EPA/600/R-98/145
November 1998
Environmental Technology Verification
Report
Field-Portable Gas Chromatograph
Sentex Systems, Inc. Scentograph Plus II
by
Wayne Einfeld
Sandia National Laboratories
Albuquerque, New Mexico 87185-0755
IAGDW89936700-01-0
Project Officer
Stephen Billets
National Exposure Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Las Vegas, Nevada 89193
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Notice
The U.S. Environmental Protection Agency (EPA), through its Office of Research and Development (ORD), funded
and managed, under Interagency Agreement No. DW89936700-01-1 with the U.S. Department of Energy's Sandia
National Laboratory, the verification effort described in this document. This report has received both technical peer
and administrative policy reviews and has been approved for publication as an EPA document. Mention of
corporate names, trade names, or commercial products does not constitute endorsement or recommendation for use.
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u
a
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, D.C. 20460
ENVIRONMENTAL TECHNOLOGY VERIFICATION PROGRAM
VERIFICATION STATEMENT
TECHNOLOGY TYPE:
APPLICATION:
TECHNOLOGY NAME:
COMPANY
ADDRESS:
PHONE:
FIELD-PORTABLE GAS CHROMATOGRAPH
MEASUREMENT OF CHLORINATED VOLATILE ORGANIC
COMPOUNDS IN WATER
Scentograph Plus II
Sentex Systems, Inc.
553 Broad Ave.
Ridgefield, NJ 07657
(201) 945-3694
PROGRAM DESCRIPTION
The U.S. Environmental Protection Agency (EPA) created the Environmental Technology Verification (ETV)
Program to facilitate the deployment of innovative environmental technologies through performance verification and
information dissemination. The goal of the ETV Program is to further environmental protection by substantially
accelerating the acceptance and use of improved and cost-effective technologies. The ETV Program is intended to
assist and inform those involved in the design, distribution, permitting, and purchase of environmental technologies.
Under this program, in partnership with recognized testing organizations, and with the full participation of the
technology developer, the EPA evaluates the performance of innovative technologies by developing demonstration
plans, conducting field tests, collecting and analyzing the demonstration results, and preparing reports. The testing
is conducted in accordance with rigorous quality assurance protocols to ensure that data of known and adequate
quality are generated and that the results are defensible. The EPA National Exposure Research Laboratory, in
cooperation with Sandia National Laboratories, the testing organization, evaluated field-portable systems for
monitoring chlorinated volatile organic compounds (VOCs) in water. This verification statement provides a
summary of the demonstration and results for the Sentex Systems, Inc. Scentograph Plus II, field-portable gas
chromatograph (GC).
DEMONSTRATION DESCRIPTION
The field demonstration of the Scentograph Plus II portable GC was held in September 1997. The demonstration
was designed to assess the ability of the instrument to detect and measure chlorinated VOCs in groundwater at two
contaminated sites: the Department of Energy's Savannah River Site, near Aiken, South Carolina, and the
McClellan Air Force Base, near Sacramento, California. Groundwater samples from each site were supplemented
with performance evaluation (PE) samples of known composition. Both sample types were used to assess
instrument accuracy, precision, sample throughput, and comparability to reference laboratory results. The primary
target compounds at the Savannah River Site were trichloroethene and tetrachloroethene. At McClellan Air Force
Base, the target compounds were trichloroethene, tetrachloroethene, 1,2-dichloroethane, 1,1,2-trichloroethane, 1,2-
EPA-VS-SCM-27
The accompanying notice is an integral part of this verification statement
iii
November 1998
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dichloropropane, and ?ra«s-l,3-dichloropropene. These sites were chosen because they contain varied
concentrations of chlorinated VOCs and exhibit different climatic and geological conditions. The conditions at these
sites are typical, but not inclusive, of those under which this technology would be expected to operate. A complete
description of the demonstration, including a data summary and discussion of results, may be found in the report
entitled Environmental Technology Verification Report, Field-Portable Gas Chromatograph, Sentex Systems,
Inc., Scentograph Plus II. (EPA/600/R-98/145).
TECHNOLOGY DESCRIPTION
Gas chromatography with electron capture detection is a proven analytical technology that has been used in
environmental laboratories for many years. The gas chromatographic column separates the sample into individual
components. The electron capture detector measures a change in electron current from a sealed radioactive source as
compounds exit the chromatographic column, move through the detector, and capture electrons. The electron
capture detector is particularly sensitive to chlorinated compounds. Compound identification is achieved by
matching the column retention time of sample components, run under controlled temperature conditions, to those of
standard mixtures run under similar conditions. Quantitation is achieved by comparing the detector response
intensity of sample component and standard. A GC offers some potential for identification of unknown components
in a mixture; however, a confirmational analysis by an alternative method is often advisable. Portable GC is a
versatile technique that can be used to provide rapid screening data or routine monitoring of groundwater samples.
