1
presented by
Wayne Einfeld and Gary BrownSandia National Laboratories
Albuquerque, New Mexico USA
Eric KoglinUnited States Environmental Protection Agency
Las Vegas, Nevada USA
Technology Performance Characteristics
for the On-Site Measurement
of Chlorinated Volatile Organic
Compoundsin
Groundwater
2
Presentation Overview
A US EPA Environmental Technology Verification test of field-portable water monitoring instruments is described.
Test results are presented which include the features and performance characteristics of five different on-site instrumental analysis methods for the measurement of chlorinated VOCs in groundwater at contaminated sites.
3
Presentation Outline
Overview of ETV Program and the Site
Characterization and Monitoring
Technology Center
Technology Overviews
Verification Test Design
Verification Test Results
Summary and Conclusions
4
Established by EPA to verify the performance of innovative environmental technologies
Accelerates acceptance and use of improved, cost-effective technologies
Public and private partners to test technologies under EPA sponsorship and oversight
Six Centers including the Site Characterization and Monitoring Technologies Center (SCMT)
Site Characterization and Monitoring Technology Center has Sandia National Laboratories and Oak Ridge National Laboratory as verification testing partners
Environmental Technology Verification (ETV) Program
5
Site Characterization and Monitoring Technologies Center
Our Technology Focus . . .
Verify the performance of technologies that
can be used for generating real-time data or
information to support monitoring of human
and ecosystem health, assessing real or
potential exposure to environmental
contaminants and hazards, for monitoring
environmental conditions, and characterizing
(physically and chemically) contaminated sites
6
SCMT Center Goals
Accelerate the use and acceptance of innovative environmental monitoring and characterization technologies
Rigorous, statistically-defensible testing under actual field conditions
Provide reliable, high-quality performance information
Leverage federal resources and expertise
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What does Verification Mean?
To establish or prove the truth of the
performance of a technology under specific,
predetermined criteria or protocols and adequate
data quality assurance procedures.
8
SCMT Technology Areas
Field analytical technologies– Field portable X-Ray fluorescence
spectrometers– Field portable gas chromatograph/mass
spectrometers– Immunoassay kits– Field portable gas chromatographs– Fiber optic chemical sensors– Alpha detectors– Colorimetric test kits
9
SCMT Technology Areas cont’d
Decision support software systems Physical characterization (e.g., geophysical
methods, direct-push systems) Soil, soil gas, groundwater, surface water,
and sediment sampling methods Technologies for assessing contaminated
structures Monitoring bioremediation and natural
attenuation Toxicity screening methods
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Technology Verification Process
VerificationTest
Planning
VerificationTest
Planning
FieldTesting
FieldTesting
Data Collectionand Validation
Data Collectionand Validation
ReportPreparation
ReportPreparation
FinalReport &
VerificationStatement
FinalReport &
VerificationStatement
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Verification Test Plan Development
Verification Test Plan
12
Verification Org. coordinates
Vendors operate their instruments
Testing at two sites or conditions
“Blind” sample analysis
QA audits during field tests
Verification Testing in the Field
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Technology Verification Report Contents
Verification Statement
Technology Description
Site and Design Description
Reference Laboratory Data Validation
Verification Test Results
Field Observations and Cost Summary
Technology Update
14
Verification of Field Analytical Techniques
for the Measurement VOCs in Water
Goal: Verify field analytical techniques capable of detecting and quantifying chlorinated VOCs in water
Demonstration objectives:
– Obtain performance information using quality control and field samples
– Compare technology results with conventional laboratory results
– Determine logistical requirements for technology use
Data used in this presentation is taken from from published ETV reports (www.epa.gov/etv)
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Five Technologies Were Tested
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Why use these technologies?
Faster, cheaper, better site screening and routine ground water monitoring
Quick-turnaround sampling and analysis enables on-site decisions and dynamic workplans
Less sample handling and paperwork
Reapplication of existing equipment
17
How might these technologies be used?
