A sensitive method for the quantification of acrolein and other volatile carbonyls in ambient air

Article abstract of DOI:10.1021/ac051947s

Acrolein, an unsaturated aldehyde found in both indoor and outdoor air, is considered one of the greatest non-cancer health risks of all organic air pollutants. Current methods for determining acrolein often employ sorbent-filled cartridges containing a c

Full text of DOI:10.1021/ac051947s

Anal. Chem. 2006, 78, 2405-2412
A Sensitive Method for the Quantification of
Acrolein and Other Volatile Carbonyls in Ambient
Air
Vincent Y. Seaman, M. Judith Charles, and Thomas M. Cahill*
Department of Environmental Toxicology, University of California, Davis, One Shields Avenue, Davis, California 95616
Acrolein, an unsaturated aldehyde found in both indoor
and outdoor air, is considered one of the greatest non-
cancer health risks of all organic air pollutants. Current
methods for determining acrolein often employ sorbent-
filled cartridges containing a carbonyl derivatizing agent
to be one of the most dangerous components of toxic air
mixtures,5 acrolein is often omitted from studies of carbonyls
-7
8-18
in the atmosphere
or is reported as “below the limit of
detection”.1
5,19
The current EPA method of determining acrolein (method TO-
11A) is based on the well-documented reaction between carbonyls
and dinitrophenylhydrazine (DNPH), which produces hydrazones
(
e.g., dinitrophenylhydrazine). These methods are of
limited use for unsaturated compounds due to the forma-
tion of unstable derivatives, coelution of similar com-
pounds, long sample collection times, and ozone inter-
ferences that result in poor sensitivity, selectivity, and
reproducibility. The goal of this research was to develop
an analytical method for determining ppt concentrations
of acrolein and other carbonyls in air with short sampling
times (10 min). The method uses a mist chamber to
collect carbonyls by forming water-soluble carbonyl-
bisulfite adducts. The carbonyls are then liberated from
the bisulfite, derivatized, and quantified by gas chroma-
tography/electron capture negative ionization mass spec-
trometry. The method was applied to determine atmo-
spheric acrolein concentrations at three sites in northern
California reflecting hemispheric background concentra-
tions, biogenic-dominated regions, and urban environ-
that are separated by high-pressure liquid chromatography and
detected by UV spectrophotometry (HPLC-UV).2
0-22
While this
method is effective for many aldehydes and ketones, it has not
proven reliable for acrolein and other unsaturated carbonyls.
Numerous problems inherent in the methodology have been
reported, including instability of the DNPH-acrolein hydrazone
during collection and storage2
1,23-28
and poor chromatographic
(
5) U.S. Environmental Protection Agency. Integrated Risk Information System,
Acrolein (CASRN 107-02-8); 2003.
(6) Tam, B. N.; Neumann, C. M. J. Environ. Manage. 2004, 73, 131-145.
(
(
(
7) State of California, A. R. B.; California Air Resources Board: Sacramento,
1997; pp 1997-1911-1912.
8) van Leeuwen, S. M.; Hendriksen, L.; Karst, U. J. Chromatogr., A 2004, 1058,
107-112.
9) Pereira, E. A.; Rezende, M. O. O.; Tavares, M. F. J. Sep. Sci. 2004, 27,
28-32.
(10) Pereira, E. A.; Carrilho, E.; Tavares, M. F. J. Chromatogr., A 2002, 979,
ments. The resulting acrolein concentrations were 0.056,
409-416.
3
(11) Brombacher, S.; Oehme, M.; Dye, C. Anal. Bioanal. Chem. 2002, 372, 622-
29.
12) Pires, M.; Carvalho, L R. F. Anal. Chim. Acta 1998, 367, 223-231.
(13) Grosjean, E.; Grosjean, D. Int. J. Environ. Anal. Chem. 1995, 61, 343-360.
0
.089, and 0.29 µg/m , respectively, which are all above
6
3
the EPA Reference Concentration of 0.02 µg/m . The
minimum detection limit of 0.012 µg/m is below that of
(
3
(14) Shibamoto, Y. A. J. Chromatogr., A 1994, 672, 261-266.
other published methods. Methacrolein, methyl vinyl
ketone, crotonaldehyde, glyoxal, methyl glyoxal, and ben-
zaldehyde were also quantified.
(15) Coutrim, M. X.; Nakamura, L. A.; Collins, C. H. Chromatographia 1993,
3
7, 185-190.
(16) Zhang, J. F.; He, Q. C.; Lioy, P. J. Environ. Sci. Technol. 1994, 28, 146-
52.
1
(
17) Sax, S. N.; Bennett, D. H.; Chillrud, S. N.; Kinney, P. L.; Spengler, J. D. J.
Acrolein, a highly reactive R,â-unsaturated aldehyde, is a
Exposure Anal. Environ.Epidemiol. 2004, 14, S95-S109.
pulmonary toxicant and a common constituent of both indoor and
(18) Bakeas, E. B.; Argyris, D. I.; Siskos, P. A. Chemosphere 2003, 52, 805-
1,2
813.
outdoor air. Acrolein is produced by the incomplete combustion
of organic material as well as the oxidation of atmospheric
chemicals such as 1,3-butadiene, which is a primary component
of motor vehicle exhaust. Indoor sources of acrolein include
heated cooking oil, cigarette smoke, incense, candles, and wood-
burning fireplaces.3 Although considered by regulatory agencies
(
19) Grosjean, E.; Grosjean, D.; Fraser, M. P.; Cass, G. R. Environ. Sci. Technol.
996, 30, 2687-2703.
(20) Lipari, F.; Swarin, S. J. J. Chromatogr. 1982, 247, 297-306.