In many GC systems, the instrument configuration can also be quickly changed to accommodate different sample
matrices such as soil, soil gas, water, or air. As with all field analytical studies, it may be necessary to send a
portion of the samples to an independent laboratory for confirmatory analyses.
The Scentograph Plus II consists of three modules: a purge-and-trap unit, a GC, and a notebook computer for
instrument control and data acquisition. The entire system weighs about 80 pounds and is about the size of a large
suitcase. The units can be easily transported and operated in the rear compartment of a minivan or station wagon.
Instrument detection levels for most chlorinated VOCs in water range from 0.1 to 50 ng/L. Sample processing and
analysis can be accomplished by a chemical technician; however, instrument method development, instrument
calibration, and data processing require a higher level of operator experience and training. The recommended
training interval for routine sample processing is 1 day for a field technician with limited GC experience. At the time
of the demonstration, the baseline cost of the Scentograph Plus II was $35,000. Operational costs, which take into
account consumable supplies, are on the order of $25 per 8-hour day.
VERIFICATION OF PERFORMANCE
The following performance characteristics of the Scentograph Plus II were observed:
Sample Throughput: Throughput was about two samples per hour. This rate includes the periodic analysis of
blanks and calibration check samples. The sample throughput rate is influenced by the complexity of the sample,
with less complex samples yielding higher throughput rates.
Completeness: The Scentograph Plus II reported results for all 165 PE evaluation and groundwater samples
provided for analysis at the two demonstration sites.
Analytical Versatility: The Scentograph Plus II was calibrated for and detected 59% (19 of 32) of the PE sample
VOC compounds in the PE samples provided for analysis at the demonstration. Three pairs of coeluting compounds
were encountered with the GC methods used during this demonstration. For the groundwater contaminant
compounds for which it was calibrated, the Scentograph Plus II detected 35 of the 62 compounds reported by the
reference laboratory at concentration levels in excess of 1 ng/L. A total of 68 compounds were detected by the
reference laboratory in all groundwater samples.
Precision: Precision was determined by analyzing sets of four replicate samples from a variety of PE mixtures
containing known concentrations of chlorinated VOCs. The results are reported in terms of relative standard
deviations (RSD). The RSDs compiled for all reported compounds from both sites had a median value of 8% and a
EPA-VS-SCM-27 The accompanying notice is an integral part of this verification statement November 1998
iv
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95th percentile value of 32%. By comparison, the compiled RSDs from the reference laboratory had a median value
of 7% and a 95th percentile value of 25%. The ranges of Scentograph Plus II RSD values for specific target
compounds were as follows: trichloroethene, 0 to 17%; tetrachloroethene, 3 to 28%; 1,2-dichloropropane, 5 to
12%; 1,1,2-trichloroethane, 6 to 24%; ?ra«s-l,3-dichloropropene, 4 to 29%; and 1,2-dichloroethane, 6 to 36%.
Accuracy: Instrument accuracy was evaluated by comparing Scentograph Plus II results with the known
concentrations of chlorinated VOCs in PE mixtures. Absolute percent difference (APD) values from both sites were
calculated for all reported compounds in the PE mixtures. The APDs from both sites had a median value of 10% and
a 95th percentile value of 38%. By comparison, the compiled APDs from the reference laboratory had a median
value of 7% and a 95th percentile value of 24%. The ranges of Scentograph Plus II APD values for target
compounds were as follows: trichloroethene, 1 to 24%; tetrachloroethene, 0 to 15%; 1,2-dichloropropane, 2 to 22%;
1,1,2-trichloroethane, 3 to 16%; ?ra«s-l,3-dichloropropene, 0 to 24%; and 1,2-dichloroethane, 3 to 78%.
Comparability: A comparison of Scentograph Plus II and reference laboratory data was based on 33 groundwater
samples analyzed at each site. The correlation coefficient (r) for all compounds detected by both the Scentograph
Plus II and laboratory at or below the 100 ng/L concentration level was 0.974 at Savannah River and 0.959 at
McClellan. The r values for compounds detected at concentration levels in excess of 100 ng/L were 0.907 for
Savannah River and 0.997 for McClellan. These correlation coefficients reveal a highly linear relationship between
Scentograph Plus II and laboratory data. The median APD between groundwater compounds mutually detected by
the Scentograph Plus II and the reference laboratory was 12% with a 95th percentile value of 194%.