Field analytical support for direct push investigations
Preliminary groundwater screening at new or existing
wells
Real-time monitoring for plume migration/barrier wall
performance
Routine groundwater monitoring programs for known
compounds at relatively high contamination levels (>10
ug/L)
Soil vapor analysis
Waste water outfall monitoring
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Getting Sample to the Instrument
Equilibrium Headspace- simple- less sensitive- HAPSITE, Voyager, Multi-gas
Monitor
Purge-and-Trap/Thermal Desorption
- more complex- more sensitive- Scentograph Plus II, EST Model 4100
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Equilibrium HeadspaceHenry’s LawAt constant temperature:
[VOC]gas __________ = Henry’s Constant [VOC]liq
Henry’s Constant is compound-specific and is determined by the solubility of the compound in water
Less soluble > Higher headspace concentration More soluble > Lower headspace concentration
A gas sample is withdrawn from the headspace and analyzed by GC. The water concentration is calculated from the gas concentration using Henry’s Constant
Gas PhaseVOC Concentration
Liquid PhaseVOC Concentration
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Dynamic Headspace (Purge-and-Trap)
Purge Gas
Helium
or
Nitrogen
Step 1Purge VOCs from solution and trap on sorbent
Step 2Heat the sorbent trap and sweep the VOCs off the sorbent with the carrier gas
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Carrier
Gas
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Gas Chromatography (GC)
Separates a mixture of compounds (usually organic)
Relies on differing solubilities of the analytes in an organic compound (stationary phase) lining the column wall
Detector at end of column allows separated compounds to be quantified
Retention time and detector response enable compound identification and quantification
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Headspace/Gas Chromatography
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Perkin-Elmer, Voyager
Description: Field-portable GC with multiple columns and dual ECD and PID detectors, isothermal operation
Size, Weight: Small, 48 pounds (with accessories)Sample handling: Completely manualSample throughput: 1-3 samples/hrData processing: pre-programmed automated methods, printed
outputCalibration: pre-deployment calibration, daily check standards Power: Battery or AC Cost: $24KAccessories: Carrier gases, optional PC, syringes, water bathOperator training: 1-2 hours for a chemical technician
24
Perkin-Elmer, Voyager
25
Electron Capture Detector
A “standing current” is produced in the detector by the interaction of a radioactive electron source with the carrier gas.
When electronegative compounds enter the detector they “capture” the electrons and cause a measurable change in the standing current.
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Photoionization Detector
A UV lamp is used to irradiate a heated ionization chamber at the end of a GC column
The UV energy ionizes many organic molecules through a photoionization reaction:
R + h = R+ + e-
The resulting ion current is sensed by an electrometer and is used to quantify the amount of material present
Electrometer
+
–
Power Supply
From GCColumn
Exhaust
UV LampHeated Ionization Chamber
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Sentex Systems Inc., Scentograph Plus II
Description: Field-portable, purge-and-trap GC with micro-argon ion and/or electron capture detector, isothermal or temperature program operation
Size, Weight: Moderate, 80 poundsSample handling: Completely automatedSample Throughput: 2 samples/hourData processing: pre-programmed automated methods, printed
output not readily availableCalibration: Daily three-point, daily check standardsPower: Battery or AC Cost: $35KAccessories: Carrier gases, PCOperator training: Moderate
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Sentex Systems Inc., Scentograph Plus II
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Micro Argon Ion Detector
The detector contains a tritium foil that is used to irradiate the argon carrier gas
Some of the argon molecules become excited (metastable).
The metastable argon ionize the organics
Ar + e– = Ar*
Ar* + R = R+ + e–
The resulting ion current is sensed by an electrometer and is used to quantify the amount of organic material present
Electrometer
+
–
Argon carrier gasfrom GC column
ExhaustTritium Foil
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Electronic Sensor Technology Inc., Model 4100
Description: Field-portable, purge-and-trap GC with surface acoustic wave detector
Size, Weight: Moderate, 35 pounds
Sample Handling: Partially automated
Sample Throughput: 2-3 samples/hour
Data processing: pre-programmed automated methods, printed output
Calibration: pre-deployment 3-point calibration, periodic check standards, internal standard
Power: Battery or AC
Cost: $25K
Accessories: Carrier gases, PC
Operator training: 1 day for experienced chemical technician
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Electronic Sensor Technology Inc., Model 4100
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Surface Acoustic Wave Detector
A surface acoustic wave (SAW) detector operates much like a quartz crystal detector. An AC voltage at the input transducer causes an acoustic wave to propagate across a crystal surface to the output transducer.
Adding mass, such as an analyte from the end of a GC column, onto the detector surface causes a measurable change in the properties of the acoustic wave.
