → ROONO2

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Formation in the Atmosphere – Ozone (O3)

O3-initiated reactions with unsaturated hydrocarbons

R4

C

O

O

R3Primary

Ozonide

Criegee Biradical

Criegee Biradical

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Criegee Biradical

+ H2OR1

R2

O

OH

OH

Formation in the Atmosphere – Ozone (O3)

Criegee biradical reacts with water vapour

R2

C

O

O

R1

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Importance of Organic Peroxides

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

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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

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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

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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

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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

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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)

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APCI-MS/MS

Chemical ionization at atmospheric pressure conditions

q0 Q1 Q3q2

Triple quadrupole mass spectrometer

Ion source

Purified air flowIonization reagent

(H2O)nH+

(CH3OH)nH+

Detector

Mass spectrum

33 43 55

m/z

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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]+

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(+) APCI-MS/MS Analysis Modes

1. Full scan mode

2. Product-ion scan mode Select Fragmen

tAnalyze

3. Neutral-loss scan mode

Fragment

Scan Scan“offset by x”

transmitScan

Q1 q2 Q3

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ANALYSIS OF COMMERCIALLY AVAILABLE ORGANIC PEROXIDE STANDARDS

How do o rgan i c pe rox ides behave i n the APCI -MS/MS?

What APCI -MS/MS ana l ys i s mode w i l l be use fu l f o r o rgan i c pe rox ide de tec t i on?

Phase 1 of Project

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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]+

M + 1

M + 19

M + 1

M + 33

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Organic Peroxide Standard Selection

CH3 CH3

CH3 OOH

CH3 CH3

CH3 OO

CH3

CH3 CH3CH3CH3

OOH

CH3

O

OOH

CH3

CH3

CH3

OO

O

CH3

tert-butyl hydroperoxide

di-tert-butyl hydroperoxide

tert-butyl peroxyacetate

peracetic acid

cumene hydroperoxide

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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

tert-butyl hydroperoxide tert-butyl peroxyacetate

m/z 91 or 108

m/z 133 or 151

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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

tert-butyl hydroperoxide tert-butyl peroxyacetate

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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 OOH

CH3 CH3

CH3 OO

CH3

CH3 CH3CH3CH3

OOH

CH3

O

OOH

CH3

CH3

CH3

OO

O

CH3

tert-butyl hydroperoxide

di-tert-butyl hydroperoxide

tert-butyl peroxyacetate

peracetic acid

cumene hydroperoxide

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Neutral-Loss Scan AnalysisIonization with Protonated Water

m/z m/z

m/z

tert-butyl hydroperoxide peroxyacetic acid

cumene hydroperoxide

[M + H]+

[M + H]+

[M + H]+

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Neutral-Loss Scan AnalysisIonization with Protonated Methanol

tert-butyl hydroperoxide peroxyacetic acid

[M + H]+

[M + H]+

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Water versus Methanol Results

Enthalpy of the Overall Gas-phase Protonation Reaction ( ΔH°reaction )

CompoundPA

(kJ/mol)

Water as Ionization Reagent

Methanol as Ionization Reagent

tert-butyl hydroperoxide 803 -107 -37

di-tert-butyl peroxide 790 -94 -24cumene

hydroperoxide >696   peracetic acid 783 -87 -17peroxyacetate 791 -95 -25

M + (H2O)H+ [M + H]+ + H2O

M + (CH3OH)H+ [M + H]+ + CH3OH

ΔPA = PAionization reagent – PAstandard = - ΔH°reaction

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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

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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

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SMOG CHAMBER EXPERIMENTS

App ly knowledge ga ined f rom s tandard ana l ys i s

Are the re add i t i ona l common mass l o ss c r i t e r i a tha t can be used to se l ec t i ve l y de tec t

o rgan i c pe rox ides?

Phase 2 of Project

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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

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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

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(+) APCI-MS/MS Analysis Modes

1. Full scan mode

2. Product-ion scan mode Select Fragmen

tAnalyze

3. Neutral-loss scan mode

Fragment

Scan Scan“offset by 34 u”

transmitScan

Q1 q2 Q3

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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

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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

m/z values

171173187201203

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Ionization with Protonated Methanol

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?

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Results for Ozonolysis Experiments

Ionization with Protonated Methanol

Full scan mass spectrum Odd number m/z values Appears similar to previous full scan mass spectrum using protonated water

m/z m/z

Ionization with protonated waterIonization with protonated methanol

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Results for Ozonolysis Experiments

Ionization with Protonated Methanol

Neutral-loss mass spectrum m/z value capable of losing 34 u No additional m/z values observed

m/z

Ionization with protonated methanol

m/z

Ionization with protonated water

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Results for Ozonolysis Experiments

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?

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Product-Ion Scan Analysis

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

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Product-Ion Mass Spectrum for m/z 187

m/z

Losses observed

18 u (H2O) 32 u (O2) 34 u (H2O2) 62 u (H2O2 and CO)

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Product-Ion Scan Analysis Summary

Neutral Loss Mass (u)

m/z 18 32 34 62

171 Yes Yes Yes Yes

173 Yes YesYes

(minor)Yes

(minor)

187 Yes Yes Yes Yes

201 YesYes

(minor)Yes

(minor) Yes

203 YesYes

(minor) Yes Yes

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Investigating Losses of 62 u

Combined mass losses totaling 62 u Loss of H2O2 and CO Peroxy acids can explain these losses

3-chloroperbenzoic acid

Hydroperoxide Peroxy acid

Peroxy ester Peroxy hemiacetal

Dialkyl peroxide

R

O

OH O

OH

R1

O

R1

OH

O

O

RO

O

R1

O

R

R

O

O

R

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3-chloroperbenzoic acid

[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

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Proposed Structures

O

OOH

CH3

CH3

CH3

CH3O

O

OOH

CH3

CH3

O OHOH

CH3

CH3O

O

O

O

OH

CH3CH3

O

OH

OO

OH

CH3

CH3

OOOH

O

MW 170 MW 172 (a)

MW 172 (b)

MW 186 MW 200 MW 202

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Summary for Smog Chamber Experiments

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

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Project Summary

(+) 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

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What a re the fu tu re d i r ec t i ons f o r th i s p ro jec tknowing tha t o rgan i c pe rox ides can be

se l ec t i ve l y de tec ted by the APCI -MS/MS?

Future Work

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Future Work

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

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Acknowledgements

Supervisor: Dr. Donald HastieGroup 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 postdocsCarol Weldon from CAC

Greg Koyanagi from CRMS IACPES

Charles Hantho and Harold Schiff Foundations