1
(
(
(
21) Tejada, S. B. Int. J. Environ. Anal. Chem. 1986, 26, 167-185.
22) Grosjean, D. Environ. Sci. Technol. 1982, 16, 254-262.
23) Kieber, R. J. a. K. M. Environ. Sci. Technol. 1990, 24, 1477-1481.
,4
(24) Goelen, E.; Lambrechts, M.; Geyskens, F. Analyst 1997, 122, 411-419.
(
25) Schulte-Ladbeck, R.; Lindahl, R.; Levin, J. O.; Karst, U. J. Environ. Monit.
*
To whom correspondence should be addressed. E-mail: tmcahill@ucdavis.edu.
2001, 3, 306-310.
(
(
1) CICAD. WHO, 2002.
2) U.S. Public Health Service In Agency for Toxic Substances and Disease Registry
(26) Huynh, C. K.; Vu-Duc, T. Anal. Bioanal. Chem. 2002, 372, 654-657.
(27) Dong, J. Z.; Moldoveanu, S. C. J. Chromatogr., A 2004, 1027, 25-35.
(28) Weisel, C. P.; Zhang, J. F.; Turpin, B. J.; Morandi, M. T.; Colome, S.; Stock,
T. H.; Spektor, D. M.; Korn, L.; Winer, A.; Alimokhtari, S.; Kwon, J.; Mohan,
K.; Harrington, R.; Giovanetti, R.; Cui, W.; Afshar, M.; Maberti, S.; Shendell,
D. J. Exposure Anal. Environ. Epidemiol. 2005, 15, 123-137.
(ATSDR); U.S. Public Health Service, USPHS, 1990.
(
(
3) OEHHA. Chronic Toxicity Summary, Acrolein; 2000; Batch 2A.
4) Ghilarducci, D. P.; Tjeerdema, R. S. Rev. Environ. Contam. Toxicol. 1995,
1
44, 95-146.
1
0.1021/ac051947s CCC: $33.50 © 2006 American Chemical Society
Analytical Chemistry, Vol. 78, No. 7, April 1, 2006 2405
Published on Web 02/28/2006

separation of complex carbonyl mixtures typically found in
1
5,26,29,30
air.
Since these problems can cause positive and negative
biases, acrolein concentrations reported in the literature are
variable and the precise values remain controversial. In addition,
the long sampling times necessary when using cartridges, typically
-1
4
-12 h using flow rates of 0.1-1.0 L‚min , make them unsuitable
for measuring short-term fluctuations and exposures. A rigorous
multilaboratory study comparing various methods found the
24
DNPH method unsuitable for acrolein. Progress has been made
in resolving these limitations, such as using mass spectrometry
instead of UV detection, but the instability of the DNPH-acrolein
hydrazone under the conditions necessary for collection from air
(
acidified DNPH cartridge over 1-4 h) has not been overcome.
31
OSHA method 52 employs an XAD-2 adsorbent cartridge coated
with 2-(hydroxymethyl)piperidine; however the method sensitivity
of 3 ppb for an 8-h sample at 0.1 L‚min- is not sufficient for
ambient acrolein measurements. Dansylhydrazine (DNSH) and
1
4
-hydrazinobenzoic acid have been used to trap carbonyls in
cartridges and passive samplers but have not yet provided
9
,10,32
reproducible values for ambient acrolein levels.
The use of
other carbonyl derivatizing agents, including pentafluorophenyl-
hydrazine, o-benzylhydroxylamine, n-benzylethanolamine, cys-
teamine, and n-methyl-4-hydrazino-7-nitrobenzofurazan, has met
with limited success due to the need for expensive equipment or
reagents, inadequate sensitivity, or poor selectivity.25,30,33-35
The objective of this research was to develop and validate an
analytical procedure capable of detecting acrolein and other
gaseous carbonyls at low part-per-trillion concentrations with short
Figure 1. Schematic diagram for the mist chamber used for air
sampling. The all-glass chambers can be stacked in series to
determine collection efficiency and will allow air flow rates of up to
-
1
20 L‚min .
(
10 min) sample collection times. The new method employs a mist
chamber, also called a Cofer scrubber, containing a sodium
bisulfite solution that traps carbonyls from the air by forming
stable, water-soluble sulfonates.
dissociated and the free carbonyls derivatized with o-(2,3,4,5,6-
pentafluorobenzyl)hydroxylamine (PFBHA), forming thermally
stable oxime adducts that can be analyzed by gas chromatogra-
phy/electron capture negative ionization mass spectrometry (GC/
4
using labeled acrolein (acrolein-d ) as a matrix spike (field positive
control) prior to sample collection. The sensitivity and precision
of the new methodology were then determined under field
conditions to give the most representative estimates of method
performance.
3
6-42
The sulfonates are then
EXPERIMENTAL METHODS
3
3,43,44
Reagents. Capillary GC/GC/MS grade methanol and hexane
ECNI MS).
The potential for positive and negative artifacts
were acquired from Burdick & Jackson (Muskegon, MI). HPLC
grade water and sodium sulfite were purchased from Fisher
Scientific (Fairlawn, NJ). Carbonyl standards (acrolein, methac-
rolein, methyl vinyl ketone, crotonaldehyde, glyoxal, methyl
arising from ozone and atmospheric precursors, such as isoprene
and 1,3-butadiene, was evaluated in the analytical system. The
method was then validated in both the laboratory and in the field
(
29) Dabek-Zlotorzynska, E.; Lai, E. P. C. J. Chromatogr., A 1999, 853, 487-
96.
glyoxal, benzaldehyde, benzaldehyde-d
6
), PFBHA, and hydrogen
4
peroxide (30%) were purchased from Sigma/Aldrich (St. Louis,
MO). Labeled acrolein (acrolein-d ) was synthesized by Cam-
4
bridge Isotopes (Andover, MA).