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Inficon Inc., HAPSITE
Description: Field-portable GC-MS and Headspace Sampling Accessory
Size, Weight: Moderate, 75 poundsSample Handling: Partially automatedSample Throughput: 2-3 samples per hourData Processing: pre-programmed automated methods, printed
output Calibration: pre-deployment multi-point, periodic check standard,
internal and surrogate standards, daily MS tune checkPower: Battery or AC Cost: $75-95KAccessories: Calibration and carrier gases, PCOperator training: 1 day of training for an experienced chemical technician
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Inficon Inc., HAPSITE
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GC-Mass Spectrometry
Quadrupole Mass Selective Detector
An electron beam ionizes compounds exiting the GC column
The quadrupole filter allows ions of specific mass to pass through the filter and strike the ion collector.
The mass selectivity of the filter can be continuously scanned over a pre-determined range by changing the dc and rf settings of the filter.
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Innova AirTech Instruments Type 1312 Multi-gas Monitor
Description: Field-portable, photoacoustic infrared bandpass spectrometer
Size, Weight: Small, 30 pounds
Sample Handling: Partially automated
Sample Throughput: 1-2 samples/hr
Data Processing: Automated method, manual recording of data necessary, no printed report
Calibration: Factory calibration, no daily check standards
Power: Battery or AC
Cost: $28-35K
Accessories: Headspace flask, stir plate, tubing
Operator training: Several hours for a field technician
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Innova AirTech Instruments Type 1312 Multi-gas Monitor
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Photoacoustic Spectroscopy
Chopped (intermittent) bandpass-filtered infrared radiation is passed through a cell containing the gases of interest.
The target gases absorb the radiation. The absorption is accompanied by a rise and fall in temperature (pressure) in the cell at the chopping frequency.
This pressure cycle or acoustic signal is detected by two sensitive microphones. The intensity of the pressure cycle is related to the target gas concentration.
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Verification Test Design Elements
Different Environmental Conditions– Testing at two contaminated sites with groundwater wells (Savannah River, SC and McClellan AFB, CA) – Historical sampling data used to select GW wells
A Blend of Field and QA Samples– Performance evaluation (PE), 42 samples per site– Groundwater (GW), 33 samples per site– Blank samples, 8 per site
Reference Laboratory Analyses– Splits of all samples analyzed by an off-site reference
laboratory– US EPA Method 8260 (Purge-and-trap GC-MS)
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Verification Test Design Elements cont’d
PE Mix 1 - Purgeable ASupelco Cat. No. 4-8059
Lot LA68271
PE Mix 2 - VOC 3Supelco Cat. No. 4-8779
Lot LA64701
PE Mix 3 - Purgeable BSupelco Cat. No. 4-8058
Lot LA 63978
Trichlorofluoromethane 1,1-Dichloropropene 1,2-Dichloroethane
1,1-Dichloroethane 1,2-Dichloroethane 1,1,2,2-Tetrachloroethane
Dichloromethane Trichloroethene cis-1,3-Dichloropropene
1,1-Dichloroethene 1,2-Dichloropropane trans-1,3-Dichloropropene
Chloroform 1,1,2-Trichloroethane trans-1,2-Dichloroethene
Carbon tetrachloride 1,3-Dichloropropane 1,1,1-Trichloroethane
Trichloroethene 1,2-Dibromoethane Benzene
1,2-Dichloropropane 1,1,1,2-Tetrachloroethane Bromodichloromethane
1,1,2-Trichloroethane 1,1,2,2-Tetrachloroethane Toluene
Tetrachloroethene 1,2,3-Trichloropropane Ethyl benzene
Dibromochloromethane 1,2-Dibromo-3-chloropropane Bromoform
Chlorobenzene cis-1,3-Dichloropropene
1,2-Dichlorobenzene trans-1,3-Dichloropropene
2-Chloroethyl vinyl ether Hexachlorobutadiene
Multiple VOC Compounds
Participating technologies were not calibrated for all these compounds
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Verification Test Design Elements cont’d
A Wide Concentration Range of Compounds
– PE Samples: 10 µg/L to >1000 µg/L
– GW Samples: 5 µg/L to > 1000 µg/L
Blind Replicate Samples
– Triple or quadruplicate splits of all GW and PE samples
– for determination of instrument precision
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A Challenging Test Sample Matrix
A Challenging Test Sample Matrix
65 environmental groundwater samples from both sites
84 performance evaluation (PE) water samples mixed and distributed onsite
8 blank samples ~160 samples analyzed per
technology over ~ 8 days Over 9000 individual compound
analyses!
