Volatile Petroleum Hydrocarbon (VPH)
Analysis: An Evaluation of the Potential for
False Positive Bias
Presented by:
1
Richard J. Rago; Haley & Aldrich
IPEC
Jane Parkin Kullmann; Haley & Aldrich
31 October 2012
Haley & Aldrich, Inc.
Outline
• Overview of petroleum analytical methods
• VPH method specifics, integration, calculation, and
adjustments
• 2000 and 2011 studies of false positives
• Current Case Study
• Alternative Strategies
2
Haley & Aldrich, Inc.
Analytical approaches to quantitation of
petroleum-related compounds
• Releases of petroleum products comprise a major source
of environmental contamination
• Although petroleum products may contain complex and
variable mixtures of hydrocarbons, some states still rely on
traditional, inexact analytical approaches for petroleum
identification and quantitation – e.g.:
• indicator compounds (i.e., BTEX)
• a single “Total Petroleum Hydrocarbon” (TPH) concentration
• Analyses for BTEX and TPH provide little or no information
on the specific hydrocarbon composition or toxicity of
various petroleum products
3
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Chromatogram of diesel (typical)
Key point: varying results achieved with BTEX and TPH
4
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Initial development of VPH and EPH
methods in Massachusetts
• Interim Final Petroleum Report: Development of HealthBased Alternative to the Total Petroleum Hydrocarbon
(TPH) Parameter (Massachusetts Department of
Environmental Protection, 1994)
• Draft methods released (1995)
• Implementation of VPH/EPH Approach issues paper (1996)
• Characterizing Risks Posed by Petroleum Contaminated
Sites: Implementation of the MADEP VPH/EPH Approach
FINAL POLICY; October 31, 2002; Policy #WSC-02-411
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Haley & Aldrich, Inc.
EPH/VPH analysis
• MassDEP Petroleum Analytical Methods:
• Gas chromatography (GC) methods:
• Volatile Petroleum Hydrocarbons (VPH) method
• Extractable Petroleum Hydrocarbons (EPH) method
• Toxicological-based approach to characterize and evaluate risks
posed by petroleum sites
• Approach included analysis of target compounds with fractionation of
petroleum into collective aliphatic and aromatic carbon ranges
• Methods since updated (May 2004, July 2010 [CAM])
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Representative Petroleum Distillates
Gasoline
No. 2 Fuel Oil/Diesel
No. 6 Fuel Oil
Gasoline Range Org (GRO)
Diesel Range Organics (DRO)
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Haley & Aldrich, Inc.
Overview of Petroleum Hydrocarbons
Petroleum Analytical Methods
Approx. Soil Vapor Survey Range
8015 Headspace
418.1 Infrared (IR)
Gasoline Range Org (GRO)
Diesel Range Organics (DRO)
VPH
EPH
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VPH analysis described elsewhere
• Recognizing the limitations of “indicator only” approaches,
several regulatory entities have promulgated draft and final
methodologies that attempt to better characterize the risks
posed by all hydrocarbons present
• Maine Department of Environmental Protection
• Washington Department of Ecology
• Connecticut Department of Environmental Protection “RCPs”
• Indiana Department of Environmental Management
• NH (soon), LA, TX (TX1006), CA draft LUFT, FLA (MA)
• WI (WI GRO TVPH), MT, NC
• British Columbia Ministry of Environment and Europe (EUGRIS)
• Used elsewhere
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VPH analysis described elsewhere (cont.)
• MassDEP VPH method (without alteration)
• Connecticut
• Maine
• North Carolina (for water; soil methods are various)
• MassDEP VPH method with modifications
• Washington
• Montana
• EPA TPH Method 8015D
• Indiana
• FID analysis only
• British Columbia
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Focus on MassDEP VPH method
• MassDEP VPH Quantitation
• Target Analytes:
• Benzene, toluene, ethylbenzene, o-xylene,
m/p-xylenes (BTEX)
• Methyl tert-butyl ether (MTBE)
• Naphthalene
• Carbon ranges:
• C5-C8 aliphatic hydrocarbons
• C9-C12 aliphatic hydrocarbons
• C9-C10 aromatic hydrocarbons
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Haley & Aldrich, Inc.
