Determination of carbonyl compounds from Determination of carbonyl compounds from monoterpene oxidation using the IfT chambermonoterpene oxidation using the IfT chamber

Ariane Kahnt

23.06.2008

Leibniz-Institut für Troposphärenforschung

Permoserstr. 15

04318 Leipzig, Germany

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Content

1. Introduction

2. Experimental

3. Method development for carbonyl compound analysis

4. In-situ derivatisation of carbonyl compounds on DNPH-

coated denuders

5. First results from gas- and particle-phase analysis

6. Further improvement

7. Summary

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Introduction

- Monoterpenes are biogenic volatile organic compounds (BVOC)

- Emission from various plants and coniferyl trees

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Introduction

- Estimated global emission of volatile organic compounds (VOC): 1150 Tg C/year (Guenther et al. 1995): comprised of

- 44 % isoprene

- 11 % monoterpenes

- BVOC emission exceed those of anthropogenic compounds by a factor of ~10.

- Most BVOCs are more reactive than many anthropogenic non-methane volatile organic compounds (NMVOC)

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Introduction

Monoterpenes

- C10H16-skeleton

-pinene -pinene limonene 3-carene camphene sabinene

- Act as repellent, Pheromone for insects

- Most abundant monoterpenes emitted are -pinene, -pinene and limonene

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Introduction

- Atmospheric degradation of monoterpenes includes reactions with NO3, OH radicals and O3

- Oxidation leads to multifunctional oxidation products with low vapour pressure

- Their condensation and coagulation-processes lead to particle formation / growth (formation of secondary organic aerosol = SOA)

- SOA scatters solar radiation and can act as cloud condensation nuclei

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Introduction

Challenge:

- SOA formation is complex and not well known

- Composition of SOA is largely unknown

Motivation:

- Emission of BVOC is driven by climate (temperature, light)- Atmospheric oxidation leads to products that effect climate - Get more information about the oxidative decomposition of

monoterpenes

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Introduction

- Monoterpene oxidation produces semivolatiles and (or) multifunctional compounds such as carbonyl compounds and caboxylic acids

- Carbonyls play an important role in photochemical reactions

- Carbonyl compounds undergo photolysis and react with OH and NO3

radicals

- Some of them partition between the gas- and particle-phases

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Introduction

Mainly first oxidation products from monoterpenes are oxo-compounds(aldheydes and ketones)

Their reactions are not well characterised

- What are the next oxidation products?- What are their yields?- What are the mechanisms?

The challenge is:

- Carbonyl compounds are hard to sample and analyse

- Not all reaction products are available for positive identification and quantification

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Introduction

Examples of aldehydes originating from monoterpenesExamples of aldehydes originating from monoterpenes

Campholenic aldehyde

Endolim (from limonene)

Nopinon (from β-pinene)

Pinonaldehyde (from -pinene)

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Experimental

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Experimental

Aerosol chamber at the IfT (LEAK – „Leipziger Aerosol Kammer“)

- Overall chemistry in the atmosphere is far complex- Chamber studies provide a better understanding of atmospheric

reactions - Controlled parameters

LEAK („Leipziger Aerosol Kammer“ at the IfT)

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Experimental

Characteristics of the IfT chamber

- Made of Teflon® foil

- Cylindrical geometry

- Volume: 19 m3

- Surface/volume ratio: 2.1 m-1

- 60 UV-lamps

- Thermostat

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Experimental

Analysis of carbonyl compounds

- Polar carbonyl group

- Some carbonyls can partially or completely pass the sampling or analytical technique

- Derivatisation is necessary: e.g. with 2,4-Dinitrophenylhydrazine (DNPH)

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Experimental

- DNPH is a derivatisation reagent for aldehyde- and keto-groups

- Precipitation reagent

- Well known method for the identification of aldehydes and ketons by the melting points of the formed hydrazones (Brady 1931; Allen 1937)

- The formed hydrazones are:

- Coloured. This makes them detectable with UV-spectroscopy

- Easily ionisable using electrospray ionisation (ESI). This makes them detectable with HPLC/ESI-MS.

solution of DNPH addition of a carbonyl compound

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Experimental

Analysis of the hydrazones:

HPLC-UV coupled with ESI-TOFMS

HPLC (high performance liquid chromatography):

- Separation of compounds based on their distribution between a stationary phase (column) and a mobile phase (eluent)

- Depending on their affinity to the phases. The compounds are eluted at certain time

ESI-TOFMS (Electrospray Ionisation Time-Of-Flight Mass Spectrometry) - Ionisation of the compounds by electrospray- Formed ions are accelerated in an electric field - The velocity of ions depends on mass to charge ratios (m/z); hence the

mass to charge ratios of the analyte ions can be calculated from the time required for the ions to reach a detector

- TOF-MS is a high resolution mass spectrometer

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Experimental

First Step

Method development for standard compounds

- Available or synthesised monoterpene oxidation products were derivatised:

- Campholenic aldehyde- Endolim- Nopinone- Pinonaldehyde

to form the respective hydrazone

- Analysis and characterisation with HPLC/ESI-TOFMS

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Results from the method development of

carbonyl compound analysis

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Method development for carbonyl analysis

Hydrazone standard Structure M [g/mol]

Benzaldehyde-DNPH

C13H10N4O4

286

Campholenic aldehyde-DNPH

C16H20N4O4

332

Endolim-di-DNPH

C22H24N8O8

528

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Method development for carbonyl analysis

Hydrazone standard Structure M [g/mol]

Nopinon-DNPH

C15H18N4O4

318

Pinonaldehyde-di-DNPH

C22H24N8O8

528

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Method development for carbonyl analysis