Groundwater
PE + Blanks
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Field Sample PreparationPE Samples Performance Evaluation samples were mixed in a 10-L carboy in an onsite mobile laboratory and then dispensed into 40-mL VOA vials Each of the five technologies and reference lab were given 4 replicates from all PE mixtures
GW Samples 10 liters of groundwater was sampled into a glass carboy from various monitoring wells with downhole electric pumps Carboy contents were mixed and then dispensed into 40-mL VOA vials at the wellhead. Replicate samples were distributed to all participants and the reference laboratory
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Sample Distribution
GW Samples
Blank Samples
PE SamplesHAPSITE
VOYAGER
Model 4100
Scentograph Plus II
Multi-gas Monitor
Reference Lab
Each sample delivered intriplicate or quadruplicate
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Definition of Terms
Precision Relative standard deviation from replicate samples
Accuracy Average percent recovery of a known test sample or absolute percent difference from a known
Comparability Percent difference of results relative to reference laboratory results
Detection Limit Method Detection Limit or Practical Quantitation Limit
Sample Samples per hour Throughput
False Positive Frequency that detects are reported for blank samples
False Negative Frequency that no-detects are reported for compounds at or near the 5 ug/L regulatory limit
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Key Instrument Performance Parameters in this Test
Accuracy - percent recovery
Precision - relative standard deviation
Comparability to reference - absolute percent difference
False positive/negative - at blank and 10 ug/L conc. levels
Sample throughput - samples per hour
Versatility - number of compounds detected
Ease of use - through field observation
Operator training requirements -through field
observation
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ETV doesn’t compare technologies
In a policy of fairness and
objectivity, ETV doesn’t pick
technology winners and losers
Technologies are varied and their
application is usually site- and
application-specific
The site user is best-suited to
match site needs with technology
capabilities
Side-by-side comparisons, if
required, are left to the user
Brand X Brand Y
???
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How the results are presented
Presentation by instrument
Performance CharacteristicsFalse +/-AccuracyPrecisionComparison with Reference Lab
Summarized results are necessary (lots of data in reports!) Performance for TCE and PCE is emphasized
TechnologyPerformanceResults
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Perkin Elmer Voyager False +/-
False positive rate in 16 blanks: 19%False negatives for SRS site (10 Samples at 10 g/L):
Compound False Negative Rate (%)1,1-Dichloroethene 0 Dichloromethane 0 Chloroform 100Carbon tetrachloride 0 1,2-Dichloropropane 80Trichloroethene 01,1,2-Trichloroethane 100Dibromochloromethane 90Tetrachloroethene 0 Chlorobenzene 0 1,1-Dichloroethane No calibration1,2-Dichlorobenzene No calibration
50
Voyager Summary Precision
% RSD VoyagerTCE
Ref LabTCE
VoyagerPCE
Ref LabPCE
Median 15 6 ** 6
Minimum 7 1 9 2
Maximum 71 12 ** 22
N SampleSets
8 16 8 11
Combined data from PE samples at both sites** Voyager did not detect PCE in 7 of 8 sets
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Average Voyager Recovery for Selected Compounds
0 50 100 150 200 250 300 350 400
TCE @ SRS
TCE @ MCL
PCE @ SRS
PCE @MCL
12DCA @ SRS
12DCA @ MCL
Co
mp
ou
nd
an
d S
ite
Average Percent Recovery
Low Conc. (~100 ug/L)
Mid Conc. (~200 ug/L)
High Conc. (~800 ug/L)
High/Low Mix Conc.