(
(
30) Otson, R.; Fellin, P.; Tran, Q.; Stoyanoff, R. Analyst 1993, 118, 1253-1259.
31) U.S. Department of Labor, O.S.H.A., 1989, http://www.osha.gov/dts/sltc/
methods/organic/org052/org052.html.
(
32) Zhang, I.; Zhang, L.; Fan, Z.; Ilacqua, V. Environ. Sci. Technol. 2000, 34,
Standard solutions (10 ng/µL in methanol) were prepared for
the carbonyls and two labeled compounds (acrolein-d , benzalde-
hyde-d ). A mixture of the labeled carbonyls was prepared (10
2
601-2607.
(
(
(
(
(
(
33) Ho, S. S. H.; Yu, J. Z. Environ. Sci. Technol. 2004, 38, 862-870.
34) Jain, V. D. T. J. Chromatogr., A 1995, 709, 387-392.
35) Yasuhara, A.; T. Shibamoto J. Chromatogr., A 1994, 672, 261-266.
36) Betterton, E. A.; Hoffmann, M. R. J. Phys. Chem. 1987, 91, 3011-3020.
37) Boyce, S. D.; Hoffmann, M. R. J. Phys. Chem. 1984, 88, 4740-4746.
38) Dufour, J. P.; Leus, M.; Baxter, A. J.; Hayman, A. R. J. Am. Soc. Brew. Chem.
4
6
ng/µL of each) for use as a matrix spike. The PFBHA stock
solution was 50 mM (12.5 mg/mL in methanol). The aqueous
0
.1 M sodium bisulfite was prepared by mixing 12.6 g of sodium
sulfite in 1000 mL of water, adjusting the pH to 5.0 with 1.0 M
SO , and allowing the solution equilibrate for 7 days sealed at
1
999, 57, 138-144.
39) Kaneda, H.; Osawa, T.; Koshino, S. J. Agric. Food Chem. 1994, 42, 2428-
432.
40) Kok, G. L.; Gitlin, S. N.; Lazrus, A. L. J. Geophys. Res.-Atmos. 1986, 91,
801-2804.
(
(
2
H
2
4
room temperature.
2
Collection and Derivatization. Carbonyls were collected by
drawing air through a glass mist chamber (Figure 1) containing
a sodium bisulfite solution. The mist chamber is clamped to a
ring stand in an upright position with a vacuum tube, connected
to a small pump, attached to the top. The air enters the mist
(
(
(
41) Lowinsohn, D.; Bertotti, M. J. Chem. Educ. 2002, 79, 103-105.
42) Olson, T. M.; Hoffmann, M. R. J. Phys. Chem. 1988, 92, 533-540.
43) Yu, J. Z.; Jeffries, H. E.; Lelacheur, R. M. Environ. Sci. Technol. 1995, 29,
1
923-1932.
44) Yu, J. Z.; Jeffries, H. E.; Sexton, K. G. Atmos. Environ. 1997, 31, 2261-
280.
(
2
2406 Analytical Chemistry, Vol. 78, No. 7, April 1, 2006

chamber through a small orifice at the bottom, which opens to a
glass tube. This tube surrounds a smaller tube connected to the
bisulfite reservoir below. The air flow creates a negative pressure
differential that draws the bisulfite solution up into the air stream.
The result is a fine mist, which provides sufficient contact between
carbonyls in the air and bisulfite ions to ensure adduct formation.
A baffle in the top of the chamber keeps >95% of the mist within
chamber containing an aqueous PFBHA solution.45 Since the
reactions of PFBHA with carbonyls are relatively slow (2-24 h),
more volatile compounds with Henry’s law constants less than
103 M‚atm were not retained. The use of bisulfite instead of
water/PFBHA in the mist chamber allowed more volatile species,
including acrolein, to be trapped by forming water-soluble sulfonic
-
1
acid adducts with the carbonyls. The solution was adjusted to a
-
1
-
the chamber during a 10-min sampling period at 20 L‚min . An
average of 9.7 ( 0.21 mL of solution was retained from an initial
volume of 10.0 mL in a single mist chamber (n ) 10). Since two
mist chambers are connected in series, any losses from the first
chamber will enter the second chamber. A 3-µm Teflon filter is
placed between the second mist chamber and vacuum source to
block any mist droplets from escaping the system. Each mist
chamber has a characteristic maximum flow rate, ranging from
pH of 5.0 since the bisulfite ion (HSO
3
) concentration is greatest
at this pH. The reversible formation of the monosulfonate occurs
rapidly on the order of seconds to minutes. Bisulfite will also add
irreversibly to the double bond in unsaturated compounds, but
this is a much slower reaction that only becomes important (>10%
disulfonate formation) after 24 h:38
-1
1
2 to 25 L‚min , based on the orifice size, geometry, and vacuum
strength. When used in series, each pair of mist chambers also
has a characteristic maximum flow rate that ranges from 10 to 22
-1
L‚min . These rates were determined for all mist chambers, both
singly and in pairs, using a calibrated DryCal Lite Primary flow
meter (Bios International Corp., Butler, NJ), eliminating the need
for a flow controller in the field.
After sample collection, hydrogen peroxide (1.04 mmol, a slight
stoichiometric excess compared to bisulfite) was added to the
collection solution to remove free bisulfite, and then PFBHA (1
mM final concentration) was added to the solution. The solution
The stability of the carbonyl-bisulfite adducts was measured
over a period of 30 days to determine the maximum acceptable
time interval between sample collection and derivatization.
