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ENVIRONMENTAL
FORENSICS Poster Session
Optimizing
Purge-and-Trap GC/MS Analysis of Gasoline Range Compounds
for Environmental Forensic Investigations
Edward M. Healey, S. Andrew Smith, Richard M. Uhler,
Scott A. Stout, Kevin J. McCarthy, and Allen D. Uhler,
Battelle Environmental Forensics Group
Fugitive automotive gasoline and other light distillate
petroleum products in the environment commonly result in
liability issues. Consequently, environmental forensic
investigations often attempt to characterize
gasoline-derived contamination with the intent of
distinguishing among gasoline type(s) and, in turn, their
source(s). Since all automotive gasolines share gross
chemical (and physical) features that are required by
internal combustion engines, defensible assessment of the
type(s) of gasoline contamination requires, at its heart,
detailed chemical characterization of the contamination.
Due primarily to irrelevant or limited analyte lists, the
standard EPA Method 8260 or 8020 (BTEX) analyses fall far
short when attempting to distinguish one source of light
fuel from another. Rather, the ability to distinguish
among different gasolines released into the environment
mandates very detailed chemical analysis tailored for
automotive gasoline.
In this poster, an analytical method developed
specifically for gasoline analysis in environmental
matrices for forensic investigations is presented. The
method relies upon modifications to standard
purge-and-trap gas chromatography/mass spectrometry
(PT-GC/MS). It includes an extensive target analyte list
(n ~ 120) that is representative of the diverse array of
complex hydrocarbons and non-hydrocarbons found in blended
automotive gasolines and other light distillate petroleum
products. The comprehensive list includes seven compound
classes, namely paraffins, isoparaffins, aromatics,
naphthenes, olefins, oxygenates and sulfur-bearing
compounds, which can be useful in differentiating among
different types of automotive gasoline. Performance
guidelines have been established to monitor the
chromatography, particularly 'compound class
discrimination', which is defined as the selective
purge-and-trap efficiency of differing classes of volatile
organic, petroleum specific compounds, based on physical
constants such as solubility and molecular weights.
PCBs
Analyzed by Mass Spectrometry (Method 680) - Homolog -
Congener Analysis
Peter J. Kane and Catherine Mosher, The Woods Hole
Group, Inc.
PCBs analyzed by mass spectrometry can remove ambiguity
in identification and quantification that arise using GC/ECD
methods. PCBs that are heavily weathered in the
environment or metabolically converted may not be
identifiable as an aroclor, and go undetected as PCBs in a
sample. Standard methods, such as 8082, may not adequately
classify the contaminate, and potentially negate material
as a PCB. Data presented here uses mass spectrometry to
quantify the PCBs by their homolog groupings.
Identification using mass spectrometry is definitive.
Along with the homologs, individual congeners can be
analyzed as well, for the monitoring of long term PCB
degradation.
Compound-Specific
Carbon Isotope Ratios used in Forensic Studies of Former
Manufactured Gas Plant Sites
David M. Mauro and David R.
Craig, META Environmental, Inc., R. Paul Philp, University
of Oklahoma
Polycyclic aromatic
hydrocarbons (PAHs) often drive costly site investigation
and remediation work. Former manufactured gas plant (MGP)
sites frequently are contaminated by PAHs from one or more
sources depending on their operational histories, and in
many cases the nature of environmental work at MGP sites can
depend on identifying the sources of the PAHs. However,
identifying the sources of
PAH contamination at MGP sites is complicated by the
numerous possible PAH origins. Common anthropogenic sources
of PAHs include coal tar and coal tar products, refined
petroleum products, MGP wastes, exhaust from heating
systems, vehicular emissions, and others. PAHs also are
created naturally by forest fires and, in some cases,
synthetically by bacteria and algae. As PAHs weather and
commingle with PAHs of other origins, as is typically the
case in industrial soils and urban sediments, identifying
their sources proves increasingly difficult.
This paper presents some of
the results of EPRI research to identify effective
environmental forensic methods for application at former MGP
sites.1 The work has partially included a review of
literature on MGP chemistry, the collection and analysis of
samples of MGP tar and other reference materials, and the
testing of several emerging analytical methods for
environmental forensics.
Several analytical tools are
available to environmental forensic chemists for determining
the sources of PAHs at former MGP sites. This presentation
discusses the application of compound-specific carbon
isotope ratios by gas chromatography with isotope ratio mass
spectrometry (GC/IRMS) for the determination of PAH sources
in non-aqueous phase liquids (NAPLs), soil, sediment, and
water. Sample classification by GC/IRMS was compared to
results obtained using
hydrocarbon fingerprinting by GC/FID, extended PAH profiles
by GC/MS, and bulk sample fingerprinting by FTIR. The
isotopic ratio of C13/C12 for 16 parent PAHs was the most
reliable technique for separating sources of PAHs in NAPL,
soil, and sediment for weathered samples, and also was
effective in determining the source(s) of groundwater plumes
of MAHs and PAHs. Differences in carbon isotope ratios were
noted for PAHs derived from coal tar, from oil tars, and
from petroleum products. These differences correlated well
with differences in certain PAH ratios and the amounts in
the samples of other source indicators, such as saturated
hydrocarbons and organic acids. Selected results from MGP
sites will be used to illustrate the value and effectiveness
of the methodology.
1"Chemical Source
Attribution at Former MGP Sites," EPRI Technical Report
1000728, December 2000.
Detailed
Fingerprinting of Automotive Gasoline and Other Light
Distillates by Purge-and-Trap Gas Chromatography/Mass
Spectrometry
Richard M. Uhler, Scott A. Stout, Edward M. Healey,
Kevin J. McCarthy, and Allen D. Uhler, Battelle
Environmental Forensics Group
Historically, the identification and differentiation of
light distillate products (particularly weathered
products) and, to a greater extent, differentiation among
similar light distillates, has been hindered by analytical
and interpretative limitations. While analytical methods
optimized for the measurement of hydrocarbons in the C10
to C40 carbon range exist, current environmental forensic
techniques for petroleum site assessments involving
volatile contaminants are often limited to evaluations of
the major volatile components required for regulatory
assessment purposes (e.g., BTEX or MTBE). These methods
alone are inadequate for forensic investigations involving
light distillate products primarily because they do not
measure the breadth and variety of hydrocarbon and
non-hydrocarbon components in the C4 to C12 range that
make up this class of refined petroleum. Recent
modifications to EPA Method 8260 involving (1)
optimization of purge-and-trap and chromatographic
conditions and (2) expansion of the analyte list to
include a wide variety of diagnostic volatile hydrocarbons
and non-hydrocarbons have been described by our Group.
This improved analytical method provides for the
quantitative analysis of a broad spectrum of volatile
hydrocarbon classes, namely paraffins, isoparaffins,
aromatics, naphthenes and olefins (PIANO) and
non-hydrocarbons (oxygen- and sulfur-containing moieties).
Quantitative data for this spectrum of compounds provides
the forensic investigator with an improved ability to
differentiate and compare automotive gasoline and other
light distillates in the environment. This paper presents
an overview of the key compositional characteristics of
automotive gasoline and other light distillate products,
as revealed by improved purge-and-trap GC/MS analysis,
which allows for their detailed characterization in
environmental forensic studies.
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