52
Voyager Summary Accuracy
Compound % RecoveryRange
Trichloroethene 92–344
1,2-Dichloroethane 34–170
1,2-Dichloropropane 34–170
1,1,2-Trichloroethane1,2-Dichloropropane
50–116
Tetrachloroethene 1–124
Trans-1,3-Dichloropropane
72–162
For selected target compounds
53
Scatter Plot Comparisons with Reference Lab
Example scatter plots shown for both sites combined A total of 20 TCE and 20 PCE detects by the reference
lab at all concentration ranges at both sites Only TCE and PCE results below 500 ug/L are plotted False negatives reported by technology are also shown Diagonal line in plot is the zero-bias line
54
Perkin Elmer Voyager vs. Lab Reference
TCE and PCE in groundwater samples at both sites
0
50
100
150
200
250
300
350
400
450
500
0 100 200 300 400 500
Ref Lab Conc. (ug/L)
Vo
ya
ge
r C
on
c. (
ug
/L)
TCE at SRS
TCE at MAFB
PCE at SRS
PCE at MAFB
0 False Negatives Reported
55
Perkin-Elmer, VoyagerPerformance Summary
False negative rate: low for TCE and PCE
Precision: <20% RSD for TCE
Undetermined for PCE
Accuracy: 90-340% TCE Recovery
1-120% PCE Recovery
Reference Lab Comparison: Biased high for TCE and PCE
56
Scentograph Plus II False +/-
Compound False Negative Rate (%)1,1-Dichloroethene 0Dichloromethane 0Carbon tetrachloride 0 1,2-Dichloropropane 30Trichloroethene 01,1,2-Trichloroethane 0 Tetrachloroethene 0 Chlorobenzene 0 2-Chloroethyl vinyl ether No calibrationDibromochloromethane No calibrationTrichlorofluoromethane No calibration1,1-Dichloroethane No calibration1,2-Dichlorobenzene No calibration
False positive rate in 16 blanks: 0%False negatives for SRS site (10 Samples at 10 g/L):
57
Scentograph II Summary Precision
% RSD ScentogrTCE
Ref LabTCE
ScentogrPCE
Ref LabPCE
Median 6 6 7 6
Minimum 0 1 3 2
Maximum 17 12 13 22
N SampleSets
8 16 4 11
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Average Scentograph Recovery for Selected Compounds
0 20 40 60 80 100 120 140 160 180 200
TCE @ SRS
TCE @ MCL
PCE @ SRS
PCE @MCL
12DCA @ SRS
12DCA @ MCL
Co
mp
ou
nd
an
d S
ite
Average Percent Recovery
Low Conc. (~100 ug/L)
Mid Conc. (~200 ug/L)
High Conc. (~800 ug/L)
High/Low Mix Conc.
59
Scentograph Plus II Summary Accuracy
Compound % RecoveryRange
Trichloroethene 76–117
1,2-Dichloroethane 103–178
1,2-Dichloropropane
84–122
1,1,2-Trichloroethane
85–116
Tetrachloroethene 96–115
trans-1,3-Dichloropropane
83–124
For selected target compounds
60
Sentex Scentograph Plus II vs. Lab Reference
0
50
100
150
200
250
300
350
400
450
500
0 100 200 300 400 500
Ref Lab Conc. (ug/L)
Sc
en
tog
rap
h C
on
c. (
ug
/L)
TCE at SRS
TCE at MAFB
PCE at SRS
PCE at MAFB
4 False Negatives Reported
TCE and PCE in groundwater samples at both sites
61
Sentex Scentograph Plus II
Performance Summary
False negative rate: low for TCE and PCE
Precision: <10% RSD for TCE
<10% RSD for PCE
Accuracy: 75-115% TCE Recovery
95-115% PCE Recovery
Reference Lab Comparison: No bias for TCE and PCE
62
EST Model 4100 II False +/-
Compound False Negative Rate (%)1,1-Dichloroethene 100Dichloromethane No calibrationChloroform 100Carbon tetrachloride 1001,2-Dichloropropane 100Trichloroethene 01,1,2-Trichloroethane 100Dibromochloromethane No calibrationTetrachloroethene 0Chlorobenzene 01,1-Dichloroethane 1001,2-Dichlorobenzene 100
False positive rate in 16 blanks: 0%False negatives for SRS site (10 Samples at 10 g/L):
63
Model 4100 Summary Precision
% RSD Model 4100TCE**
Ref LabTCE
Model 4100PCE
Ref LabPCE
Median 10 6 12 6
Minimum 2 1 6 2
Maximum 28 12 22 22
N SampleSets
8 16 6 11
**TCE reported as a co-eluter with 1,2 dichloropropane
64
Average Model 4100 Recovery for Selected Compounds
0 20 40 60 80 100 120 140 160 180 200
TCE @ SRS
TCE @ MCL
PCE @ SRS
PCE @MCL
112TCA @ SRS
112TCA @ MCL
Co
mp
ou
nd
an
d S
ite
Average Percent Recovery
Low Conc. (~100 ug/L)
Mid Conc. (~200 ug/L)
High Conc. (~800 ug/L)
High/Low Mix Conc.