Deployment: The system was ready to analyze samples within 60 minutes of arrival at the site. At both sites, the
instrument was transported in a minivan and operated from its folded middle seat. The instrument was powered by
line ac or from a small dc-to-ac inverter connected to the vehicle's battery.
The results of the demonstration show that the Sentex Systems, Inc., Scentograph Plus II field-portable GC with
electron capture detector can provide useful, cost-effective data for environmental site screening and routine
monitoring. This instrument could be employed in a variety of applications, ranging from producing rapid analytical
results in screening investigations, to producing accurate and precise data that are directly comparable with that
obtained from an off-site laboratory. These data could be used to develop risk assessment information, support a
remediation process, or fulfill monitoring requirements. In the selection of a technology for deployment at a site, the
user must determine what is appropriate through consideration of instrument performance and the project's data
quality objectives.
Gary J. Foley, Ph. D.
Director
National Exposure Research Laboratory
Office of Research and Development
Samuel G. Varnado
Director
Energy and Critical Infrastructure Center
Sandia National Laboratories
NOTICE: EPA verifications are based on an evaluation of technology performance under specific, predetermined criteria
and the appropriate quality assurance procedures. EPA makes no expressed or implied warranties as to the performance of
the technology and does not certify that a technology will always, under circumstances other than those tested, operate at
the levels verified. The end user is solely responsible for complying with any and all applicable federal, state and local
requirements.
EPA-VS-SCM-27
The accompanying notice is an integral part of this verification statement
V
November 1998
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Foreword
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the nation's natural
resources. The National Exposure Research Laboratory (NERL) is the EPA center for the investigation of
technical and management approaches for identifying and quantifying risks to human health and the environment.
The NERL research goals are to (1) develop and evaluate technologies for the characterization and monitoring of
air, soil, and water; (2) support regulatory and policy decisions; and (3) provide the science support needed to
ensure effective implementation of environmental regulations and strategies.
The EPA created the Environmental Technology Verification (ETV) Program to facilitate the deployment of
innovative technologies through verification of performance and dissemination of information. The goal of the ETV
Program is to further environmental protection by substantially accelerating the acceptance and use of improved
and cost-effective technologies. It is intended to assist and inform those involved in the design, distribution,
permitting, and purchase of environmental technologies.
Candidate technologies for this program originate from the private sector and must be market ready. Through the
ETV Program, developers are given the opportunity to conduct rigorous demonstrations of their technologies under
realistic field conditions. By completing the evaluation and distributing the results, the EPA establishes a baseline
for acceptance and use of these technologies.
Gary J. Foley, Ph. D.
Director
National Exposure Research Laboratory
Office of Research and Development
VI
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Executive Summary
The U.S. Environmental Protection Agency, through the Environmental Technology Verification Program, is
working to accelerate the acceptance and use of innovative technologies that improve the way the United States
manages its environmental problems. As part of this program, the Consortium for Site Characterization
Technology was established as a pilot program to test and verify field monitoring and site characterization
technologies. The Consortium is a partnership involving the U.S. Environmental Protection Agency, the
Department of Defense, and the Department of Energy. In 1997 the Consortium conducted a demonstration of five
technologies designed for the analysis of chlorinated volatile organic compounds in groundwater. The developers
participating in this demonstration were: Electronic Sensor Technology, Perkin Elmer-Photovac, and Sentex
Systems, Inc. (field-portable gas chromatographs); Innova AirTech Instruments (photoacoustic infrared analyzer);
and Inficon, Inc. (field-portable gas chromatograph/mass spectrometer). This report documents demonstration
activities, presents demonstration data, and verifies the performance of the Sentex Scentograph Plus II field-
portable gas chromatograph. Reports documenting the performance of the other technologies have been published
separately.
The demonstration was conducted at two geologically and climatologically different sites: the U.S. Department of
Energy's Savannah River Site, near Aiken South Carolina and McClellan Air Force Base, near Sacramento
California. Both sites have groundwater resources that are significantly contaminated with a variety of chlorinated
volatile organic compounds. The demonstrations designed to evaluate the capabilities of each field-transportable
system were conducted in September 1997 and were coordinated by Sandia National Laboratories.
