Although XRF analysis is considered “nondestructive”, we
were concerned that the XRF analysis may cause degradation
or volatilization of organic chemical species on the filter,
thus compromising subsequent analysis of methoxyphenols
in the PM samples. XRF analysis was performed per batch
of 12 filters placed in the XRF spectrometer under vacuum
(0.15 Torr) for 12 h. During the 12-h period, each filter was
subjected to X-ray bombardment for a total of 45 min, with
beam energies of 7.5-55 kV. Filters were stored at -4 °C
prior to and immediately after the XRF analysis. The results
are summarized in Table 6.
Acknowledgments
This work was funded in part by a U.S. EPA cooperative
agreement (CR82717701), the Northwest Center for Particu-
late Air Pollution and Health (U.S. EPA Grant CR827355),
and the National Institute of Occupational Safety and Health
(R03-OH007656).
Literature Cited
(1) Maykut, N. N.; Lewtas, J.; Kim, E.; Larson, T. V. Environ. Sci.
Technol. 2003, 37, 5135-5142.
(2) Poore, M. W. J. Air Waste Manage. Assoc. 2002, 52, 3-4.
(3) Schauer, J. J.; Cass, G. R. Environ. Sci. Technol. 2000, 34, 1821-
1832.
The co-located samples were either both PM2.5 samples
(sites 1-3) or co-located PM10 and PM2.5 samples (sites 4-10).
For sites 4-7, the PM2.5 samples received XRF analysis,
whereas for sites 8-10, it was the PM10 samples that received
XRF analysis. On the basis of our conclusions from Table 5,
co-located PM10 and PM2.5 samples were treated as equivalent
samples for the paired t-test. As shown in Table 6, concen-
trations of vanillin, syringaldehyde, and acetosyringone were
significantly lower in the filter subjected to XRF analysis when
compared to the corresponding co-located sample that was
not subjected to XRF analysis. Levels of coniferylaldehyde
and sinapylaldehyde were also decreased in the XRF treated
samples, and this difference approached statistical signifi-
cance. Similar results were obtained when nonparametric
methods (sign test) were used to analyze the data in Table
6. These observations are in contrast to our recent report
that XRF analysis of ambient PM samples did not affect
subsequent determination of levoglucosan (28). It is possible
that the energy of the X-ray beam causes chemical trans-
formation of the methoxyphenols. Alternatively, the reduction
in methoxyphenol levels we observed following XRF treat-
ment may be due to evaporation of the semivolatile meth-
oxyphenols either from direct heating by the X-ray beam or
during the 12 h the filters are under vacuum inside the XRF
spectrometer. The vacuum inside the XRF spectrometer is
0.15 Torr. In comparison, the pressure drop across the HI10
and HI2.5 used to collect the samples in the present study
was 27 and 29 Torr, respectively, and the pressure drop across
a high-volume sampler (e.g., Chem-vol) may be as high as
100 Torr. Although the pressure drop across typical PM
samplers does not approach the vacuum inside the XRF
spectrometer, it is nevertheless probable that the accuracy
of measurements of particle-bound methoxyphenols that
are collected by typical ambient PM samplers may be
compromised by a significant desorption artifact.
In conclusion, we developed an improved analytical
method that allows for quantitative determination of meth-
oxyphenols in samples of ambient PM, with good recoveries
and low limits of detection. We observed that ambient PM
and PM standard reference materials could cause oxidation
and nitration of methoxyphenols during sample extraction;
however, this degradation could be prevented by using a
solvent additive (triethylamine). The use of deuterium-labeled
authentic standard compounds to monitor methoxyphenol
recovery is a critical feature of this method; our recovery
data demonstrate acceptable reproducibility and precision
for determination of methoxyphenols in environmental
samples collected on PTFE membrane filters. We also
demonstrated that methoxyphenols are present predomi-
nantly in the fine (PM2.5) particle size fraction and that XRF
analysis of samples compromised subsequent measurement
of methoxyphenol levels. Our study underscores the fact that
many methoxyphenols are chemically reactive and exhibit
appreciable volatilitystwo features that could limit the utility
of these chemicals in source attribution studies. Future
studies are called for to measure the atmospheric stability
of the methoxyphenols and to assess the influence of
adsorption and desorption artifacts on measurements of
methoxyphenols.
(4) Brauer, M.; Hisham-Hashim, J. Environ. Sci. Technol. 1998, 32,
404A-407A.
(5) Mott, J. A.; Meyer, P.; Mannino, D.; Redd, S. C.; Smith, E. M.;
Gotway-Crawford, C.; Chase, E. West J. Med. 2002. 176, 157-
162.