PFBHA Derivatization. The optimum conditions for the
carbonyl derivatization with PFBHA were determined for six
aldehydes and ketones: acrolein, methacrolein, methyl vinyl
ketone, crotonaldehyde, glyoxal, and methyl glyoxal. Since the
presence of bisulfite severely inhibited the PFBHA derivatization
of the carbonyls, hydrogen peroxide was added to oxidize the free
bisulfite to sulfate. Four different molar ratios of peroxide to
bisulfite were evaluated to determine the optimum peroxide
concentration. In addition, the carbonyls were also mixed with
peroxide (1.04 and 2.08 mmol) in the absence of bisulfite to ensure
that carbonyls would not be oxidized. Last, peroxide was added
to a vial containing bisulfite, isoprene, and 1,3-butadiene at concen-
trations that were 1000-fold greater than normally expected in the
environment to ensure that peroxide did not oxidize these
precursor compounds into carbonyls, thus creating positive
artifacts in the sampling system.
2 4
was acidified with 0.2 mL of 18 M H SO to encourage dissociation
of the carbonyl-bisulfite adducts and to ionize excess PFBHA
and allowed to react at room temperature for 24-96 h. The
PFBHA derivatives were then extracted twice with 5 mL of hexane,
dried over sodium sulfate, and the volume reduced to 0.5 mL with
nitrogen evaporation. An injection standard consisting of PFBHA-
6
derivatized acetone-d was added to the samples prior to analysis.
Instrumental Analysis. The analysis of the PFBHA-carbonyl
oximes was conducted using an Agilent 6890N gas chromatograph
coupled to a 5793N quadrupole mass spectrometer. A 30-m DB-
XLB capillary column was used for separating the derivatives (0.25-
mm i.d., 0.25-µm film thickness; J&W Scientific, Folsom, CA). The
initial oven temperature was set to 50 °C, which was held for 2
min and then ramped at 5 °C/min to 150 °C, 20 °C/min to 260
The second parameter optimized was the concentration of
PFBHA used for derivatization. Four different PFBHA concentra-
tions were evaluated for their ability to derivatize carbonyls in a
°
C, 30 °C/min to 325 °C, and held for 5 min. The detector was
operated in the negative chemical ionization mode (m/z ) 50-
00), which affords the highest sensitivity with fluorinated
0
.1 M bisulfite solution over 24 h with a slight molar excess of
peroxide.
The last derivatization parameter optimized was the derivati-
5
compounds. The source temperature was constant at 150 °C, and
the reagent gas was methane (40%).
zation time. Four sets of samples (n ) 3 for each condition) were
prepared in a 0.1 M bisulfite solution with a slight molar excess
of peroxide and were derivatized for 1, 2, 4, and 7 days.
Total ion chromatograms were used for both characterization
and quantification. Quantification was performed using charac-
teristic ions that occur in the ECNI mass spectra of PFBHA-
oximes. Most aldehydes and ketones, including acrolein, lose an
Mist Chamber Collection Efficiency. The collection ef-
ficiency (CE) of the bisulfite solution in the mist chamber was
initially determined in the laboratory for the six carbonyls using
-
3
HF fragment and have a unique, characteristic ion at [M - 20] .
a Tedlar bag containing ∼1 µg/m of each compound. The bag
-1
For dicarbonyls and hydroxycarbonyls, the characteristic ions are
was filled by passing 200 L of zero grade air at 5 L/min through
a U-tube wrapped with heating tape and containing 200 ng of each
carbonyl in methanol. The U-tube was held at room temperature
(21 °C) for 5 min and gradually heated to 100 °C over the next 30
min. The contents of the bag were then drawn through two mist
chambers in series, each containing 10 mL of 0.1 M bisulfite
solution and 10 µL of the labeled matrix spike, at a rate of 20
-
-
[
M - 181] and [M - 51] , respectively. A number of common
pentafluorobenzyl-oxime fragments (m/z ) 178, 181, 196, 197)
are also present and can be used to quickly identify the presence
of an aldehyde or ketone functional group.
Carbonyl-Bisulfite Adduct Formation. Previous studies
demonstrated that water-soluble, nonvolatile compounds such as
glyoxal and methyl glyoxal were effectively trapped in a mist
-1
L‚min for 10 min. The resultant concentrations of the carbonyls
Analytical Chemistry, Vol. 78, No. 7, April 1, 2006 2407

were determined in each mist chamber and the collection
efficiency was calculated by
The last site was Roseville, a suburban city impacted by a major
railroad depot and high motor vehicle traffic, located 15 miles
northeast and normally downwind of Sacramento. Meteorological
conditions for the three sites were seasonally typical during sample
collection. Two or three sets of samplers, each of which consisted
of two mist chambers in series, were used to collect air between
CE ) 1 - [B]/[A]
(1)
where [A] and [B] are the concentrations of a specific compound
in mist chambers A and B, respectively. It is important to note
that this formula for CE assumes that each mist chamber removes
a fixed fraction of the analyte from the incoming air, regardless
of the concentration.
1
2
1 a.m. and 2 p.m. on separate days in August and September
005. Ten minutes prior to collection, the mist chamber solutions
(
1
10 mL of 0.1 M bisulfite for each chamber) were spiked with
00 ng of acrolein-d and benzaldehyde-d . The air was then drawn
through the mist chambers for 10 min using a vacuum pump
VP0660, Medo) using either line power (Roseville) or a heavy-
4
6
Ozone/Precursor Interferences. The presence of ozone and
common atmospheric precursors, such as 1,3-butadiene and
isoprene, are potential sources of positive and negative artifacts
(
duty deep-cycle battery with a power inverter (Salt Point, Lassen).