The demonstration provided adequate analytical and operational data with which to evaluate the performance of the
Scentograph Plus II gas chromatograph. Instrument precision and accuracy were determined by an analysis of
replicate samples from 16 multicomponent standard mixtures of known composition. The relative standard
deviations, obtained from an analysis of 4 replicate samples from each of the 16 standard mixtures, were used as
measures of precision. The relative standard deviations from all compounds had a median value of 8% and a 95th
percentile value of 32%. Accuracy was expressed as the absolute percent difference between the Scentograph Plus
II measured value and the true value component in the standard mixtures. The distribution of absolute percent
differences for all reported compounds had a median value of 10% and a 95th percentile value of 38%. A
comparison of Scentograph Plus II and reference laboratory results from 33 groundwater samples at each site
resulted in a median absolute percent difference of 12% with a 95th percentile value of 194%. A correlation
analysis between Scentograph Plus II and laboratory results resulted in correlation coefficients (r) greater than 0.96
at low (<100 |o,g/L) contaminant concentrations. Correlation coefficients were greater than 0.91 at high (>100 jo,
g/L) contaminant concentrations. The sample throughput rate of the Scentograph Plus II was determined to be two
samples per hour. The Scentograph Plus II costs about $35,000 for a single-detector, single-column configuration,
and can be operated by a field technician with minimal training in gas chromatography.
Under appropriate applications, the Scentograph Plus II can provide useful, cost-effective data for environmental
site characterization and routine monitoring. As with any technology selection, the user must determine whether the
technology is appropriate for the application by taking into account instrument performance and the project's data
quality objectives.
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Vlll
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Contents
Notice ii
Verification Statement iii
Foreword vi
Executive Summary vii
Figures xiii
Tables xiv
Acronyms and Abbreviations xv
Acknowledgments xvii
Chapter 1 Introduction 1
Site Characterization Technology Challenge 1
Technology Verification Process 2
Identification of Needs and Selection of Technology 2
Planning and Implementation of Demonstration 2
Preparation of Report 3
Distribution of Information 3
The Wellhead VOC Monitoring Demonstration 3
Chapter 2 Technology Description 5
Technology Overview 5
Principle of Operation 6
Instrument Description 6
Operational Mode 6
Detector Systems 7
Sample Injection 8
History of the Technology 8
Applications 9
Advantages 9
IX
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Limitations 9
Performance Characteristics 9
Method Detection Limits 9
Practical Quantitation Limit 9
Accuracy 10
Precision 10
Instrument Working Range 10
Comparison with Reference Laboratory Analyses 10
Data Completeness 10
Specificity 10
Other Field Performance Characteristics 11
Instrument Setup and Disassembly Time 11
Instrument Calibration Frequency 11
Ancillary Equipment Requirements 11
Field Maintenance Requirements 11
Sample Throughput Rate 11
Ease of Operation 11
Chapter 3 Demonstration Design and Description 12
Introduction 12
Overview of Demonstration Design 12
Quantitative Factors 12
Qualitative Factors 13
Site Selection and Description 14
Savannah River Site 14
McClellan Air Force Base 16
Sample Set Descriptions 18
PE Samples and Preparation Methods 21
Groundwater Samples and Collection Methods 23
Sample Handling and Distribution 23
Field Demonstration Schedule and Operations 24
Site Operations and Environmental Conditions 24
Field Audits 25
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Data Collection and Analysis 26
Demonstration Plan Deviations 26
Chapter 4 Laboratory Data Results and Evaluation 27
Introduction 27
Reference Laboratory 27
Laboratory Selection Criteria 27
Summary of Analytical Work by DataChem Laboratories 28
Summary of Method 8260A 28
Method 8260A Quality Control Requirements 28
Summary of Laboratory QC Performance 28
Target Compound List and Method Detection Limits 29
Sample Holding Conditions and Times 29
System Calibration 29
Daily Instrument Performance Checks 31
Batch-Specific Instrument QC Checks 31
Sample-Specific QC Checks 31
Summary of Analytical and QC Deviations 33
Other Data Quality Indicators 33
PE Sample Precision 34
PE Sample Accuracy 34
Groundwater Sample Precision 39
Summary of Reference Laboratory Data Quality 40
Chapter 5 Demonstration Results 41
Scentograph Plus II Calibrated and Reported Compounds 41
Preanalysis Sample Information 41