(6) Osterman, K.; Brauer, M. In Forest Fires and Regional Haze in
Southeast Asia; Eaton, P., Radojevic, M., Eds.; Nova Science
Publishers: Hauppauge, NY, 2001; Chapter 10.
(7) Smith, T.; Ward, G. Air sampling of the 2000 Montana wildfire
season. Presented at the Air and Waste Management Association
Annual Conference, 2001; Paper 1131.
(8) Ezzati, M.; Kammen, D. M. Environ. Health Perspect. 2001, 109,
481-488.
(9) Smith, K. R. Proc. Natl. Acad. Sci. U.S.A. 2000, 97, 13286-13293.
(10) Leonard, S. S.; Wang, S.; Shi, X.; Jordan, B. S.; Castranova, V.;
Dubick, M. A. Toxicology 2000, 150, 147-157.
(11) Pryor, W. A. Free Radical Biol. Med. 1992, 13, 659-676.
(12) Schauer, J. J.; Kleeman, M. J.; Cass, G. R.; Simoneit, B. R. Environ.
Sci. Technol. 2001, 35, 1716-1728.
(13) Larson, T. V.; Koenig, J. Q. Annu. Rev. Public Health 1994, 15,
133-156.
(14) Hawthorne, S. B.; Krieger, M. S.; Miller, D. J.; Mathiason, M. B.
Environ. Sci. Technol. 1989, 23, 470-475.
(15) Rogge, W. F.; Hildemann, L. M.; Mazurek, M.; Cass, G. R.;
Simoneit, B. R. T. Environ. Sci. Technol. 1998, 32, 13-22.
(16) Fine, P. M.; Cass, G. R.; Simoneit, B. R. Environ. Sci. Technol.
2002, 36, 1442-1451.
(17) Hawthorne, S. B.; Miller, D. J.; Langenfeld, J. J.; Krieger, M. S.
Environ. Sci. Technol. 1992, 26, 2251-2262.
(18) Nolte, C. G.; Schauer, J. J.; Cass, G. R.; Simoneit, B. R. Environ.
Sci. Technol. 2001, 35, 1912-1919.
(19) Kja¨llstrand, J.; Ramnas, O.; Petersson, G. J. Chromatogr., A 1998,
824, 205-210.
(20) Dills, R. L.; Zhu, X.; Kalman, D. A. Environ. Res. 2001, 85, 145-
158.
(21) Coscia, C. J.; Schubert, W. J.; Nord, F. F. J. Org. Chem. 1961, 26,
5085-5091.
(22) Buu-Ho¨ı, N. P.; Se´alles, J., Jr. J. Org. Chem. 1955, 20, 606-609.
(23) Chau, A. S. Y.; Coburn, J. A. J. Assoc. Off. Anal. Chem. 1974, 57,
389-393.
(24) Liu, L. J.; Box, M.; Kalman, D.; Kaufman, J.; Koenig, J.; Larson,
T.; Lumley, T.; Sheppard, L.; Wallace, L. Environ. Health Perspect.
2003, 111, 909-918.
(25) Marple, V. A.; Rubow, K. L.; Turner, W.; Spengler, J. D. J. Air
Pollut. Control Assoc. 1987, 37, 1303-1307.
(26) Allen, R.; Box, M.; Liu, L.-J. S.; Larson, T. J. Air Waste Manage.
Assoc. 2001, 51, 1650-1653.
(27) Fenimore, D. C.; Davis, C. M.; Whitford, J. H.; Harrington, C. A.
Anal. Chem. 1976, 48, 2289-2290.
(28) Simpson, C. D.; Dills, R. L.; Katz, B. S.; Kalman, D. A. J. Air Waste
Manage. Assoc. 2004, 54, 689-694.
(29) Franz, J. E.; Herber, J. F.; Knowles, W. S. J. Org. Chem. 1965, 30,
1488-1491.
(30) Sobolev, I. J. Org. Chem. 1961, 26, 5080-5085.
(31) Brink, D. L.; Bicho, J. G.; Merriman, M. M. Adv. Chem. Ser. 1966,
59, 177-204.
(32) Polcin, J.; Rapson, W. H. Pulp Pap. Can. 1971, 72, T114-T125.
(33) Atkinson, R.; Arey, J. Environ. Health Perspect. 1994, 102 (Suppl
4), 117-126.
(34) Kleeman, M. J.; Schauer, J. J.; Cass, G. R. Environ. Sci. Technol.
1999, 33, 3516-3523.
Received for review August 20, 2004. Revised manuscript
received October 20, 2004. Accepted October 22, 2004.
ES0486871
9
VOL. 39, NO. 2, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 637