United States
Environmental Protection
Agency
Environmental Monitoring Systems
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S4-84-016 Feb. 1984
Project  Summary
                                                                   .>"%i
Survey  of  Direct Analysis
Methods  for  Organic  Compounds
in   Paniculate   Matter

C. A. Alexander, J. R. Hoyland, R. H. Barnes, and J. S. Ogden
  Spark source, secondary ion and direct
probe mass spectroscopy and infrared.
Raman  and  photoacoustic  optical
spectroscopy were evaluated for their
present  and potential  usefulness in
direct (i.e..  without prior concentra-
tion) qualitative and semiquantitative
analysis of aromatic hydrocarbons in
particulate matter. It was found that
spark source and  secondary ion mass
spectroscopy, and Fourier-Transform
infrared,  Raman  and photoacoustic
spectroscopy did not provide sufficient
sensitivity for the determination  of
environmental levels  (low  ppm  by
weight)  of polycyclic aromatic
hydrocarbons in  particulate  matter.
Direct probe thermal desorption mass
spectroscopy was  found to be capable
of  detection  and quantification  of
organic compounds, particularly high
molecular weight species not detected
with the usual  extraction  and  gas
chromatography or gas chromatogra-
phy/mass spectroscopic analysis. The
National Bureau of Standards (NBS)
Standard Reference Material 1648 was
used to evaluate the various techniques.
It is further concluded that the organic
material absorbed  on ambient particu-
late matter may be much more complex
than previously suspected.
  This Project Summary was developed
by  EPA's Environmental Monitoring
Systems Laboratory, Research Triangle
Park, NC, to announce key finding* of
the research project that if fuUy docu-
mented in a separate report ofthftame
title (see Project  Report ordering' In-
formation at back).
Introduction
  Current methodology for analysis of
organic material  in particulate  matter
involves extraction procedures which are
tedious,  time  consuming,  and  may
contaminate  the  sample.  Analytical
techniques normally  employed for
determining the identity and concentra-
tion of extracted species include gas
chromatography (GC), liquid chromatog-
raphy (LC), or GC combined with mass
spectrometric detection (GC/MS). The
utility of GC and  GC/MS techniques is
limited by the low volatility of many of the
organic species  of interest, and the
efficiency of extraction is thermodynami-
cally limited by the relative free energies
of adsorption and solution. Because the
current state-of-the-art of quantitative
analysis is time consuming, costly, and
can yield uncertain or incomplete results,
a study was undrtaken of experimental
methods currently available which might
prove  capable  of  yielding   such
information  without  prior sample
extraction.  There  are several emerging
techniques which  may be used to
determine  organic  compounds in
particulate matter without  extraction,
i.e., direct  methods. The present study
addresses the question of whether these
direct  methods  have  sufficiently low
detection limits (i.e., low ppm by weight)
and quantitative capabilities to be useful
in monitoring applications.
  The objective of this particular program
WM to evaluate  flue  niMJttfait direct
methods and to make recomiti||ktotions
for  further development of ill most
promising  ones.  A direct  method is

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  defined as one  for which  the  sample
  preparation involves no liquid extraction
  or  other  concentration   steps.   The
  techniques which were evaluated were
  (a) temperature-programmed direct
  probe  mass   spectrometry; (b)  spark
  source mass spectrometry; (c) photoa-
  coustic  spectroscopy; (d)  Fourier
  transform  infrared  absorbance   and
  Raman  spectroscopy; and  (e)  Fourier
  transform reflectance spectroscopy.  The
  NBS Standard Reference Material 1648,
  ambient paniculate matter, was used in
  the evaluations. These techniques were
  evaluated for qualitative and semiquanti-
  tative analyses of polynuclear aromatic
  hydrocarbons. Additionally, a  limited
  investigation  was  made  of   the
  applicability  of  secondary  ion  mass
  spectroscopy  (SIMS) to  organic
  compounds adsorbed on the surface of
  particulate samples.
     Fluorescence spectroscopy, which is
  expected to have greater sensitivity than
  the optical techniques covered here,  was
  not evaluated since it was being studied
  in another project.

  Conclusions and
  Recommendations
     The  results  of  this  experimental
  assessment of presently available direct
  analysis techniques show that  only the
  thermal desorption  mass spectrometry
  technique has much chance of being of
  general applicability. The spark source
  MS technique does not work in enough
  cases to be of practical value. Fast atom
  bombardment and molecular secondary
  ion mass spectrometry are both sensitive
  but  are  not  always  effective  for
  particulate  samples  because  the
  polycyclic  aromatic  material   in  the
       particulate  sample  is  not  readily
       accessible at the surface exposed to the
       ion beam. The optical techniques studied
       suffer from the same problem since the
       organic compounds have selected ener-
       getically favorable sites in the particulate
       phase, and these sites can  be optically
       shielded  from  the  probing radiation.
       Therefore the thermal desorption mass
       spectrometry technique is the most likely
       candidate for successful direct analysis of
       organic compounds in particulate matter.
       This  technique  can  yield quantitative
       data.  Results  obtained on the National
       Bureau   of   Standards  SRM  1648
       generally duplicated those obtained by
       extraction   procedures,   but   thermal
       desorption is more efficient. It was shown
       that  significant  quantities of polycyclic
       aromatics with heteroatoms, which are
       generally missed by the usual extraction-
       GC-MS   technique,  are   present  in
       particulate matter. Whether  these occur
       in nature or were formed on the particles
       after  sample  collection   cannot   be
       ascertained at this time. However, their
       presence in such abundance needs to be
       addressed  in  any   overall   protocol
       involving extraction and subsequent GC-
       MS analysis.
  Some preliminary experiments with a
state-of-the-art quadrupole mass spec-
trometer have indicated that the number
and  quantity of  organic  species  in
particulate matter  may be even higher
than indicated by the mass-limited scans
made with the quantitative direct probe
mass spectrometric technique.
  It  is recommended  that direct probe
thermal desorption mass  spectrometer
studies should be continued in order to
better  define the  limitations  of  the
technique and to  develop temperature
programming  which will  enhance
thermal fractionation of organic species.
It does not seem possible at this time to
fully identify and quantify all the therm-
ally  desorbed  species  in  particulate
matter.  Consequently,  future  efforts
should be directed  toward simplification
of  the  mass  spectra  by  careful
temperature control. Possible simplifica-
tion in compound identification should be
explored   through   the  utilization  of
chemical ionization  with several different
reagent gases. Additional studies directly
comparing the thermal desorption/MS
approach with conventional extraction/
GC  or GC/MS approaches  should  be
conducted.
         C. A. Alexander. J. R. Hoy land. R. H. Barnes, and J. S. Ogden are with Bane He
           Columbus Laboratories. Columbus. OH 43201.
         D. R. Scott and R. G. Lewis are the EPA Project Officers (see below).
         The complete report, entitled  "Survey of Direct Analysis Methods for Organic
           Compounds in Particulate Matter," (Order No. PB 84-154 723; Cost: $10.00,
           subject to change) will be available only from:
                 National Technical Information Service
                 5285 Port Royal Road
                 Springfield, VA 22161
                 Telephone: 703-487-4650
         The EPA Project Officers can be contacted at:
                 Environmental Monitoring Systems Laboratory
                 U.S. Environmental Protection Agency
                 Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
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