The air flow for each set of mist chambers was determined prior
to each sampling event as described earlier using identical pumps
and power supplies. The flow rates for the mist chamber sets
46,47
when sampling for carbonyls in air.
Positive artifacts can occur
when ozone oxidizes precursor species present to produce
carbonyls, thus creating artificially high concentrations of the
carbonyls. Negative artifacts arise from the direct oxidation of
carbonyls by ozone, resulting in lower concentrations than are
actually present. The use of an ozone scrubber, which is necessary
in methods using hydrazine derivatizing agents (DNPH, DNSH),
not only increases the cost but may also affect the collection of
-
1
ranged from 13 to 19 L‚min . After the 10-min sampling period,
each mist chamber solution was emptied into separate 50-mL glass
screw-cap test tubes (“reaction” tubes) containing 100 µL of 30%
hydrogen peroxide, 200 µL of 50 mM PFBHA, 1 mL of 1.8 M
2 4
H SO , and 2.5 mL of hexane. The mist chambers were then rinsed
1
2,48,49
the sample.
twice with 3 mL of HPLC grade water and the rinses added to
the reaction tubes, which were capped, gently shaken, and stored
upright in a closed box at ambient temperature. Two field blanks
were prepared at each site using the same process, including
adding the collection solution to the mist chambers, but the
vacuum pumps were not running so no air flowed through the
chambers. Two reagent blanks were prepared at each site by
adding 10 µL of labeled matrix spike to 10 mL of bisulfite solution,
waiting 10 min, and transferring the solution to a reaction tube,
which was subsequently handled and stored in the same manner
as the samples. A six-point calibration curve was prepared in the
field during each sampling event using ampules containing 0, 1.25,
5.0, 25.0, 50.0, and 125.0 ng of the carbonyl standards in 0.5 mL
of methanol. The contents of each ampule were added to separate
vials containing 10 mL of 0.1 M sodium bisulfite, which were then
spiked with the labeled matrix spike, allowed to react for 10 min,
and added to reaction tubes in the same manner as the samples
and blanks. The calibration curve was stored with the samples;
thus, it was exposed to the same conditions and time period as
the samples.
The effects of ozone and atmospheric precursors (1,3-butadiene
and isoprene) on the bisulfite/mist chamber system were evalu-
ated by passing 200 L of zero grade air or ozonated air (100 ppb)
through a mist chamber containing 10 mL of 0.1 M bisulfite
(
blank), bisulfite + carbonyls (250 ng of each carbonyl), or
3
-1
bisulfite + precursors (500 µg/m ) at a rate of 20 L‚min (n ) 3
for each condition). Isoprene and 1,3-butadiene were chosen as
precursors since they are considered to be the most abundant
naturally emitted and anthropogenic substances that react in the
atmosphere to produce carbonyl species, including acrolein,
methacrolein, and methyl vinyl ketone. Labeled acrolein and
benzaldehyde were added to the mist chamber collection solution
prior to each test. Ozone was added to the air using an ozone
generator (Jelight model 600), and the ozone concentration was
monitored continuously using an in-line ozone monitor (Dasibi
model 1008-AH).
Field Testing/Method Validation. The method was field-
tested by determining atmospheric carbonyl concentrations in
three locations. The first was Salt Point, which represented clean
marine-boundary layer air on the northern California coast with
no terrestrial sources of carbonyls. The second site was Juniper
Lake in Lassen Volcanic National Park, a remote coniferous forest
area in northern California that served as the control site with
biogenic sources but little or no anthropogenic influence. Long-
term aerosol records indicate that Lassen Volcanic National Park
is one of the cleanest areas in the 48 contiguous United States.50
The samples, blanks, and calibration curve were allowed to
react for 96 h, after which they were shaken for 30 s, the hexane
layer was removed, and the samples were re-extracted twice with
2
.5 mL of hexane. The hexane extracts were passed through a
glass column containing anhydrous sodium sulfate to remove any
residual water, and each extract was reduced to a volume of 0.5
mL under nitrogen evaporation. The extract concentrates were
then analyzed by GC/ECNI MS. Collection efficiencies and
atmospheric concentrations were determined for acrolein and
(
(
(
(
(
(
45) Spaulding, R. S.; Talbot, R. W.; Charles, M. J. Environ. Sci. Technol. 2002,
6, 1798-1808.
46) Grosjean, D.; Grosjean, E.; Williams, E. L. Environ. Sci. Technol. 1994, 28,
86-196.
47) Grosjean, D.; Williams, E. L.; Grosjean, E. Environ. Sci. Technol. 1993, 27,
30-840.
48) Rodler, D. R.; Nondek, L.; Birks, J. W. Environ. Sci. Technol. 1993, 27,
814-2820.
3
1
selected aldehydes and ketones using acrolein-d
standard for the unsaturated compounds and benzaldehyde-d
4
as the internal
as
8
6
the internal standard for benzaldehyde and the dicarbonyls. The
minimum detectable limit (MDL) was calculated by taking the
average field blank plus 3 standard deviations of the field blanks
for each site.
2
49) Kleindienst, T. E.; Corse, E. W.; Blanchard, F. T.; Lonneman, W. A. Environ.
Sci. Technol. 1998, 32, 124-130.
50) Malm, W. C.; Sisler, J. F.; Huffman, D.; Eldred, R. A.; Cahill, T.A. J. Geophys.
Res.-Atmos. 1994, 99, 1347-1370.