Standard-Hydrazone-Mix

Benzaldehyde (m/z 285), Pinonaldehyde (m/z 527)

Nopinon (m/z 317), Campholenic aldehyde (m/z 331), Endolim (m/z 527)

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Method development for carbonyl analysis

Characterisation of the analytical method

Hydrazone standard RT

[min]

R2 LOD

[g/ml]

RSD

[%]

Benzaldehyde 11.4 0.9979 0.012 2.49

Campholenic aldehyde

14.2 0.9970 0.024 3.56

Endolim 15.1 0.9956 0.097 9.53

Nopinon 13.5 0.9993 0.072 2.87

Pinonaldehyde 15.1 0.9943 0.005 8.71

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Method development for carbonyl analysis

Suitable method regarding:

- chromatographic separation

(except the isobaric hydrazones of endolim and pinonaldehyde)- sensitivity

- stability

TOFMS allows the determination of exact chemical formula also for

unknown compounds due to its high sensitivity

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Method development for carbonyl analysis

- To collect also small carbonyl compounds which can not be collected with resin based denuder-sampling, on-tube derivatisation is performed

Use of annular denuders:

Advantages:

- Larger sampling capacity

- Operate at higher sample flow rates

Disadvantage:

- Diffusion equation not

characterised

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Method development for carbonyl analysis

Coated Denuders

- With the adsorbent XAD-4 as a collection surface

- Additional with DNPH + H3PO4 for the on-tube conversion of carbonyl compounds

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In-situ derivatisation of carbonyl compounds on DNPH-coated denuders

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In-situ derivatisation of carbonyl compounds on DNPH-coated denuders

- First compound: campholenic aldehyde

- Chamber experiments with different concentration of campholenic aldehyde

- Sampling with the DNPH-coated denuder

- Denuder extraction

- Analysis with the developed HPLC/ESI-TOFMS method

injected concentration [ppb]

10

40

80

160

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In-situ derivatisation of carbonyl compounds on DNPH-coated denuders

Gas-phase calibration of campholenic aldehyde on DNPH-coated denudersGas-phase calibration of campholenic aldehyde on DNPH-coated denuders

y = -2.3119x2 + 790.87x - 5040.1

R2 = 0.9971

0

10000

20000

30000

40000

50000

60000

70000

0 50 100 150 200

injected amount [ppb]

area

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- Cleaning procedure is necessary to remove the acid

- Should be done directly after the experiment

SPE (solid phase extraction)

OasisOasis®® HLB cartridges HLB cartridges

with a Hydrophilic-Lipophilic-Balanced sorbent

- Reversed phase polymer sorbent

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First results from gas- and particle-

phase analysis

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Results from gas- and particle-phase analysis

Chamber experiment -pinene

Initial HC concentration [ppb]

100

O3 60

RH [%] ~ 50

T [°C] 21±1

Reaction time [h] 2.5

Sampling time [h] 1

Seed particle NH4HSO4

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Results from gas- and particle-phase analysis

Filter Extract: particle-phase products

- Identification of the hydrazones from formaldehyde (m/z 209)

and pinonaldehyde (m/z 527)

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Results from gas- and particle-phase analysis

Denuder Extract: gas-phase products

- Identification of the hydrazones from formaldehyde (m/z 209), acetone (m/z 237) and pinonaldehyd (m/z 527)

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Results from gas- and particle-phase analysis

Preliminary quantitative result

Yield by mass References

Pinonaldehyde Gas-phase: 0.24

Particle-phase: 0.01

0.51±0.06 Hatakeyama et al. (1989)

0.19±0.04 Hakola et al. (1994)

0.06±0.19 Yu et al. (1999)

0.164±0.029 Baker et al. (2002)

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Further improvement

Further characterisation of in-situ derivatisation on denuders has to be

done to improve quantification:

- Denuder properties (e.g. variation between duty cycle, variability between different denuders)

- SPE method (recovery)

- More standards need to be prepared (HCHO, acetone etc...)

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Summary

- An HPLC-ESI-TOFMS method was developed for some first generation monoterpene oxidation products

(endolim, nopinon, pinonaldehyde)

- In-situ derivatistion on DNPH-coated denuders with campholenic aldehyde was performed and show a very good collection efficiency

- From the ozonolysis experiment of -pinene several carbonyl compounds were identified.

The yield of pinonaldehyde in the gas- and particle-phase was determined

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Acknowledgements

- Organiser of the summer school

- EUCAARI

(European Commission grant number 036833)

- IfT chamber team

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End

Thank You

very much

for your attention!

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Derivatisation with 2.4-Dinitrophenylhydrazine

- Gives coloured hydrazones (UV detection possible!)

- Detection at the wavelength near the absorption maxima of the respective hydrazone (360 nm)

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Oasis® HLB cartridges

- Contain a reversed phase sorbent (Hydrophilic-Lipophilic-Balanced)- Copolymer with aligned ratio of hydrophilic (N-Vinylpyrrolidone) and

lipophilic compound (Divinylbenzene)- Robust (pH)

General procedure:

- Coloumn solvation with methanol. water. acetonitrile- Coloumn conditioning with the sample medium- Sample loading- Coloumn washing with water- Target compound elution with acetonitrile

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Conditions for HPLC-UV-ESI-TOFMS analysis

Column Phenomenex® Gemini C6 Phenyl (3.5 µm.150 x 2 mm)

Eluents 0.2 % acetic acid in water (A)and 0.2 % acetic acid in acetonitrile (B) (programme: 70% A to 10% in 15 min)

Flow rate 0.5 ml/min

Sample injection 10 µl

Mass calibration 0.2 % acetic acid/5 mM NaOH in 50/50 (v/v %) in water/i-propanol solution at thebeginning of analysis