VPH calibration for targets
Methyl-t-butyl ether
Benzene
Toluene
Ethylbenzene
m-Xylene
p-Xylene
o-Xylene
Naphthalene
area of peak
Calibratio n Factor (CF) =
concentrat ion purged ( µg / L)
2,5-Dibromotoluene (surrogate)
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Haley & Aldrich, Inc.
VPH calibration for carbon ranges
Pentane
2-Methylpentane
2,2,4-Trimethylpentane
n-Nonane
n-Decane
n-Butylcyclohexane
1,2,4-Trimethylbenzene
Area summation of range components
Range CF =
Total concentrat ion purged ( µg / L)
2,5-Dibromotoluene (surrogate)
Since erratic performance noted for n-nonane; calibration of C9-C12 aliphatics with n-decane and n-butylcyclohexane only is
allowed; n-nonane retained in the calibration standard for use as a range marker compound.
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VPH method peak integration methods
When quantifying on a peak area basis by external calibration,
collective peak area integration for the hydrocarbon ranges must be
from baseline (i.e., must include the unresolved complex mixture
"hump" areas). For the integration of individual Target VPH Analytes,
surrogate compounds, and internal standards, a valley-to-valley
approach should typically be used, though this approach may be
modified on a case-by-case basis by an experienced analyst. In any
case, the unresolved complex mixture “hump” areas must not be
included in the integration of individual Target VPH Analytes and
surrogate compounds. (source: MassDEP vph0504)
valley to valley for targets
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baseline to baseline for C-ranges
Haley & Aldrich, Inc.
Chromatogram of lubricating oil (typical)
Key point: note “hump” area not included, since this
chromatogram is not integrated from baseline.
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Haley & Aldrich, Inc.
Chromatogram of VPH calibration
standards on both detectors
FID
T
B
X
E X X
N
mtbe
PID
Source: MassDEP vph0504
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VPH carbon ranges for gasoline standard
FID
PID
Source: MassDEP vph0504
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VPH method data adjustments
• By definition, the collective concentrations of aliphatic
and aromatic fractions of interest exclude the individual
concentrations of Target VPH Analytes
• Individual concentrations of the Target VPH Analytes are
subtracted from the appropriate aliphatic range in which
they elute
• mtbe, benzene, and toluene concentrations are subtracted from
C5-C8 aliphatic hydrocarbons
• ethylbenzene and o-, m, and p-xylenes are subtracted from
C9-C12 aliphatic hydrocarbons
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VPH method data adjustments (continued)
• the collective concentration of C9-C10 Aromatic Hydrocarbons are
subtracted from the collective concentration of C9-C12 Aliphatic
Hydrocarbons
• C9-C10 aromatics are not adjusted (nothing to adjust from them)
• naphthalene and 2,5-dibromotoluene (surrogate) elute after C9-C12
range (nothing to adjust them from)
• method specifies subtraction of the area counts of surrogate
compound(s) from the collective area count of any range in which
they elute (not applicable if the recommended surrogate
2,5-dibromotoluene is used)
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MassDEP VPH method language
• Method “Scope and Application” recognizes that like all GC
procedures, this method is subject to a "false positive" bias
(from non-targeted hydrocarbon compounds). Confirmatory
analysis is recommended if an applicable reporting or
cleanup standard is exceeded and/or where co-elution of a
non-targeted hydrocarbon compound is suspected.
• Method-described interferences also reference that all
compounds eluting on the PID chromatogram after
o-xylene are identified by the method as aromatic
hydrocarbons (resulting in the potential for overestimation
of levels of aromatic hydrocarbons if late-eluting aliphatic
compounds also respond to the PID).