2408 Analytical Chemistry, Vol. 78, No. 7, April 1, 2006

Figure 2. Loss (expressed as the natural logarithm of the change
of concentration) of acrolein, crotonaldehyde, methyl glyoxal, and
methyl vinyl ketone as a function of storage time in a 0.1 M bisulfite
solution (n ) 3). The samples were stored at room temperature in
the dark. The results show that unsaturated compounds eventually
react irreversibly with bisulfite, but the reaction with methyl vinyl ketone
occurs much faster. Methyl glyoxal, a saturated dicarbonyl, showed
no decline in response during 30 days. The calculated half-lives of
methyl vinyl ketone, methacrolein, crotonaldehyde and acrolein were
Figure 4. Effect of PFBHA concentration on carbonyl derivatization
yield for a 24-h reaction period (n ) 3). Concentrations of PFBHA
greater than 1 mM provided no statistically significant increases in
derivatization yield (t-test, p > 0.05 for all compounds).
1.1, 12.3, 12.5, and 13.6 days, respectively.
Figure 5. PFBHA derivatization reaction kinetics (n ) 3). The
PFBHA derivatization of the unsaturated, monocarbonyls was com-
plete after 24 h and gradually declined over the next 6 days. The
saturated dicarbonyls (glyoxal and methyl glyoxal) required 2-4 days
for maximum derivatization due to the need for both carbonyls to be
derivatized.
Figure 3. Influence of peroxide concentration on the PFBHA
derivatization of acrolein in water, bisulfite, and hydrogen peroxide/
bisulfite solutions (n ) 3). The presence of bisulfite caused a >90%
reduction in the aqueous PFBHA derivatization yield. The addition of
hydrogen peroxide (1.04:1 or 2.08:1 molar ratio of peroxide to bisulfite)
resulted in derivatization yields 90-95% of the aqueous yield. Higher
peroxide concentrations resulted in lower yields.
(Figure 3) showed that a slight molar excess of peroxide to
bisulfite (1.04:1) resulted in maximum derivatization. Molar ratios
of 5:1 (peroxide/bisulfite) or more had negative effects on the
analyte response, presumably through oxidation of the derivatized
analytes or interference with the PFBHA derivatization reaction.
The free carbonyls were unaffected by the lower concentration
of peroxide since carbonyls added to the peroxide solution (not
shown) gave the same responses as carbonyls in water. The
addition of the precursor compounds of 1,3-butadiene and isoprene
to the peroxide solution did not generate detectable carbonyl
formation even at concentrations that were 1000-fold higher than
expected in the environment.
The minimum concentration of PFBHA required for maximum
derivatization yield was determined to be 1 mM (Figure 4). Lower
concentrations were less efficient in derivatizing the dicarbonyl
species, while higher concentrations yielded no statistically
significant increases in derivatization (t-test, p > 0.05 for all
compounds) and gave larger reagent peaks in the chromatograms.
Based on these results and the relatively high cost of PFBHA
($100/g), the 1 mM PFBHA solution was determined to be the
optimum concentration.
RESULTS AND DISCUSSION
Carbonyl-Bisulfite Adduct Formation. The adducts of the
unsaturated compounds declined over the 30 days of storage
(Figure 2), which was most likely due to the irreversible formation
of disulfonates. The stability of the acrolein, methacrolein, and
crotonaldehyde adducts were similar (t1/2 ∼ 12.5 days) while the
methyl vinyl ketone adducts disappeared rapidly (t1/2 ∼ 1.1 days).
The adducts of the saturated dicarbonyls, methyl glyoxal and
glyoxal, showed no losses over the 30-day period. To provide
consistency and to reduce potential loses of the unsaturated
species, presumably through disulfonate adduct formation, future
samples were derivatized in the field immediately upon sample
collection.
PFBHA Derivatization. The optimal derivatization conditions
were determined by testing different reagent concentrations and
reaction times. The results from the peroxide optimization test
Analytical Chemistry, Vol. 78, No. 7, April 1, 2006 2409

Table 1. Mist Chamber Collection Efficiencies (CE) for
Selected Carbonyls under Laboratory and Field
Conditionsa
Tedlar bag
Lassen
Roseville
carbonyl
acrolein
methacrolein
methyl vinyl ketone
crotonaldehyde
glyoxal
methylglyoxal
benzaldehyde
(n ) 3)
(n ) 9)
(n ) 6)
0.85 ( 0.04
0.82 ( 0.10
0.65 ( 0.06
0.94
0.86 ( 0.11
0.89 ( 0.05
n/a
0.72 ( 0.06
< MQL
< MQL
0.79 ( 0.06
1.0 ( 0.12
0.76 ( 0.10
1.0 ( 0.17
0.70 ( 0.07
< MQL
0.67 ( 0.06
0.70 ( 0.15
< MQL
0.71 ( 0.06
0.82 ( 0.08
a
If one or both mist chamber concentrations were below the
minimum quantification level (< MQL), then the CE could not be
determined. Collection efficiencies are not presented for Salt Point since
the compounds were below the minimum quantifiable limit in the
second mist chamber.
Figure 6. Effect of bisulfite concentration on collection efficiency
n ) 3). Collection efficiencies of the unsaturated carbonyls were
(
minimal in water and increased with increasing bisulfite concentration.
The collection efficiencies of the saturated dicarbonyls, glyoxal and
methyl glyoxal, were independent of the bisulfite concentration.
The derivatization reaction was complete within 48-168 h,
depending on the carbonyl species (Figure 5). There was no
derivatization time that was ideal for all compounds since the
unsaturated carbonyls were completely derivatized after 24 h while
the dicarbonyls of glyoxal and methyl glyoxal required up to 7
days for complete derivatization. The dicarbonyls likely required
longer reaction times since two carbonyl groups must be deriva-
tized for these compounds. The unsaturated carbonyl abundances
declined during a seven-day derivatization, possibly due to bisulfite
addition to the double bond or reactions with residual peroxide.
