United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S2-86/092 Dec. 1986
v°/EPA Project Summary
Supercritical Fluid
Chromatography for High
Molecular Weight Organic
Analysis
B. W. Wright, H. R. Udseth, and R. D. Smith
This report describes a preliminary
application of supercritical fluid mass
spectrometry (MS) techniques devel-
oped at Battelle-Northwest to the anal-
ysis of a middle distillate fuel, an emis-
sion particulate extract, and the
emission particulates themselves.
These techniques include capillary
column supercritical fluid chromatogra-
phy (SFC) (alone) and coupled with MS,
direct fluid injection (DFD/MS, and su-
percritical fluid extraction (SFE)/MS.
These techniques are still in an early
stage of development, but have
demonstrated considerable potential
for difficult analytical problems. The
present work demonstrates the feasi-
bility of achieving high resolution sepa-
rations of complex mixtures with SFC
using nonpolar CO2 as the mobile
phase. Additionally, these analyses
have provided an evaluation of the lim-
itations of the present detector inter-
faces, resulted in further design im-
provements, and emphasized research
areas for further investigation. The
present work also demonstrates that
SFC/MS application to complex mix-
tures can provide good separations and
usable mass spectra. DFI/MS using su-
percritical ammonia was used to pro-
vide an efficient method of transporting
sample components to the ionization
source to obtain accurate molecular
weight distribution data and structural
information for rapid analysis of materi-
als for which suitable separations have
not yet been developed. Finally, high
molecular species up to mass 1400 amu
were detected during SFE/MS of the
emission particulates using supercriti-
cal ammonia. The necessary research
required to elevate the various super-
critical fluid methods to routine appli-
cation is summarized.
This Project Summary was devel-
oped by EPA's Air and Energy Engineer-
Ing Research Laboratory, Research Tri-
angle Park, NC, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report or-
dering information at back).
Summary
This report describes and summa-
rizes an initial application of supercriti-
cal fluid analytical techniques for the
analysis of complex mixtures. These
techniques are capillary column SFC/
MS, DFI/MS, and SFE/MS. These tech-
niques are all in a relatively early stage
of development, but show significant
promise for application to previously in-
tractable problems or for considerable
simplification of established method-
ologies. The advantages of these tech-
niques include greatly enhanced chro-
matographic resolution compared to
high performance liquid chromatogra-
phy (HPLC) and improved operation
and compatibility with MS.
The present work demonstrates the
feasibility of achieving high resolution
separations of complex mixtures of
moderate molecular weight (e.g., mid-
dle distillate fuel) samples using capil-
lary column SFC and nonpolar C02 as
the mobile fluid. Flame ionization detec-
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tion (FID) was also employed and pro-
vided an efficient form of detection. Sig-
nificant components of even the more
polar nitrogen-containing polycyclic
aromatic hydrocarbons and the hydrox-
ylated polycyclic aromatic materials
were successfully chromatographed.
Coupled capillary column SFC/MS also
proved to be successful for the analysis
of the middle distillate fuel. Although
the separation efficiency was somewhat
less with MS detection, design improve-
ments were earmarked which will
greatly improve the interface perform-
ance and produce results comparable to
FID. Chemical ionization (Cl) mass spec-
tra were also obtained for selected com-
ponents in the middle distillate fuel. In
order to elute high molecular weight
nonvolatile compounds, further im-
provements in the chromatographic in-
terface are necessary and the use of
more polar fluid systems needs to be
developed. The use of polar fluid sys-
tems necessitates expanded develop-
ment of compatible capillary cloumn
technology. The present work also
demonstrates the utility of DFI/MS for
the introduction of sample solutes to
the mass spectrometer. These tech-
niques can provide the basis for new
rapid analysis methods, particularly in
conjunction with tandem MS tech-
niques (e.g., MS/MS). Essentially, any
solute that is soluble in the supercritical
fluid is transported to the ion source in
DFI/MS. In this work, supercritical am-
monia was used to transport and obtain
Cl spectra of the middle distillate fuel,
chemical class fractions of the fuel, and
of the emission particulate extract.
Since these are complex mixtures the
spectra were also complex, but molecu-
lar weight distribution data and some
structural information were obtainable.
MS/MS methods and/or high resolution
MS would greatly aid in the interpreta-
tion of these such spectra for detection
of particular components of interest. Fi-
nally, DFE/MS of the emission particu-
late sample with polar ammonia
demonstrated that material up to mass
1400 amu were extractable. It appears
that the DFI-MS method can be ex-
panded to higher m/z values. The me
spectra which were obtained are co
plex and additional investigation an t
use of expanded techniques such
MS/MS or high resolution MS will
necessary to fully exploit this techniqi
The present work clearly demo
strates the promising potential of S
and SFC/MS techniques for enhanc
analytical characterization of "difficu
samples. Further research will increa
the utility of these methods as an c
panded base of understanding and i
fined instrumentation are developed.
B. Wright, H. Udseth, and R. Smith are with Battelle, Pacific Northwest
Laboratories, Rich/and, WA 99352.
Merrill D. Jackson is the EPA Project Officer (see below).
The complete report, entitled "Supercritical Fluid Chromatography for High
Molecular Weight Organic Analysis," (Order No. PB 87-110 524/AS; Cost:
$13.95, 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 Officer can be contacted at:
Air and Energy Engineering Research 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
Penalty for Private Use $300
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