This document discusses molecular and isotopic fingerprinting techniques to characterize and differentiate between petroleum products. Gas chromatography coupled with flame ionization detection (GC-FID) is used to obtain fingerprints of n-alkanes and polycyclic aromatic hydrocarbons (PAH) to determine their relative abundances. Gas chromatography interfaced with isotope ratio mass spectrometry (GC-IRMS) provides isotopic signatures of n-alkanes by measuring carbon isotope ratios. These molecular and isotopic fingerprints can uniquely identify different petroleum entities and help determine their source and refinement history.

1. Molecular and Isotopic Fingerprinting of Hydrocarbons in
Different Petroleum Entities
Clara Kamel, Anic Imfeld, Yves Gélinas
INTRODUCTION
CONCLUSION
Ø What
is
Petroleum?
Ø Why
do
refined
oils
have
different
hydrocarbon
composi9ons?
PETROLEUM
HYDROCARBONS
C6-­‐C60
Saturates
Naphthenes
(Cycloalkanes)
Paraffins
(branched
+
n-­‐alkanes)
Olefins
Aroma5cs
(BTEX,
PAH)
NON-­‐
HYDROCARBONS
(N,O,S)
organic
compounds
+
Metallics
Group
Gasoline
Diesel
Light
Crude
Bunker
Jet
Fuel
Saturates
50-­‐60
65-­‐95
55-­‐90
20-­‐40
70-­‐80
Olefins
5-­‐10
0-­‐10
-­‐
-­‐
-­‐
Aroma9cs
25-­‐40
5-­‐25
10-­‐35
30-­‐50
30-­‐20
Ø Figure
1:
Qualita9ve
Chemical
Composi9on
of
Petroleum
Δ13C
signatures
of
n-­‐alkanes
using
GC-­‐IRMS
The
alkanes
emerged
from
the
GC
column
and
were
introduced
into
a
CuO
furnace
where
they
were
successively
combusted
to
CO2
before
entering
the
ion
source
of
IRMS.
The
intensi9es
of
masses
44,
45
and
46
corresponding
to
12C16O2,13C16O2and
12C18O16O,
respec9vely,
were
measured
simultaneously,
from
which
the
13C/12C
ra9os
were
determined.
Two
correc9ons
were
applied
to
the
δ13C
values
of
n-­‐alkanes.
For
calibra9on
of
δ13C
values
of
the
standards,
a
CO2
reference
gas
was
automa9cally
introduced
into
the
IRMS
before
and
aaer
n-­‐alkane
peaks.
The
n-­‐alkane
sample
injec9ons
and
the
IRMS
measurements
were
repeated
two
9mes.
0
10000
20000
30000
40000
50000
60000
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
27
Concentra5on
(ppm)
Number
of
Carbons
n-­‐Alkane
Fingerprint
Gasoline
Diesel
Jet
Fuel
Crude
Bunker
0
500
1000
1500
2000
2500
3000
Concentra5on
(ppm)
PAH
Fingerprint
Gasoline
Diesel
Jet
Fuel
Crude
Bunker
-­‐33
-­‐31
-­‐29
-­‐27
-­‐25
-­‐23
-­‐21
-­‐19
-­‐17
-­‐15
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
δ
13C/δ
12C
(per
mil)
Number
of
Carbons
Crude
oil
Bunker
Gasoline
Diesel
Jet
Fuel
APPLICATION
Molecular
Signature
of
n-­‐alkanes
and
PAH
Isotopic
signature
of
n-­‐alkanes
GC-­‐FID
trace
of
n-­‐alkanes
in
Diesel
GC-­‐FID
trace
of
n-­‐alkanes
in
Crude
oil
GC-­‐FID
trace
of
PAH
in
Jet
fuel
GC-­‐FID
trace
of
PAH
in
Bunker
Ø Table
1:
Typical
hydrocarbon
composi9on
in
(%)
of
different
petroleum
products
(1)
These
differences
in
concentra9ons
of
oil
cons9tuents
allow
a
unique
chemical
fingerprint
for
each
petroleum
en9ty.
Ø Figure
2:
Frac9onal
dis9lla9on
column
for
the
refinement
of
crude
oil
(modified
from
ref.
5)
The
difference
in
distribu9on
of
the
saturates
and
the
aroma9cs
in
each
refined
oil
depends
on
two
factors:
Ø The
source
(where
the
oil
was
extracted)
Ø The
refinement
process
Crude
oil
is
converted
into
petroleum
products
in
a
number
of
steps
in
refineries.
The
first
is
frac9onal
dis9lla9on
at
350
to
400°C.
The
crude
oil
vapors
rise
inside
the
column
(light
hydrocarbons),
while
the
heaviest
hydrocarbons
remain
at
the
bokom.
Ø Chemical
Fingerprin9ng
of
the
Hydrocarbons
Due
to
the
dissimilari9es
in
characteris9cs
of
crude
oil
feed
stocks
and
varia9ons
in
refinery
processes,
refined
oil
products
differ
in
their
chemical
composi9ons.
Molecular
Signature:
GC-­‐FID
fingerprints
à
rela9ve
abundances
of
the
different
hydrocarbons
present.
Isotopic
Signature:
CSIA
(compound-­‐specific
isotope
ra9o)
à
ra9os
of
naturally
occurring
stable
isotopes
in
individual
organic
compounds
from
environmental
samples
by
GC/IRMS.
n-­‐Alkanes
generally
have
dis9nct
13C/12C
isotope
ra9os
that
reflect
the
source
or
the
nature
of
the
petroleum
product.
