The document presents information from a 2011 conference presentation on polycyclic aromatic hydrocarbons (PAHs). PAHs are formed during incomplete combustion and can be found at contaminated sites. Two analytical methods for measuring PAHs in soils are discussed: gas chromatography/mass spectrometry and high-resolution isotope dilution mass spectrometry. A case study compares results from these two methods when analyzing soil samples, evaluating accuracy using a standard reference material and precision using duplicate samples. The high-resolution method showed better accuracy and precision compared to the more common gas chromatography/mass spectrometry method.

1. Presented by Erik Martin, PhD, DABT
2011 SETAC Conference on Nov. 14, 2011
Co-Author: Court D. Sandau, PhD
SETAC 2011 - www.chemistry-matters.com 1

2. 1. BACKGROUND
Polycyclic Aromatic Hydrocarbons

3. *
* PAHs are a complex class of organic compounds containing
two or more fused aromatic rings (only C and H atoms).
* They are primarily formed by incomplete combustion of
carbon-containing fuels - wood, coal, diesel or tobacco.
* Sources
* Anthropogenic: Wood burning, vehicle emissions, industry
* Natural: Forest fires, volcanoes
SETAC 2011 - www.chemistry-matters.com 3

4. *
naphthalene acenaphthene anthracene acenaphthylene phenanthrene f luorene
2-ring 3-ring
chrysene fluoranthene pyrene benzo[a]anthracene benzo[b]fluoranthene
4-ring
benzo[k]fluoranthene dibenz[a,h]anthracene benzo[a]pyrene benzo[ghi]perylene indeno[1,2,3-cd]pyrene
5-ring 6-ring
SETAC 2011 - www.chemistry-matters.com 4

5. Why do we care?
PAHs have been identified as a contaminant of concern at 401
National Priorities List (NPL) sites (roughly one-third of sites)
and are ranked ninth on the CERCLA priority list of hazardous
substances (2011).
SETAC 2011 - www.chemistry-matters.com 5

6. 2. TOXIC EQUIVALENT SCHEME

7. Benzo(a)pyrene Toxic Equivalency – B(a)P TEQ
For mixtures of structurally related chemicals with a common mechanism of
action, use TEQ approach to evaluate the toxicity and assess risk.
B(a)P TEQ are calculated by multiplying the soil conc. of individual PAHs by a
toxic equivalency factor (TEF), and by subsequently summing the B(a)P TEQ
for the entire PAH mixture (total B(a)P TEQ).
TEFs are order of magnitude estimates of toxic potential as compared to
B(a)P; which is given a reference value of 1.
Where:
TEFn = Toxic Equivalency Factor of Individual Congener
Cn = Concentration of Congener in Complex Mixture
SETAC 2011 - www.chemistry-matters.com 7

8. Compound [1] [2] [3] [4] [5] [6] [7]
1-Methylphenanthrene 0.001
Acenaphthene 0.001 0.001 0.001 0
Acenaphthylene 0.001 0.001 0.01
Anthanthrene 0.32 0.28
Anthracene 0.01 0.01 0.01
TEF Sets
Benz[a]anthracene 0.145 0.1 0.1 0.1 0.1 0.1 0.014 [1] Krewski et al. (1989)
Benzo[a]pyrene 1 1 1 1 1 1 1
[2] Nisbet & LaGoy (1992)
Benzo[b]fluoranthene 0.141 0.1 0.1 0.1 0.1 0.1 0.11
Benzo[e]pyrene 0.004 0.01 0
[3] Malcolm & Dobson (1994)
Benzo[ghi]perylene 0.022 0.01 0.01 0.01 0.012 [4] Kalberlah et al. (1995)
Benzo[j]fluoranthene 0.1 0.1 0.045 [5] US EPA (1993)
Benzo[k]fluoranthene 0.061 0.1 0.1 0.1 0.01 0.1 0.037
Chrysene 0.0044 0.01 0.01 0.01 0.001 0.1 0.026
[6] McClure & Schoeny (1995)
Coronene 0.001 [7] Muller et al. (1995a,b, 1996)
Cyclopenta[cd]pyrene 0.023 0.1 0.1 0.012
Dibenzo[a,e]pyrene 1
Others:
Dibenz[a,c]anthracene 0.1
Dibenz[a,h]anthracene 1.11 5 1 1 1 1 0.89 OEHHA (1993)
Dibenzo[a,l]pyrene 100 100 CalEPA (2005)
Dibenzo[a,e]fluoranthene 1
Dibenzo[a,h]pyrene 1 1.2
Dibenzo[a,i]pyrene 0.1
Fluoranthene 0.001 0.001 0.01
Fluorene 0.001 0.001 0
Indeno[1,2,3-cd]pyrene 0.232 0.1 0.1 0.1 0.1 0.1 0.067
Naphthalene 0.001 0.001
Perylene 0.001
Phenanthrene 0.001 0.001 0 0.00064
Pyrene 0.81 0.001 0.001 0.001 0
SETAC 2011 - www.chemistry-matters.com 8