Due to the variable reaction time of the carbonyls, a calibration
curve should be derivatized at the same time as the samples when
quantifying carbonyls other than acrolein or benzaldehyde. The
use of deuterated acrolein and benzaldehyde as internal standards
accounts for any variations in derivatization yield for these
compounds. Once the derivatives have been extracted and stored
in anhydrous hexane, they appear to be stable for extended
periods of time. No losses were observed when a mixture of
derivatized and extracted acrolein (200 pg/µL) was stored at 4
Figure 7. Effect of ozone and atmospheric precursors on mist
chamber carbonyls (n ) 3). There were no differences in mist
chamber carbonyl concentrations when either zero grade air or
ozonated air (100 ppb) was passed through mist chambers containing
bisulfite only (blank), bisulfite + 136 µg of isoprene and 100 µg of
1,3-butadiene (precursors), and bisulfite + 250 ng of carbonyls
(carbonyls).
°
C and analyzed twice monthly for 6 months (average 200 ( 14,
carbonyls were considerably lower. During the 0.1 M bisulfite tests
n ) 3), we recovered an average of 186 ( 31 ng of acrolein
relative standard deviation (RSD) ) 7.0%, n ) 12).
(
Collection Efficiency. The CE of the mist chamber was
evaluated for water and four different bisulfite concentrations. The
results showed that a bisulfite concentration of 0.1 M was
necessary for maximum trapping of acrolein and other unsaturated
aldehydes in the mist chamber (Figure 6). Presumably, the higher
concentration of bisulfite results in more rapid adduct formation,
which makes the carbonyls effectively nonvolatile and more likely
to be retained in the collection solution. As expected, the CEs of
the less volatile compounds, glyoxal and methyl glyoxal, were
independent of the bisulfite concentration, since they were
effectively collected in an aqueous PFBHA solution. With the
exception of methyl vinyl ketone (CE ) 0.65), the CEs for all the
compounds using 0.1 M bisulfite were greater than 0.80 (Table
between both mist chambers, which corresponds to 93 ( 16% of
the enrichment amount of 200 ng. This recovery value agrees well
with the predicted collection efficiency for two mist chambers in
series.
Ozone and Atmospheric Precursors. The resistance of the
sampling system to ozone was demonstrated by passing zero
grade air and ozonated air (100 ppb) through mist chambers
containing bisulfite only (blank), bisulfite + precursors, and
bisulfite + carbonyls. There were no carbonyls generated in the
bisulfite-only or the bisulfite + precursor chambers, thus dem-
onstrating that ozone produced no positive artifacts from interac-
tions with precursor compounds. In addition, no apparent differ-
ences were seen between using zero grade air or ozonated air in
the chambers containing carbonyls, thus showing that ozone did
not degrade the carbonyls present in solution during sample
collection (Figure 7).
1). When two mist chambers are placed in series, 96% of a carbonyl
with a CE of 0.8 can be collected since 80% of the carbonyl is
trapped in the first mist chamber and 80% of the remaining 20%
(or 16%) is trapped in the second chamber. The collection
efficiencies for the field samples were comparable to those
obtained in the laboratory, even though the concentrations of the
The bisulfite/mist chamber system is inherently resistant to
interferences from ozone for two reasons: (1) bisulfite is rapidly
2410 Analytical Chemistry, Vol. 78, No. 7, April 1, 2006

Table 2. Selected Carbonyl Concentrations and Minimum Detection Levels (MDLs) in Ambient Air from Pristine and
a
Urban Areas
MDL
Salt Point
Lassen
Roseville
carbonyl
acrolein
methacrolein
methyl vinyl ketone
crotonaldehyde
glyoxal
methylglyoxal
benzaldehyde
(range)
(n ) 6)
(n ) 9)
(n ) 6)
0.012-0.035
0.007-0.033
0.038-0.050
0.009-0.048
0.050-0.216
0.029-0.038
0.020-0.044
0.056 ( 0.011
<0.027
0.089 ( 0.013
0.048 ( 0.013
0.105 ( 0.050
0.112 ( 0.025
<0.091
0.047 ( 0.018
<0.044
0.290 ( 0.022
0.044 ( 0.012
0.103 ( 0.026
0.019 ( 0.002
0.340 ( 0.088
0.252 ( 0.013
0.233 ( 0.077
<0.038
<0.021
<0.050
<0.038
0.026 ( 0.007
a
3
Units are µg/m . Values below the MDL for a specific site are listed as “<” the MDL for that site.
oxidized by ozone to form sulfate,51 thus the high concentration
of bisulfite quenches any ozone present and protects the trace
quantities of the collected carbonyls, and (2) the gas-phase
oxidation of acrolein and related unsaturated aldehydes by ozone
is relatively slow (t1/2 ) 3 h) and thus would not occur to a
great extent in a 10-min sampling period even if ozone were
present.
highest level of quality control, since any losses in the samples
during collection, transport, storage, and processing were reflected
by the surrogates. Recoveries for the labeled surrogates were 86
4 6
( 10.2% for acrolein-d and 92 ( 4.5% for benzaldehyde-d ,
5
2
reflecting the established collection efficiencies for these com-
pounds. In addition, the calibration curves were prepared in the
field at the same time and under the same conditions as the
sample collection; therefore, any environmental influences would
affect the samples and calibration curves in the same manner. To
our knowledge, this is the first time that these rigorous controls
have been used in the collection and measurement of acrolein in
air.