The
carbon
isotopic
signature
is
determined
using
the
formula
below
and
the
results
are
reported
as
δ13C
(in
per
mil)
with
respect
to
PDB.
INTRODUCTION
METHODS
Extrac5on
of
hydrocarbons
from
samples
with
column
chromatography
Ø n-­‐Alkanes
eluted
with
hexane
Ø PAH
eluted
with
dichloromethane
Quan5fica5on
of
n-­‐alkanes
and
PAH
with
GC/FID
(from
C8
to
C40)
Capillary
column:
DB-­‐EUPAH
30
m,
0.25-­‐mm
film
thickness.
Carrier
gas:
Helium
(1
mL/min).
Compound
iden9fica9on:
based
on
GC
reten9on
9mes
of
authen9c
standards,
injected
and
analyzed
under
the
same
condi9ons
as
samples.
Samples
were
run
in
triplicates,
with
the
average
value
and
standard
devia9on
reported.
Ø CSIA
shows
that
the
n-­‐alkane
carbon
isotopic
composi9ons
are
different
in
these
refined
oils.
Ø The
low
MW
n-­‐alkanes
(C8-­‐C16)
will
not
be
used
because
they
are
highly
vola9le
(poten9al
for
mass-­‐
dependent
isotopic
frac9ona9on),
and
because
of
coelu9on
issues
which
result
in
spectral
overlap
and
inaccurate
signatures.
Ø The
δ13C
values
are
all
depleted
in
13C
compared
to
the
PDB
reference.
-­‐
For
Diesel
:
-­‐29
to
-­‐22
‰
-­‐
For
Jet
fuel
:
-­‐27
to
-­‐22
‰
-­‐
For
Bunker
:
-­‐30
to
-­‐26
‰
-­‐
For
Crude
oil:
-­‐30
to
-­‐15
‰
-­‐
For
Gasoline:
-­‐24
to
-­‐21
‰
Ø Chemical
fingerprin9ng
was
applied
to
four
refined
oils
(Jet
Fuel,
Diesel,
Gasoline,
Bunker)
as
well
as
crude
oil.
The
petroleum-­‐specific
target
analytes
that
were
chemically
characterized
were
the
n-­‐alkanes
and
PAH.
They
were
successfully
iden9fied
and
quan9fied
in
each
petroleum
en9ty
using
GC/FID.
Ø CSIA
provides
informa9on
regarding
the
source
of
the
different
samples
and
the
effects
of
the
refinement
process
on
the
δ13C
signatures
of
each
n-­‐alkane.
Carbon
isotopic
composi9on
of
high
molecular
weight
n-­‐alkanes
(>
C16)
are
more
useful
in
characteriza9on
of
oil
since
they
are
less
vola9le
and
more
resistant
to
weathering/
evapora9on.
Coelu9on
of
target
peaks
remains
a
complica9on
of
CSIA.
Ø Chemical
fingerprin9ng
of
petroleum
is
a
powerful
tool
in
geochemistry
for
hydrocarbon
source
iden9fica9on.
In
oil
spill
inves9ga9ons,
using
a
single
fingerprin9ng
approach
some9mes
is
not
powerful
enough
to
fully
meet
the
objec9ves
of
forensic
inves9ga9ons
and
quan9ta9vely
associate
hydrocarbons
to
their
sources.
This
is
why
two
techniques
were
employed
in
this
case:
GC/FID
and
GC/IRMS.
Ø Molecular
and
isotopic
measurements
are
also
used
to
study
the
weathering
effect
on
oil
spill
residues.
Ø A
model
integra9ng
both
fingerprint
signatures
will
be
developed
to
allow
differen9a9ng
between
different
contaminants,
and
between
contaminants
and
natural
n-­‐alkanes
present
in
soils
and
sediments.
REFERENCES
1) A.,
S.
S.
(2016).
Standard
handbook
oil
spill
environmental
forensics
fingerprin9ng
and
source
iden9fica9on.
London:
Academic
Press.
2) Murphy,
B.
L.,
&
Morrison,
R.
D.
(2007).
Introduc9on
to
environmental
forensics.
Amsterdam:
Elsevier.
3)
Zhendi
Wang
,
Scok
A.
Stout
&
Merv
Fingas
(2006)
Forensic
Fingerprin9ng
of
Biomarkers
for
Oil
Spill
Characteriza9on
and
Source
Iden9fica9on,
Environmental
Forensics,
7:2,
105-­‐146,
DOI:
10.1080/15275920600667104
4) Frances
D.
Hostekler
,
Thomas
D.
Lorenson
&
Barbara
A.
Bekins
(2013)
Petroleum
Fingerprin9ng
with
Organic
Markers,
Environmental
Forensics,
14:4,
262-­‐277,
DOI:
10.1080/15275922.2013.843611
5) "Trays
and
Plates."
DisAllaAon
Column:
Column
Internals,
Bubble
Cap
Trays,
Valve
Trays,
Sieve
Trays,
Structured
Packing.
N.p.,
2008.
Web.
03
Dec.
2016.
C10
RESULTS/DISCUSSION
C8
C9
C12
C14
C9
C10
C18
C16
C26
C20
C18
C16
C14
C12
C11
C24
C20
*
*
*
*
PAH
*
*
*
*
*
*
*
*
PAH
*
*
*
*
δ13
C =
(
13
C
12
C
)Sample −(
13
C
12
C
)PDB
(
13
C
12
C
)PDB
×1000%