United States
Environmental Protection
Agency
Environmental Sciences Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S3-84-084 Sept. 1984
Project Summary
Analysis and Characterization of
Organic Carbon Compounds in
Atmospheric Paniculate Matter
Henry Freiser and Jarvis L Moyers
A novel macroporous polymer mate-
rial, Shodex, was evaluated as a sta-
tionary phase in liquid chromatography
for the separation of a wide variety of
aliphatic compounds, oxygenates, and
polynuclear aromatic compounds using
a variety of solvents. Fundamental
studies were performed that determined
the chromatographic properties of
Shodex. In addition to the Shodex
evaluation, a reversed phase ion parti-
tion chromatography procedure was
developed by which, through the use of
methylene blue, a highly sensitive meth-
od for determining submicrogram quan-
tities of alcohols was developed. Ana-
lytical methods to measure the organic
and total carbon content of ambient
particulate matter collected on Teflon
and quartz filters were also compared.
Estimation of the soot or light-ab-
sorbing carbon collected on Teflon and
quartz filters by use of light absorption
methods (light transmission and photo-
acoustic) compared favorably with the
combustion procedure used to measure
soot carbon.
This Project Summary was developed
by EPA's Environmental Sciences Re-
search Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering in-
formation at back).
Introduction
The research conducted in this project
was directed toward developing improved
liquid chromatographic methods to sepa-
rate complex mixtures of organic com-
pounds that are present in ambient
particles.
In order to develop an improved chro-
matographic system, solubility parameter
theory, as originally developed by Hilde-
brand, was applied to the characterization
of a new macroporous polymer, Shodex,
made in Japan. Through the use of the
so-called three-dimensional solubility
parameter, the interactions of the solute
and solvent with the stationary phase can
be mathematically defined. Parameters
such as cohesive energy, dispersion
forces, dipole forces, and hydrogen bond-
ing can be determined through liquid-
liquid partitioning with the stationary
phase. In a fundamental sense, the
relative strengths of these solute-solvent
interactions with the stationary phase are
determined by the kinds and magnitude
of the different inter molecular forces. The
polarities of both the solute and solvent
defined by the Hildebrand approach can
be used as a guide to the strengths of
these interactions
In addition to the fundamental liquid
chromatographic stationary phase char-
acterization, studies were conducted to
develop improved methods of measuring
the elemental and organic content of
ambient particles. The carbon fraction of
ambient particulate matter can account
for 10-90% of the fine particle mass.
Historically, extraction and gravimetric
techniques and thermal combustion fol-
lowed by measurement of evolved organic
matter with a flame ionization detector
were used to determine the organic
matter in high-volume samples. These
procedures suffer, however, from lack of
sensitivity and from questions about
what is actually measured The research
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effort described in the Project Report was
directed at providing a reliable, sensitive
method of measuring the organic and
elemental carbon content of particulate
matter collected on quartz or Teflon
filters.
Experimental
Liquid Chromatography
Chromatograms were obtained using a
Spectra-Physics 3500B gradient liquid
chromatograph and a Spectra-Physics
SP8200 UV/visible detector operated at
254 nm. Chromatograms were also ob-
tained using a second chromatograph
assembled from an Altex Model 110A
pump, Valco injector valve, andSchoeffel
SF-770 Spectroflow detector, also oper-
ated at 254 nm.
The columns were prepacked Shawa-
Denko Polymerpak SP500 The column
was packed with porous polystyrene
divinylbenzene polymer beads, approxi-
mately 12-20/ym in diameter. A variety of
mobile phases were used, including a
50:50 mixture of methanol and water,
chloroform, ethanol, and isooctane. The
solutes tested included cumene, pthahc
acid, m-xylene, aniline, phenanthrene,
and pyrene. Solution concentrations
ranged from 10 to 1000 ppm.
Aerosol Carbon Measurements
A Perkin-Elmer Model 240 elemental
analyzer was used for combustion analy-
sis of carbon collected on the quartz or
glass fiber filters Typically, a 2.67-cm2
aliquot of the filter was introduced into
the combustion chamber for analysis.
A micro-extraction apparatus was de-
signed and fabricated to extract the
compounds from the quartz and Teflon
filters The extraction solution was a
mixture of isoproponal andtolune. Blanks
were typically 2-4 jug/cm2.
A micro-oxidation procedure was de-
veloped to measure the organic content
of aerosols collected on Teflon filters The
sample filter was placed into a solution
containing 10-3M NH4CI, K2S2O3, and
10% H3PCu in deionized water The CO2
evolved during the oxidation was analyzed
with an Oceanography Internationa I Corp.
(Model P1R-200) nondispersive infrared
(NDIR) analyzer.
Light transmission measurements
through the filters were made using a
light source, interference filter, and photo-
detector. The light transmission measure-
ments were made prior to and after
collection of aerosols on the filters to
determine the amount of light attenuation
due to the soot particles.