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Studies of the VPH analytical method
• Two different studies of the VPH method, each done twice
• 2000 (five laboratories)
• 2011 (four laboratories)
• One blind study included the analysis of aqueous control
samples spiked only with halogenated ethanes
• One blind study included the analysis of aqueous control
samples spiked only with aromatic hydrocarbons
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Purpose of studies
• Confirm whether chlorinated VOCs are reported in VPH,
and if so, assess what approximate concentration of
common chlorinated VOCs would trigger a “false”
regulatory response requirement as petroleum
• Assess whether aromatics alone will result in an aliphatic
“remainder” result and if so, would they trigger a “false”
regulatory response requirement for aliphatics
• Determine whether laboratories will be inclined to advise
the data user of these conditions
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VPH study with haloethanes
2000 and 2011
• Aqueous control samples spiked at 50 µg/L and 100 µg/L
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Chloroethane
1,1,1,2-tetrachloroethane
1,2-dibromoethane
1,1,2,2-tetrachloroethane
1,1-dichloroethane
tetrachloroethene
1,2-dichloroethane
1,1,1-trichloroethane
1,1-dichloroethene
1,1,2-trichloroethane
Cis-1,2-dichloroethene
trichloroethene
Trans-1,2-dichloroethene
Vinyl chloride
Haley & Aldrich, Inc.
VPH study with aromatics
2000 and 2011
• Aqueous control samples spiked at 24 µg/L and 300 µg/L
24
Benzene
sec-butylbenzene
Toluene
tert-butylbenzene
Ethylbenzene
isopropylbenzene
Xylene (p)
4-isopropyltoluene
Xylene (m)
N-propylbenzene
Xylene (o)
1,2,4-trimethylbenzene
Styrene
1,3,5-trimethylbenzene
n-butylbenzene
naphthalene
Haley & Aldrich, Inc.
VPH analysis – GC columns (2011)
• All labs used Restek RTX-502.2 column
• 105 meter; 0.53 mm ID; 3.0 um film; diphenyl/dimethyl polysiloxane
phase; Restek Cat # 10910
• All labs differed in GC conditions
• Surrogate 2,5-dibromotoluene elution at 25-42 minutes
• One lab also included surrogate 2,3,4-trifluorotoluene
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Haley & Aldrich, Inc.
2000 VPH study analytical data results for
samples spiked with halogenated ethanes
TABLE I
SUMMARY OF WATER QUALITY
DATA
LABORATORY
SAMPLE
DESIGNATION
PREPARATION DATE
A
A
B
B
C
C
D
D
E
E
MCP
HA-2(OW) HA-3(OW) HA-2(OW) HA-3(OW) HA-2(OW) HA-3(OW) HA-2(OW) HA-3(OW) HA-2(OW) HA-3(OW)
Reportable
14-Apr-00 14-Apr-00 14-Apr-00 14-Apr-00 14-Apr-00 14-Apr-00 14-Apr-00 14-Apr-00 14-Apr-00 14-Apr-00
Concentration
RCGW-1
HALOETHANE
MIXTURE
VPH (µg/L)
C5-C8 Aliphatics
300
240
760
231
754
130
290
99
324
310
1000
C9-C12 Aliphatics
700
34
140
ND (100)
ND (100)
ND (50)
ND (50)
28.2
82.7
37
110
C9-C10 Aromatics
200
ND (20)
ND (40)
ND (100)
ND (100)
ND (50)
ND (50)
ND (20)
ND (20)
ND (5)
ND (5)
Methyl tert-butyl ether
70
ND (5)
ND (10)
ND (5)
ND (5)
ND (5)
ND (5)
ND (2)
ND (2)
ND (5)
ND (5)
Benzene
5
ND (1)
ND (2)
ND (5)
ND (5)
ND (5)
ND (5)
ND (2)
ND (2)
ND (5)
ND (5)
Toluene
1,000
ND (5)
ND (10)
ND (5)
ND (5)
ND (5)
ND (5)
ND (2)
ND (2)
ND (5)
ND (5)
700
ND (5)
ND (10)
ND (5)
ND (5)
ND (5)
ND (5)
ND (2)
ND (2)
ND (5)
ND (5)
Ethylbenzene
Xylenes, mixture
Naphthalene
5,000
ND (5)
ND (10)
ND (5)
ND (5)
ND (5)
ND (5)
ND (2)
ND (2)
ND (5)
ND (5)
140
ND (5)
ND (10)
ND (5)
ND (5)
ND (5)
ND (5)
ND (20)
ND (20)
ND (5)
ND (5)
NOTES AND ABBREVIATIONS:
1. Bold values indicate an exceedance of Method 1 (ALIPHATIC) criteria.
2. ND(2.5): Not detected; number in parentheses is the laboratory reporting limit.
3. VPH: Volatile Petroleum Hydrocarbons
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Haley & Aldrich, Inc.