65
Model 4100 Summary Accuracy
Compound % RecoveryRange
Trichloroethene 58–75
1,2-Dichloropropane 380–5038
1,2,3-Trichloropropane 49–174
1,1,2-Trichloroethane 57–118
Tetrachloroethene 34–68
trans-1,3-Dichloropropene
57–145
For selected target compounds
66
EST Model 4100 vs. Lab Reference
TCE and PCE in groundwater samples at both sites
0
50
100
150
200
250
300
350
400
450
500
0 100 200 300 400 500
Ref Lab Conc. (ug/L)
Mo
de
l 41
00
Co
nc
. (u
g/L
)
TCE at SRS
TCE at MAFB
PCE at SRS
PCE at MAFB
0 False Negatives Reported
67
EST Model 4100Performance Summary
False negative rate: low for TCE and PCE
Precision: <10% RSD for TCE
<20% RSD for PCE
Accuracy: 60-75% TCE Recovery
35-70% PCE Recovery
Reference Lab Comparison: Biased low for TCE and PCE
68
Inficon HAPSITE False +/-
Compound False Negative Rate (%)1,1-Dichloroethene 0Dichloromethane 01,1-Dichloroethane 0Chloroform 0Carbon tetrachloride 101,2-Dichloropropane 0Trichloroethene 01,1,2-Trichloroethane 40Dibromochloromethane 20Tetrachloroethene 40Chlorobenzene 101,2-Dichlorobenzene No calibration
False positive rate in 16 blanks: 25%False negatives for SRS site (10 Samples at 10 g/L):
69
HAPSITE Summary Precision
% RSD HAPSITETCE
Ref LabTCE
HAPSITEPCE
Ref LabPCE
Median 14 6 15 6
Minimum 7 1 6 2
Maximum 18 12 22 22
N SampleSets
8 16 6 11
70
Average HAPSITE Recovery for Selected Compounds
0 20 40 60 80 100 120 140 160 180 200
TCE @ SRS
TCE @ MCL
PCE @ SRS
PCE @MCL
12DCA @ SRS
12DCA @ MCL
Co
mp
ou
nd
an
d S
ite
Average Percent Recovery
Low Conc. (~100 ug/L)
Mid Conc. (~200 ug/L)
High Conc. (~800 ug/L)
High/Low Mix Conc.
71
HAPSITE Summary Accuracy
Compound % RecoveryRange
Trichloroethene 80–114
1,2-Dichloroethane 91–103
1,1,2-Trichloroethane 79–120
1,2-Dichloropropane 79–113
Tetrachloroethene 67–93
trans-1,3-Dichloropropane
85–101
For selected target compounds
72
Inficon HAPSITE vs. Lab Reference
0
50
100
150
200
250
300
350
400
450
500
0 100 200 300 400 500
Ref Lab Conc. (ug/L)
HA
PS
ITE
Co
nc
. (u
g/L
)
TCE at SRS
TCE at MAFB
PCE at SRS
PCE at MAFB
2 False Negatives Reported
TCE and PCE in groundwater samples at both sites
73
Inficon HAPSITEPerformance Summary
False negative rate: low for TCE, high for PCE
Precision: <15% RSD for TCE
<15% RSD for PCE
Accuracy: 80-115% TCE Recovery
70-95% PCE Recovery
Reference Lab Comparison: No bias for TCE and PCE
74
Innova Multi-gas Monitor False +/-
False positive rate in 16 blanks: 13%
False negatives for SRS site:(6 samples at 10 g/L, TCE and PCE only)
Compound False Negative Rate (%)
Trichloroethene 0Tetrachloroethene 50
75
Multi-gas Monitor Summary Precision
% RSD Multi-gasTCE
Ref LabTCE
Multi-gasPCE
Ref LabPCE
Median 16 6 13 6
Minimum 4 1 5 2
Maximum 22 12 46 22
N SampleSets
13 16 13 11
76
Average Multi-gas Monitor Recovery for TCE and PCE
0 20 40 60 80 100 120 140 160 180 200
TCE @ SRS
TCE @ MCL
PCE @ SRS
PCE @ MCL
Co
mp
ou
nd
an
d S
ite
Average Percent Recovery
Low 1 (~50 ug/L)
Low 2 (~100 ug/L)
Mid 1 (~200 ug/L)
Mid 2 (~250 ug/L)
High 1 (~400 ug/L)
High 2 (~700 ug/L)
VHigh (~1250 ug/L)
77
Multi-gas Monitor Summary Accuracy
Compound % RecoveryRange
Tetrachloroethene 52–107
Trichloroethene 52–111
For TCE and PCE
78
Innova Multi-gas Monitor vs. Lab Reference
TCE and PCE in groundwater samples at both sites
0
50
100
150
200
250
300
350
400
450
500
0 100 200 300 400 500
Ref Lab Conc. (ug/L)
Mu
lti-
ga
s M
on
ito
r C
on
c. (
ug
/L)
TCE at SRS
TCE at MAFB
PCE at SRS
PCE at MAFB
3 False Negatives Reported
79
Innova Multi-gas Monitor
Performance Summary
False negative rate: low for TCE, high for PCE
Precision: <20% RSD for TCE
<15% RSD for PCE
Accuracy: 50-110% TCE Recovery
50-110% PCE Recovery