Results
The research conducted as part of this
project evolved several techniques that
can be used to measure the chromato-
graphic properties of porous polymers
and analyze the organic and elemental
content of ambient particles. Specifically,
the key results of these studies are as
follows:
1. We defined the fundamental chro-
matographic parameters that char-
acterize Shodex stationary phase (a
highly efficient chromatographic
packing developed by ShawaDenko,
Inc., Japan and formulated from
divinylbenzene-crosslinked polysty-
rene that is capable of use under a
wide variation of eluent composi-
tion) and applied this information to
improvements in chromatographic
separation for a broad range of
organic compounds.
2. Reversed phase paired ion partition
Chromatography employing a highly
absorbing dye (methylene blue) as
one of the ions was demonstrated
to show not only does it have the
potential to determine aliphatic
anions and cations, but it also
provides a novel, highly sensitive
method for detecting low molecular
weight alcohols. Calibration curves
for samples in the submicrogram
range were linear (rel. std dev.
<2%). Values of capacity factors
were found to be reproducible,
accurate, rapid, and also applicable
to other families of neutral com-
pounds such as the carboxylic acids,
esters, ketones, etc. The column,
once conditioned, could be used
continuously for several weeks
Moreover, the regenerated column
retained its original characteristics.
In addition to column efficiency, the
observed k' values and sensitivities
remained quantitatively the same.
The behavior of the alcohols on the
dye-containing column were attrib-
uted to the formation of a dye-
alcohol complexthat has a higher k1
than does the alcohol itself. Forma-
tion of the complex occurred in a
rapidly reversible equilibrium fash-
ion characterized by equilibrium
constants whose increase with the
distribution ratios of the alcohols
indicated that the same structural
influences were at work in both
processes.
3. The measurement of total carbon in
particulate samples collected on
quartz and glass filters by high
temperature combustion of aliquots
of the sample in oxygen were
evaluated. For these measure-
ments, a commercial CHN analyzer
(Perkin Elmer 230) was used to
measure the carbon on 2.67 cm2 of
a filter sample. This technique can
be used for high-volume or dichot-
omous filter samples and has
proved to be reliable and quite
sensitive.
4. We determined the carbonate and
bicarbonate carbon by acid CO2
evolution and quantitation by a
NDIR gas phase CO2 detector. The
carbonate-bicarbonate concentra-
tion of airborne particulate matter
is generally quite low, however, in
atmospheres containing relatively
large concentrations of basic soil
constituents, the inorganic carbon
can be a significant fraction of the
total carbon present. This technique
is suitable for use with glass, quartz,
and Teflon filter samples (high
volume and low volume).
5. The measurement of "oxidizable
carbon" on Teflon filters using a
wet oxidation procedure was de-
veloped. The method consisted of
hot oxidation of the material with
peroxydisulfunc acid with subse-
quent quantitation of the evolved
C02by NDIR analysis or gaschroma-
tography. This procedure has been
developed specifically for use with
Teflon filters because higher tem-
perature combustion obviously can-
not be used with a carbon matrix
filter. This procedure will not oxi-
dize highly polymeric and "inert"
carbon. However, there are advan-
tages to using this technique over
extraction methods for measuring
the organic content of particulate
matter. First, this method will ap-
parently measure more carbon than
the various extraction methods
reported. Second, blanks for the
wet oxidation procedure are much
smaller and more reproducible than
we have been able to achieve with
extraction of samples.
6. Estimation of absorbing carbon on
Teflon, quartz, or glass filters by use
of light absorption measurements
(both transmission of light and
photo-acoustic detection) was per-
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formed. When used with size segre-
gated samples, this procedure pro-
vided a reasonable estimate of the
soot content of a paniculate sample.
This value and the wet oxidation
measurement described previously
provided a good estimation of the
total carbon on Teflon filters.
Conclusions
1. A procedure to characterize the
liquid chromatographic properties
of a macroporous polymer was
developed; this polymer can be
used in selective solvent extraction
and analysis of a broad range of
organic compounds.
2. A new procedure was developed
based on the peroxydisulf ate oxida-
tion of ambient particulate organic
compounds collected on Teflon or
quartz filters to COj, followed by the
measurement of CC>2 with a NDIR
analyzer. The procedure does not
oxidize all the ambient organic
compounds, but oxidizes principally
the reactive organics that typically
represent 50-70% of organic matter
present in ambient particulate mat-
ter
3. Light transmission measurements
made during the combustion of
ambient carbon particles collected
on quartzfilters showed a decrease
in light transmission (charring of
the organic carbon) during the
combustion process that was used
to measure the organic content of
ambient particulate matter samples.
This charring would tend to cause
an overestimation of the elemental
carbon and an underestimation of
organic carbon.
Henry Freiser and Jarvis L Moyers are with Department of Chemistry, University
of Arizona, Tucson, AZ 85721.
James D. Mulik is the EPA Project Officer (see below).
The complete report, entitled "Analysts and Characterization of Organic Carbon
Compounds in Atmospheric Particulate Matter," (Order No. PB 84-232 636;
Cost: $10.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
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