2011 VPH study analytical data results for
samples spiked with halogenated ethanes
TABLE I
SUMMARY OF WATER QUALITY DATA
LABORATORY
SAMPLE DESIGNATION
PREPARATION DATE
F
F
MCP
HA-101 (OW) HA-102 (OW)
Reportable
04-Aug-11
04-Aug-11
Concentration
RCGW-1
G
HA-101
(OW)
04-Aug-11
G
HA-102
(OW)
04-Aug-11
120
ND (50)
ND (50)
ND (1)
ND (1)
ND (1)
ND (1)
ND (3)
ND (5)
260
ND (50)
ND (50)
ND (1)
ND (1)
ND (1)
ND (1)
ND (3)
ND (5)
H
H
HA-101 (OW) HA-102 (OW)
04-Aug-11
04-Aug-11
J
HA-101
(OW)
04-Aug-11
J
HA-102
(OW)
04-Aug-11
146 a
ND (50)
ND (50)
ND (1)
ND (2)
ND (2)
ND (2)
ND (4)
ND (3)
292 a
ND (50)
ND (50)
ND (1)
ND (2)
ND (2)
ND (2)
ND (4)
ND (3)
HALOETHANE
MIXTURE
VPH (µg/L)
C5-C8 Aliphatics
C9-C12 Aliphatics
C9-C10 Aromatics
Methyl tert-butyl ether
Benzene
Toluene
Ethylbenzene
Xylenes, mixture
Naphthalene
300
700
200
70
5
1,000
700
5,000
140
155
ND (50)
ND (50)
ND (3)
ND (2)
ND (2)
ND (2)
ND (4)
ND (4)
346
66.8
ND (50)
ND (3)
ND (2)
ND (2)
ND (2)
ND (4)
ND (4)
230
ND (100)
ND (100)
ND (1)
ND (1)
ND (1)
ND (1)
ND (3)
ND (5)
440
110
ND (100)
ND (1)
ND (1)
ND (1)
ND (1)
ND (3)
ND (5)
a: “Value includes
chlorinated ethylenes
which are present in
sample matrix.”
NOTES AND ABBREVIATIONS:
1. Bold values indicate an exceedance of Method 1 (ALIPHATIC) criteria.
2. ND(2.5): Not detected; number in parentheses is the laboratory reporting limit.
3. VPH: Volatile Petroleum Hydrocarbons
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VPH study results for halogenated
ethane-spiked samples
• 2000 study
• Range of C5-C8 aliphatics concentrations detected:
• 99 to 310 µg/L in sample spiked at 50 µg/L level
• 290 to 1,000 µg/L in sample spiked at 100 µg/L level
• Range of C9-C12 aliphatics concentrations detected:
• 28.2 to 37 µg/L in sample spiked at 50 µg/L level and 82.7 to 110 µg/L
in sample spiked at 100 µg/L level
• 2011 study
• Range of C5-C8 aliphatics concentrations detected:
• 120 to 230 µg/L in sample spiked at 50 µg/L level
• 260 to 440 µg/L in sample spiked at 100 µg/L level
• Range of C9-C12 aliphatics concentrations detected:
• C9-C12 aliphatics not detected in sample spiked at 50 µg/L level and
66.8 to 110 µg/L in sample spiked at 100 µg/L level
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Example chromatogram for halogenated
ethane-spiked sample
C5-C8 Aliphatics
C9-C12 Aliphatics
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Haley & Aldrich, Inc.