9. PAH Mechanism of Toxicity
NUCLEUS
⇌
AhR hsp90
PAH PAH ARNT ARNT
PAH AhR
hsp90
CYP1A
PAH AhR
XREs
CYP1A mRNA Other mRNAs
apo–CYP1A
ENDOPLASMIC
X
RETICULUM GT EH further
PAH-OH
R CYP1A metabolism
Hepatocyte
PAH
⇌
R = NADPH-cytochrome P450 reductase
EH = epoxide hydroxylase
PAH
GT = glutathione transferase
X = UDP-glucuronosyl transferase
SETAC 2011 - www.chemistry-matters.com 9

10. 3. ANALYTICAL METHODS

11. Analytical Methods
 A number of analytical methods are available to measure
PAHs in various environmental media (including soil).
 Examples:
Gas chromatography/mass spectrometry (GC/MS)
- US EPA Method 8270C
- Standard analytical method
High-resolution isotope dilution mass spectrometry (ID/MS)
- Based on CARB429
- Less common method
SETAC 2011 - www.chemistry-matters.com 11

12. GC/MS
VS.
ID/MS
SETAC 2011 - www.chemistry-matters.com 12

13. *
Low Resolution MS Method High Resolution MS Method
 US EPA Method 8270C  Modified California Method
 Full scan analysis  Selected ion monitoring
 No confirmation ions or ratios  IDMS quantitation
 Inappropriate surrogate  Interferences are less likely
standards  Isotopically labeled standards
 Less sensitive method  More accurate and precise
 Many versions of method
SETAC 2011 - www.chemistry-matters.com 13

14. *
 Many interferences exist in low MW range
– Depends on matrix, cleanup method
 Specificity of HRMS allows better accuracy and
precision
 Comes at a cost – 4 to 6x ($150 vs. $800)
Difference in measuring
252 versus 252.30928
Benzo(a)pyrene
SETAC 2011 - www.chemistry-matters.com 14

15. *
Naphthalene Phenanthrene Benzo(a)pyrene
* *
* *
* *
* *
F
O
N+
O-
Nitrobenzene 2-Fluorobiphenyl p-Terphenyl
SETAC 2011 - www.chemistry-matters.com 15

16. *
 Internal standards behave exactly like compounds
being analyzed
 Loss of analytes during method, included in
measurement (adjust recovery)
 Interferences in method, can usually be seen with
standards as well
 The most accurate measurement available (‘gold
standard’)
SETAC 2011 - www.chemistry-matters.com 16

17. 4. CASE STUDY

18. Case Study
Litigation involving a site with a long history of industrial activity
(inc. tannery/hide treatment, rail operation, manufacturing facilities)
Is more expensive better?
Experiment:
 Sampled 5 locations
 Homogenized and split samples
 Sent 5 for routine PAH analysis
 Sent 5 for ID-HRMS analysis
 SRM – determine accuracy
 Duplicate – determine precision
SETAC 2011 - www.chemistry-matters.com 18

19. *
 How close are the analytical measurements to the ‘true’
values?
 Assessed by measuring a sample with known PAH
concentrations.
- Standard Reference Material
- NIST (National Institute of Standards &Technology)
SETAC 2011 - www.chemistry-matters.com 19

20. Concentration (ng/g)
Ac
en
0.2
0.4
0.6
0.8
1.2
0
1
ap
ht
he
Ac ne
en
ap
ht
hy
le
ne
An
th
Be ra
nz ce
o( ne
a)
an
th
ra
ce
Be ne
nz
o(
Be a)
py
nz re
*
Overestimation
o( ne
b)
flu
SETAC 2011 - www.chemistry-matters.com
or
Be an
Certified SRM Value
nz th
o( en
g, e
h,
i)p
Be er
nz yle
o( ne
k)
f lu
or
HRMS
an
th
en
e
Di Ch
be ry
nz se
20
(a ne
.h
)a
LRMS
nt
hr
ac
en
Fl e
uo
ra
nt
he
ne
In Fl
de uo
no re
(1 ne
,2
.3
Standard Reference Material
-c
2- d)
M py
re
et
hy ne
ln
ap
ht
ha
le
ne
Na
ph
th
al
en
Ph e
en
an
th
re
ne
Py
re
ne

21. Concentration (ng/g)
Ac
en
0.2
0.4
0.6
0.8
1.2
0
1
ap
ht
he
Ac ne
en
ap
ht
hy
le
ne
An
th
Be ra
nz ce
o( ne
a)
an
th
ra
ce
Be ne
nz
o(
Be a)
py
nz re
*
Overestimation
o( ne
b)
flu
SETAC 2011 - www.chemistry-matters.com
or
Be an
Certified SRM Value
nz th
o( en
g, e
h,
i)p
Be er
nz yle
o( ne
k)
f lu
or
HRMS
an
th
en
e
Di Ch
be ry
nz se
21
(a ne
.h
)a
LRMS
nt
hr
ac
en
Fl e
uo
ra
nt
he
ne
In Fl
de uo
no re
(1 ne
,2
.3
Standard Reference Material
-c
2- d)
M py
re
et
hy ne
ln
ap
ht
ha
le
ne
Na
ph
th
al
en
Ph e
en
an
th
re
ne
Py
re
ne