Sample Completion 42
Blank Sample Results 42
Performance at Method Detection Limit 42
PE Sample Precision 42
PE Sample Accuracy 45
XI
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Comparison with Laboratory Results 46
Sample Throughput 52
Performance Summary 52
Chapter 6 Field Observations and Cost Summary 54
Introduction 54
Method Summary 54
Equipment 55
Sample Preparation and Handling 55
Consumables 55
Historical Use 55
Equipment Cost 55
Operators and Training 56
Data Processing and Output 56
Compounds Detected 56
Initial and Daily Calibration 57
QC Procedures and Corrective Actions 57
Sample Throughput 57
Problems Observed During Audit 57
Data Availability and Changes 57
Applications Assessment 58
Chapter 7 Technology Update 59
Comments on Demonstration Design 59
Additional Comments on Gas Chromatograph Performance 59
Chapter 8 Previous Deployments 61
References 63
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Figures
3-1. The general location of the Savannah River Site in the southeast United States 14
3-2. A map of the A/M area at the Savannah River Site showing the subsurface TCE plume 15
3 -3. A map of Sacramento and vicinity showing the location of McClellan Air Force Base 17
3 -4. Subsurface TCE plumes at McClellan Air Force Base in the shallowest (A) aquifer layer 19
4-1. Laboratory control standard recovery values for SRS analyses 32
4-2. Laboratory control standard recovery values for MAFB analyses 32
4-3. Laboratory precision on SRS PE samples containing mix 1 35
4-4. Laboratory precision on SRS PE samples containing mix 2 35
4-5. Laboratory precision on MAFB PE samples containing mix 2 36
4-6. Laboratory precision on MAFB PE samples containing mix 3 36
4-7. Laboratory mean recoveries for SRS PE samples containing mix 1 37
4-8. Laboratory mean recoveries for SRS PE samples containing mix 2 37
4-9. Laboratory mean recoveries for MAFB PE samples containing mix 2 38
4-10. Laboratory mean recoveries for MAFB PE samples containing mix 3 38
5-1. Scentograph Plus II precision on PE mix 1 at the SRS 43
5-2. Scentograph Plus II precision on PE mix 2 at the SRS 43
5-3. Scentograph Plus II precision on PE mix 2 at MAFB 44
5-4. Scentograph Plus II precision on PE mix 3 at MAFB 44
5-5. Scentograph Plus II recovery on PE mix 1 at the SRS 47
5-6. Scentograph Plus II recovery on PE mix 2 at the SRS 47
5-7. Scentograph Plus II recovery on PE mix 2 at MAFB 48
5-8. Scentograph Plus II recovery on PE mix 3 at MAFB 48
5 -9. Scentograph Plus II groundwater results at the SRS relative to laboratory results 51
5-10. Scentograph Plus II groundwater results at MAFB relative to laboratory results 51
6-1. The Scentograph Plus II GC 54
xin
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Tables
2-1. Scentograph Plus II Method Detection Limits for Selected VOCs in Water 10
3-1. Quarterly Monitoring Results for SRS Wells Sampled in the Demonstration 16
3-2. Groundwater Contaminants at MAFB 20
3-3. Quarterly Monitoring Results for MAFB Wells Sampled in the Demonstration 20
3 -3. Quarterly Monitoring Results for MAFB Wells Sampled in the Demonstration (Continued) 21
3-4. Composition of PE Source Materials 22
3-5. PE Sample Composition and Count for SRS Demonstration 22
3-6. Sample Composition and Count for MAFB Demonstration 23
3-7. Weather Summary for SRS and MAFB During Demonstration Periods 25
4-1. Method 8260A Quality Control Summary 29
4-2. Reference Laboratory Method Detection Limits for Target Compounds 30
4-3. Summary of Reference Laboratory Quality Control and Analytical Deviations 33
4-4. Sources of Uncertainty in PE Sample Preparation 34
4-5. Summary of SRS Groundwater Analysis Precision 39
4-6. Summary of MAFB Groundwater Analysis Precision 39
5-1. Scentograph Plus II Calibrated and Reported Compounds 41
5-2. False Negative Rates from Very Low-Level PE Sample Analysis 42
5-3. Target Compound Precision for PE Samples at Both Sites 45
5 -4. Summary PE Sample Precision and Percent Difference Statistics for the SRS and MAFB 46
5-5. Scentograph Plus II Target Compound Recovery for PE Mix 2 at Both Sites 49
5 -6. Scentograph Plus II and Reference Laboratory Results for SRS Groundwater Samples 49
5 -7. Scentograph Plus II and Reference Laboratory Results for MAFB Groundwater Samples 50
5-8. Scentograph Plus II Absolute Percent Difference Summary for Pooled Groundwater Results 52
5-9. Correlation Coefficients for Laboratory and Scentograph Plus II Groundwater Analyses 52
5-10. Scentograph Plus II Performance Summary 53
6-1. Scentograph Plus II Cost Summary 56
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Acronyms and Abbreviations
ac
Ah
Ar
APD
BNZN
°C
cc
ccc
CCL4
Cl
CLFRM
dc
11DCA
12DCA
DCE
11DCE
c!2DCE
112DCE
DCL
DOE
BCD
EPA
ETV
e
eV
GC
GW
GC/MS
He
3H
Hz
i.d.