Field Testing/Method Validation. The optimized method
was tested on three separate occasions to verify collection
efficiency data obtained in the labortory and to determine the
method sensitivity and precision in the field. The locations were
chosen to represent hemispheric background conditions (Salt
Point), a remote, biogenic-dominated area (Lassen), and a high-
density suburban setting with known sources (Roseville). The
results (Table 2) showed a low hemispheric background concen-
The EPA has established a chronic reference concentration
3
(RfC) for acrolein of 0.02 µg/m , a value based on subchronic
animal studies performed in 1985.53 The lowest exposure concen-
3
3
tration of acrolein (0.056 µg/m ) and benzaldehyde (0.026 µg/
tration used in these studies was 0.4 ppm or 1 mg/m , which was
3
m ) at Salt Point, with all other compounds falling below the
also the lowest level at which adverse effects were observed. A
series of uncertainty factors was then applied to obtain the
detection limit. The biogenic sources of acrolein appeared to be
3
3
limited since the concentrations at Lassen (0.089 µg/m ) were
reference level of 0.02 µg/m . The sensitivity of the method
only slightly higher than at Salt Point. The only carbonyl measured
that appeared to have a strong biogenic source was crotonalde-
described allowed us to determine ambient acrolein concentrations
in remote areas on the Pacific Coast and near Mt. Lassen that
have no known anthropogenic sources of acrolein. The concentra-
tions at both of these sites were more than twice the EPA RfC,
and the levels in suburban Roseville were more than 10 times
the RfC. In light of this information, it would seem prudent to
reevaluate the effects of chronic exposure to these lower levels
of acrolein.
hyde, which had concentrations 5-10 times higher at Lassen
3
(
0.112 µg/m ) than either Salt Point or Roseville. The effects of
urban enrichment were apparent for the other compounds with
3
acrolein concentrations averaging 0.29 µg/m , nearly five times
the concentrations measured at Salt Point. The MDL for acrolein
3
3
ranged from 0.012 µg/m at Lassen to 0.035 µg/m at Roseville,
due to higher field blanks at the latter site.
The method precision for Salt Point and Lassen was deter-
mined by calculating the RSD of all samples at each site, since
there were no significant differences between the sets of samples
taken ∼30 min apart. There were, however, noticeable temporal
variations in the acrolein values for the two sets of triplicate
CONCLUDING COMMENTS AND DIRECTIONS FOR
FUTURE WORK
The method described herein for the collection and measure-
ment of carbonyls in air offers strict quality controls, a short
sampling time, and a very high sensitivity not found in established
methods. The ability to detect even minor fluctuations of acrolein
levels over a short time period is a unique and powerful aspect of
this method. This high time resolution is necessary for measuring
temporal variations due to fluctuating point sources, such as traffic
emissions. The values obtained for hemispheric background,
biogenic background, and urban enrichment demonstrate the
versatility and utility of the method and have not, to our
knowledge, been previously reported by a single investigator using
a consistent methodology and experimental design. The precision
of the method was also good (<20%), even for samples with very
3
samples collected in Roseville (set 1, 0.322 ( 0.027 µg/m ; set 2,
3
0
.258 ( 0.016 µg/m ); thus the RSD was calculated for each set.
The RSD values for acrolein were 19.3 (Salt Point), 14.3 (Lassen),
and 7.6% (Roseville). A RSD of 19% at a hemispheric background
site shows the consistency of the method even at locations with
very low concentrations of acrolein. The sites with higher ambient
concentrations showed increasing precision with increasing ambi-
ent concentrations.
The use of deuterated acrolein and benzaldehyde as surrogates
in the mist chambers, blanks, and calibration curves provided the
(
(
51) Helmig, D. Atmos. Environ. 1997, 31, 3635-3651.
52) Grosjean, E.; Grosjean, D. Int. J. Chem. Kinet. 1998, 30, 21-29.
(53) Kutzman, R. S., P. E.; Schmaeler, M.; Drew, R. T. Toxicology 1985, 34,
139-151.
Analytical Chemistry, Vol. 78, No. 7, April 1, 2006 2411

low concentrations. The method was validated using a representa-
tive mixture of some of the more common volatile carbonyls.
However, the mist chamber methodology has been applied to a
wider range of carbonyls in the past;45 thus the current method
would likely be applicable to a much larger group of aldehydes
and ketones than those presented here.
There are some constraints in the described methodology that
might limit its widespread application. The first is that the method
is relatively labor intensive in the field, making the collection of
large numbers of samples difficult. Second, the mist chambers
used in the method are not commercially available and must be
custom-made. Last, because the method is sensitive to the duration
of derivatization, a calibration curve must be prepared each
sampling day to quantify compounds for which labeled standards
are not available. Thus, the samples and calibration curve are
collected and stored under the same conditions to ensure a similar
derivatization time period.
GC/MS analysis. It is possible that the disulfonates could be
quantified using liquid chromatography-mass spectrometry,
which may offer a method that is not time-sensitive. Also, a simpler
sample collection system resistant to ozone and not hampered
by adduct instability could be created by the use of a bisulfite-
coated cartridge, although it would likely require the longer
sampling times (4-12 h) needed by other cartridge systems.
ACKNOWLEDGMENT
The authors dedicate this paper to the late Dr. M. Judith
Charles, who initiated this project and was the inspiration for its
completion. In addition, we thank Skip Huckaby for his help in
designing and building the mist chambers. This research was
partly supported by a grant from the Health Effects Institute (HEI),
an organization jointly funded by the U.S. EPA and automotive
manufacturers. The contents of this article do not necessarily
reflect the views of HEI or its constituent groups.
One direction for future method development is to take
advantage of the stable disulfonate adducts of unsaturated car-
bonyls that are formed over time in a bisulfite solution. The current
method deliberately avoids the formation of disulfonates since the
reaction is irreversible and the product cannot be derivatized for
Received for review October 31, 2005. Accepted January
30, 2006.
AC051947S
2412 Analytical Chemistry, Vol. 78, No. 7, April 1, 2006