Reference Lab Comparison: No bias for TCE and PCE
80
Perkin-Elmer, Voyager
Advantages Lightweight and small Sensitive and selective for a variety of VOCs Three columns and dual detectors (PID/ECD) can
help in the identification of unknown compounds Detects most VOCs, including halogenated and
non-halogenated aliphatic and aromatic hydrocarbons
Instrument is easy to operate
81
Perkin-Elmer, Voyager
Limitations EC detector requires radioactive permit/license Isothermal column only -- co-elution of analytes
possible in complex samples Somewhat cumbersome manual sample handling
and injection is required Equilibrium headspace method limits sensitivity for
some VOC compounds Equilibrium headspace method used in this test
needed further development and negatively influenced the results
82
Sentex Systems Inc., Scentograph Plus II
Advantages Purge-and-trap system with MAID offers high
sensitivity -- sub-ppb detection for most VOCs
Isothermal or temperature programmable operation
Dual detector option can give versatility:
– microargon ionization (MAID)
– electron capture detector (ECD)
Virtually no sample handling required
System could be fully automated to run unattended
83
Sentex Systems Inc., Scentograph Plus II
Limitations Maximum operating temperature of 179 o C
MAID and ECD detectors contain tritium and may require a state permit/license
At the time of the test, control and analysis software was dated and in need of an upgrade
Only moderately portable -- two bulky packages plus accessories
84
Electronic Sensor Technology Inc.,Model 4100
Advantages Compact portable package
Purge-and-trap feature enables improved detection levels over equilibrium headspace methods
Minimal sample handling requirements
Universal (mass sensitive) SAW detector
Wide detector dynamic range (greater than 104)
Fast throughput (less than 30-second chromatographic total elution time)
85
Limitations With fast analysis times, co-elution of
compounds is possible Data analysis for complex samples is not fully
automated and requires considerable operator intervention
Operator experience in chromatography desirable for complex samples
Electronic Sensor Technology Inc.Model 4100
86
Inficon, HAPSITE
Advantages Headspace accessory enables automatic GC
injection
Unknown compound identification with on-board mass spectral libraries
Highly versatile for unknown identification
Moderately portable (3 pieces including PC) in light of the analytical power of the instrument
87
Inficon, HAPSITE
Limitations Considerable sample handling is required
Isothermal operation only
Compound sensitivity is limited by equilibrium headspace considerations
Instrument is relatively expensive
Maintenance costs can be high (getter pump)
88
Innova AirTech Instruments Type 1312 Multi-gas Monitor
Advantages Detection limits for TCE and PCE in water are
in the low ppb range
Large dynamic range (6 orders of magnitude)
Small cell volume reduces volumes of samples and calibration gas
Instrument is easy to use
Calibrations are stable over many months
89
Innova AirTech Instruments Type 1312 Multi-gas Monitor
Limitations Some sample handling is required
The headspace flask accessory needs further development
Instrument must be factory calibrated for the compounds of interest
Compound sensitivity is limited by equilibrium headspace considerations
The presence of unknowns can cause erroneous results
90
ETV Site Characterization and Monitoring Technologies information is at the US EPA web site
www.epa.gov/etv
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For more information...
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Links to Additional Resources