Oxidation products of terpenes:
synthesis of reference
compounds and novel sampling
technique
Jevgeni Parshintsev
Joonas Nurmi, Kari Hartonen and Marja-Liisa
Riekkola
University of Helsinki
Finland
Background
• Aerosols are relatively stable suspension
of solid or liquid particle in a gas, diameter
~0.002µm – 100 µm
• Either directly emitted into the
atmosphere or formed there by chemical
reactions (primary and secondary
aerosols)
Impact on the energy balance of
the planet
direct
-scattering &
-absorption of solar radiation
In the atmosphere
indirect
alter the:
-formation
-precipitation efficiency &
-optical properties of clouds
Aerosols are cooling the Earth’s
surface immediately below them
• Directly:
I
 e bext l
I0
Where I and I0 are the incident and transmitted light intensities respectively,
L is the pathlength of the light beam, and bext is the extinction coefficient,
(length)-1
bext  bg  b p
bext  bag  bsg  bap  bsp
Light extinctions due to gaseous and particulate absorption and scattering
BUT: light absorption by NO2(one,which contribute significantly) is usually much
Less than the total light scattering and absorption by particles
Scattering is significant if D≈λ
-and indirectly:
Aerosol particles are “seeds” to start the formation of
cloud droplets.
Aerosol concentration increase => the water gets spread
over many more particles => smaller drops
Clouds with smaller drop:
-reflect more sunlight
-such clouds last longer
Both effects increase the amount of sunlight that is
reflected to space without reaching the surface.
It is thought that aerosol cooling
may partially offset expected
global warming that is attributed
to increases in the amount of
carbon dioxide from human
activity…
Atmospheric aerosols
http://www.ems.psu.edu/~lno/Meteo437/Aerosol.jpg, 31.7.06
Why sesquiterpenes?
• ~9% of all non-methan VOCs in aerosols
• almost unknown (compare to monoterpenes)
• Have much higher aerosol potential than
monoterpenes. Example:
• 2% of total biogenic VOC- emission is assumed
to be β-caryophyllene in Scandinavian
atmosphere, the contribution by caryophyllene to
the total biogenic secondary aerosol formation
was estimated to be 12%!
C15H24
Analysis of sesquiterpenes
oxidation products
• Usually collected on impactor plate or filter
• Extracted by proper solvent
• Analyzed by GC-MS (derivatization is
needed if too polar)
• Identification & quantitation are almost
impossible nowadays because of:
• Leak of reference materials, small
amounts & great variety
Conventional collection techniques
• Impactor, filter (usually quartz)
http://jolisfukyu.tokai-sc.jaea.go.jp/fukyu/tayu/ACT03E/img/09IMG/09_01.jpg
http://www.menlh.go.id/apec_vc/osaka/eastjava/hap_en/filter/5-3.gif 18.11.07
Synthesis, isolation
• Solution of β-caryophyllene (~1000ppm) in
dichloromethane was ozonolyzed by bubbling the ozone
(produced by corona discharge) through the mixture
• Reaction was stopped when potassium iodide solution
trap turned yellow (unreacted ozone, reaction time appr.
2h) O3  2KI  H2O  I2  2KOH  O2
• 100 mg of Zn-powder and 10 ml of acetic acid/water
mixture was added and refluxed for 1h
• Compounds were extracted by LLE to the
dichloromethane
• Products were isolated and purified by flashchromatography
Scheme of oxidation of β-caryophyllene
Paineistettu
pylväskromatografialaitteisto
Identification
• Mass-spectrometry with ESI- and EIionization and nuclear magnetic
resonance spectroscopy were applied
Structures
O
H3C
O
10
11
H3C
O
12
11
H2C
4
9
10
3
8
9
H
H3C
7
H3C
6
3
4
5
H
5
2
H
1
O
5
H3C
8
H3C
7
6
H
6
Picture 1. Structures of β-nocaryophyllone aldehyde (left) and
β-caryophyllene aldehyde (right) confirmed by NMR.
2
1
O
Analysis of aerosol samples
• Self made standards were used in the
analysis of ambient aerosol samples
collected in Hyytiälä in 2003
• GC-MS and GC*GC-FID were used
• β-nocaryophyllone aldehyde was positively
identified in one sample with amount of
17ng/m3
Parshintsev et al. accepted to Analytical and Bioanalytical Chemistry
Conclusions I
• Two β-caryophyllene oxidation products were
synthesized, isolated and analyzed for the precise
structures for the first time
• Standards were used in analysis of ambient aerosol
samples
• Presence of studied compounds in the samples proves
their participation in biogenic aerosol formation
• However, more oxidation products of terpenes should be
synthesized, to make their analysis possible, in order to
understand the contribution of sesquiterpenes oxidation
products to the biogenic aerosol chemistry
Part II. Working principles of PILS
• particle growth in a mixing condensation
particle counter
• droplet collection by a single jet inertial
impactor
• used off-line, but continuous sample flow
can provide on-line applications through
SPE to HPLC or directly to API-MS
PILS
Weber et al. Aerosol Science and Technology 35: 718–727 (2001)
PILS
• Sample air flow 16.7 L/min (can be
increased)
• Transport flow can be changed to
relatively unpolar solvent
• Size separation before PILS, such as
virtual impactor
• Gases removed by KOH, H3PO4, XADdenuders
Disadvantages
• Needs to be cleaned frequently (can be
automated by running methanol/water
steam through the system)
• 10% of gases passes through the
denuders => “zero” samples should be run
often
Aerosol sampling
• Samples were collected during spring and
summer 2007 in Hyytiälä (SMEARIIstation), Finland
• Filter sampling was used as reference
• Samples were analyzed off-line: LLE to
dichloromethane, concentration, GC-MS
Parshintsev et al. (2007) Manuscript in preparation
Preliminary results
• Pinonaldehyde was found in all samples in
great amounts
• Correlation with even/non-event was
noticed due to the better time resolution
• Quantitation of other compounds is in
progress
Comparison with filter sampling
• Two hours filter samples showed amounts
under LOD
• Only day or night samples contained
amounts exceeding LOD
Event week (except 103)
70,00
60,00
50,00
40,00
30,00
20,00
10,00
0,00
102,00
103,00
104,00
105,00
106,00
107,00
108,00
109,00
Non-event week
70,00
60,00
50,00
40,00
30,00
20,00
10,00
0,00
113,00
114,00
115,00
116,00
117,00
118,00
119,00
Conclusions II
• Time resolution of PILS is better than of
filter sampling
• Less artifacts
• On-line possibility
• Transport flow can be 2-propanol
(improves the collection efficiency for less
polar compounds)
• However, optimization is still needed