22. *
 Can the laboratory achieve the same analytical result
repeatedly?
 Assessed by evaluating blind duplicates
 Field duplicate - includes sampling error
 Lab duplicate - only laboratory error
 Relative Percent Difference to determine differences
in measurements
SETAC 2011 - www.chemistry-matters.com 22

23. PAH Duplicate Results
HRMS
120
3% 8% 15% 16% 18% 17% 27% 11% RPD
100
Concentration
80
(ng/g)
60
40
20
0
BaA BaP BbF BkF CHRY FLUOR PHEN PYR
LRMS
120
100
100% 92% 111% 100% 86% 94% 101% 90% RPD
Concentration
80
(ng/g)
60
40
20
0
BaA BaP BbF BkF CHRY FLUOR PHEN PYR
SETAC 2011 - www.chemistry-matters.com 23

24. PAH Duplicate Results
HRMS
120
3% 8% 15% 16% 18% 17% 27% 11% RPD
100
Concentration
80
(ng/g)
60
40
20
0
BaA BaP BbF BkF CHRY FLUOR PHEN PYR
LRMS
120
100
100% 92% 111% 100% 86% 94% 101% 90% RPD
Concentration
80
(ng/g)
60
40
20
0
BaA BaP BbF BkF CHRY FLUOR PHEN PYR
SETAC 2011 - www.chemistry-matters.com 24

25. Concentration (ng/g)
Ac
en
ap
100
200
300
400
500
600
700
800
900
1000
0
Ac ht
en he
ap ne
ht
hy
le
Be An ne
th
LRMS Method
HRMS Method
nz ra
o( ce
a) ne
an
th
Be ra
nz ce
Be o( ne
nz a)
o( py
SETAC 2011 - www.chemistry-matters.com
b) re
Be flu ne
nz or
an
o( th
g, en
Be h, e
nz i)p
o( er
k) yle
f lu ne
or
an
th
Di en
be Ch e
nz
(a ry
25
.h se
)a ne
nt
hr
Sample 1-1
ac
Fl en
uo e
ra
nt
In he
de ne
no Fl
(1 uo
,2 re
2- .3 ne
M -c
d)
PAH Analytical Results
et py
hy re
ln ne
ap
ht
ha
Na le
ne
ph
th
Ph al
en
en e
an
th
re
ne
Py
re
ne

26. Total B(a)P TEQ
3500
3000
2500
17,278
32,542
2000
1500
1000
500
0
1-1 9-1 9-3 21-1 22-1
HRMS Method B(a)P guideline for industrial soil
LRMS Method
SETAC 2011 - www.chemistry-matters.com 26

27. *
 Detection limits are 200x lower with ID-HRMS
 When calculating the total B(a)P TEQ, where a PAH
is non-detect, ½DL is used.
if high DLs then overestimate total TEQ.
SETAC 2011 - www.chemistry-matters.com 27

28. HRMS LRMS
g/kg TEF TEQ g/kg TEF TEQ
Acenaphthene 1.37 0.001 0.00137 5 0.001 0.005
Acenaphthylene 2.56 0.001 0.00256 2.5 0.001 0.0025
Anthracene 10.3 0.01 0.103 12 0.01 0.12
Benzo(a)anthracene 32.7 0.1 3.27 60 0.1 6
Benzo(a)pyrene 34.7 1 34.7 46 1 46
Benzo(b)fluoranthene 49.0 0.1 4.9 70 0.1 7
Benzo(g,h,i)perylene 27.8 0.01 0.278 40 0.01 0.4
Benzo(k)fluoranthene 18.8 0.1 1.88 30 0.1 3
Chrysene 33.4 0.01 0.334 50 0.01 0.5
Dibenz(a.h)anthracene 6.81 5 34.05 10 5 50
Fluoranthene 60.7 0.001 0.0607 91 0.001 0.091
Fluorene 7.04 0.001 0.00704 2.5 0.001 0.0025
Indeno(1,2.3-cd)pyrene 26.2 0.1 2.62 30 0.1 3
Naphthalene 14.4 0.001 0.0144 10 0.001 0.01
Phenanthrene 48.4 0.001 0.0484 70 0.001 0.07
Pyrene 51.2 0.001 0.0512 74 0.001 0.074
Total B(a)P TEQ 82.32 116.28
% of TEQ from ½DL 0%
43%
SETAC 2011 - www.chemistry-matters.com 28

29. 5. CONCLUSIONS

30. *
 For measurement of PAHs, ID-HRMS provides
unparalleled resolution, accuracy and precision.
 Contaminated sites driven by PAH risk require the ID-
HRMS method.
– Sensitivity - for guidelines
– Specificity - for interferences that are naturally
present in samples
 The only method that should be used for risk
assessment, contaminated site closure, and litigation.
 LRMS method should be used sparingly or used for
screening purposes only.
SETAC 2011 – for inquiries please visit:
30
www.chemistry-matters.com

31. QUESTIONS