2000 VPH study analytical data results for
samples spiked with aromatic hydrocarbons
TABLE II
SUMMARY OF WATER QUALITY DATA
LABORATORY
SAMPLE DESIGNATION
PREPARATION DATE
A
MCP
HA-2(OW)
Reportable
14-Apr-00
Concentration
RCGW-1
A
HA-3(OW)
14-Apr-00
B
HA-2(OW)
14-Apr-00
B
HA-3(OW)
14-Apr-00
C
HA-2(OW)
14-Apr-00
C
HA-3(OW)
14-Apr-00
D
HA-2(OW)
14-Apr-00
D
HA-3(OW)
14-Apr-00
E
HA-2(OW)
14-Apr-00
E
HA-3(OW)
14-Apr-00
350
2300
1900
ND (10)
260
270
240
1150
280
ND (100)
ND (100)
213
ND (5)
21.6
23.9
23.5
77.4
21.2
486
365
2140
ND (5)
272
302
287
811
272
ND (50)
130
150
ND (5)
20
22
20
91
17
320
1300
1800
ND (25)
250
270
250
1100
260
ND (20)
40.7
160
ND (20)
22.2
21.8
19.2
92.8
23.7
168
ND (100)
2560
ND (100)
284
277
248
1144
353
ND (50)
66
210
ND (5)
24
24
25
69
25
510
850
2400
ND (5)
290
300
290
860
300
AROMATICS MIXTURE
VPH (µg/L)
C5-C8 Aliphatics, Adjusted
C9-C12 Aliphatics, Adjusted
C9-C10 Aromatics
Methyl tert-butyl ether
Benzene
Toluene
Ethylbenzene
Xylenes, mixture
Naphthalene
300
700
200
70
5
1,000
700
5,000
140
34
230
190
ND (5)
26
27
25
111
23
NOTES AND ABBREVIATIONS:
1. Bold values indicate an exceedance of Method 1 (ALIPHATIC) criteria.
2. ND(2.5): Not detected; number in parentheses is the laboratory reporting limit.
3. VPH: Volatile Petroleum Hydrocarbons
Haley & Aldrich, Inc.
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Haley & Aldrich, Inc.
2011 VPH study analytical data results for
samples spiked with aromatic hydrocarbons
TABLE II
SUMMARY OF WATER QUALITY DATA
LABORATORY
SAMPLE DESIGNATION
PREPARATION DATE
F
F
G
MCP
HA-1 (OW)
HA-2 (OW)
HA-1 (OW)
HA-2 (OW) HA-1 (OW) HA-2 (OW) HA-1 (OW) HA-2 (OW)
G
H
H
J
Reportable
04-Aug-11
04-Aug-11
04-Aug-11
04-Aug-11
ND (50)
198
295
415
ND (50)
65
ND (500)
660
04-Aug-11 04-Aug-11 04-Aug-11
J
04-Aug-11
Concentration
RCGW-1
AROMATICS MIXTURE
VPH (µg/L)
C5-C8 Aliphatics, Adjusted
C9-C12 Aliphatics, Adjusted
300
700
ND (100)
180
620
1700
ND (50)
ND (50)
374
243
C9-C10 Aromatics
200
196
330
170
1900
150
1600
189
1830
Methyl tert-butyl ether
70
ND (3)
ND (15)
ND (1)
ND (10)
ND (1)
ND (1)
ND (1)
ND (1)
Benzene
5
23.3
136
24
270
22
270
26.2
292
Toluene
1,000
23.6
88.1
24
280
22
270
26.1
292
700
23.9
95.7
23
270
22
260
26
287
5,000
69.4
277.5
117
1380
66
770
107.8
1174
140
19.7
158
24
290
22
270
21.1
271
Ethylbenzene
Xylenes, mixture
Naphthalene
NOTES AND
ABBREVIATIONS:
1. Bold values indicate an exceedance of Method 1 (ALIPHATIC) criteria.
2. ND(2.5): Not detected; number in parentheses is the laboratory reporting limit.
3. VPH: Volatile Petroleum Hydrocarbons
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VPH study results for aromatic
hydrocarbon-spiked samples
• 2000 Study
• Range of ADJUSTED C5-C8 aliphatics concentrations detected:
• Not Detected to 34 µg/L in samples spiked at 24 µg/L and 168 to 510 µg/L in
samples spiked at 300 µg/L
• Range of ADJUSTED C9-C12 aliphatics concentrations detected:
• 40.7 to 230 µg/L in sample spiked at 24 µg/L
• 365 to 2,300 µg/L in sample spiked at 300 µg/L
• 2011 Study
• Range of ADJUSTED C5-C8 aliphatics concentrations detected:
• Not Detected in sample spiked at 24 µg/L and 295 to 620 µg/L in sample
spiked at 300 µg/L
• Range of ADJUSTED C9-C12 aliphatics concentrations detected:
• 65 to 198 µg/L in sample spiked at 24 µg/L
• 243 to 1,700 µg/L in sample spiked at 300 µg/L
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Example chromatogram for aromatic
hydrocarbon-spiked sample
peaks highlighted by arrows suggest possible coelution of styrene with o-xylene
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Haloethane VPH study results summary
• Haloethane study results confirm that common chlorinated
volatile organic compounds (cVOCs) are reported as VPH
aliphatic hydrocarbons
• In general, approximately 1 mg/L total cVOCs may result in
reported C5-C8 aliphatics that exceed one or more
MassDEP Method 1 risk criteria
• Chromatograms suggest that low boiling cVOCs do not
interfere and that less common, higher boiling cVOCs elute
in the C9-C12 range
• By inference, the presence of many other non-target VOCs
could result in false positive VPH results (e.g., methyl ethyl
ketone)
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Aromatic VPH study results summary
• Aromatic study results confirm that common aromatic
volatile organic compounds are reported as VPH aliphatic
hydrocarbons (remainder effect)
• In general, approximately 2.7 mg/L total non-target
aromatic VOCs may result in reported C5-C8 and C9-C12
aliphatics that exceed one or more MassDEP Method 1
risk criteria
• By inference, the presence of other non-target VOCs could
result in false positive VPH results (e.g., alkenes)
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Current case study
• Concentrations of 1,2-dichloroethane in monitoring well
in excess of regulatory criterion (>500,000 µg/L)
• VPH analysis also indicate C5-C8 aliphatics in excess
of regulatory criterion (>175,000 µg/L)
• Data were CAM Compliant (have “Presumptive
Certainty” per MassDEP) with acceptable QC; no nonconformances present
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Current case study - 8260 chromatogram
xxxxxxxxxxx
source: CAM 8260 analysis of groundwater
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Current case study – VPH chromatogram
(PID)
source: CAM VPH analysis of groundwater
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Current case study – VPH chromatogram
(FID)
source: CAM VPH analysis of groundwater
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Case study outcome
• Internal review of data indicate that the VPH C5-C8
aliphatic results are due to the presence of
1,2-dichloroethane
• Laboratory reissued report; VPH C5-C8 aliphatics results
were adjusted by subtracting the native sample Method
8260 result for 1,2-dichloroethane
• revised VPH C5-C8 aliphatics result is appropriately ND
• All data adjustments documented and narrated
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Alternative VPH methodology draft
• Current VPH methodology utilizes GC to differentiate the
aromatic and aliphatic fractions by their differing responses
to the FID and PID
• compound identifications determined by GC retention time
• non-petroleum compounds with the “right retention times” can be
included
• New pending VPH methodology alternative based on
GC/MS
• similar to APH analysis
• GC/MS VPH method should be capable of better distinguishing
non-petroleum compounds
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Summary and Recommendations
• VPH Method is a better method than TPH for characterizing
petroleum hydrocarbons and thus estimating risk
• Because VPH is a GC method:
• Common chlorinated hydrocarbons, is present, will respond and be
reported as VPH (C5-C8 aliphatics and/or C9-C12 aliphatics)
• Aromatic hydrocarbons can “survive” the method adjustment and be
reported in the “corrected” values as C5-C8 aliphatics and C9-C12
aliphatics
• Careful subtraction in the data can be performed to get a more
accurate picture
• One alternative is to request GC/MS analysis if offered by your
lab…it can better resolve what constituents are actually
petroleum-related
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Conclusions
• Conducting solely VPH analysis may result in a “false
positive” result for petroleum-related compounds
• Current GC methods do not include a requirement to
advise you of “qualitative” matters such as peak patterns
• Common cVOCs or aromatics may trigger response
actions for petroleum when “true” condition would be
attributable to cVOCs or aromatics
• Select analytical methods based on your understanding of
site contaminants of concern
• The potential for “false positive” results should also apply
similarly to EPH analysis (e.g., phthalates)
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