L
m
mg
mg/L
alternating current
ampere hour
argon
absolute percent difference
benzene
degrees centigrade
cubic centimeters
calibration check compounds
carbon tetrachloride
chlorine
chloroform
direct current
1,1 -dichloroethane
1,2-dichloroethane
dichloroethene
1,1-dichloroethene
cis-1,2-dichloroethene
trans-1,2-dichloroethene
DataChem Laboratories
Department of Energy
electron capture detector
Environmental Protection Agency
Environmental Technology Verification (Program)
electron
electron-volt
gas chromatograph
groundwater
gas chromatograph/mass spectrometer
helium
tritium
hertz, cycles per second
inside diameter
liter
meter
milligram
milligrams per liter
xv
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mL
mm
MAFB
MAID
MCL
MDL
MS
NA
ND
NERL
ng/L
NIST
NR
PC
PCE
PE
PID
ppb
ppm
PQL
PVC
QA
QC
R
r
RPD
RSD
SPCC
SRS
TCA
111TCA
TCE
TCD
V
Vac
VGA
VOC
MS
jam
milliliter
millimeter
McClellan Air Force Base
microargon ionization detector
maximum concentration level
method detection limit
mass spectroscopy
not available
not detected
National Exposure Research Laboratory
nanograms per liter
National Institute of Standards and Technology
not reported
personal computer
tetrachloroethene (perchloroethene)
performance evaluation
photoionization detector
parts per billion
parts per million
practical quantitation limit
poly (vinyl chloride)
quality assurance
quality control
organic molecule
correlation coefficient
relative percent difference
relative standard deviation
system performance check compounds
Savannah River Site
trichloroethane
1,1,1 -trichloroethane
trichloroethene
thermal conductivity detector
volts
volts alternating current
volatile organics analysis
volatile organic compound
microgram
micrograms per liter
microliter
micrometer
xvi
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Acknowledgments
The author wishes to acknowledge the support of all those who helped plan and conduct the demonstrations,
analyze the data, and prepare this report. In particular, the technical expertise of Gary Brown, Robert Helgesen,
Michael Hightower, and Dr. Brian Rutherford of Sandia National Laboratories in the planning and conduct of the
study are recognized. The assistance of Dr. Timothy Jarosch and Joseph Rossabi of Savannah River
Westinghouse in demonstration planning and field activities at both Savannah River and McClellan is also
recognized. The willingness of Phillip Mook and Timothy Chapman of the Environmental Directorate at McClellan
Air Force Base to host the McClellan phase of the study is also greatly appreciated. The availability of funding
from the Strategic Environmental Research and Development Program helped to make the McClellan phase of the
study possible. The guidance and contributions of project technical leaders, Dr. Stephen Billets and Eric Koglin of
the EPA National Exposure Research Laboratory, Environmental Sciences Division in Las Vegas, Nevada, during
all phases of the project are also recognized.
The participation of personnel from Sentex Systems, Inc., in this technology demonstration is also acknowledged.
Marie Velasco operated the instrument during the demonstrations. Dr. Amos Linenberg provided setup and
calibration assistance. Additional technical support was provided by George Matta at Savannah River and by
Perry Dillon and Walter Mederas at McClellan.
For more information on the wellhead monitoring demonstration, contact:
Stephen Billets, Project Technical Leader, U.S. Environmental Protection Agency
National Exposure Research Laboratory, Environmental Sciences Division
P.O. Box 93478, Las Vegas, Nevada 89193-3478
(702) 798-2232
For more information on the Sentex Scentograph Plus II gas chromotograph, contact:
Dr. Amos Linenberg, Sentex Systems, Inc.
533 Broad Avenue, Ridgefield, NJ 07657
(201) 945-3694
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Chapter 1
Introduction
Site Characterization Technology Challenge
The U.S. Environmental Protection Agency (EPA) created the Environmental Technology Verification (ETV)
Program to facilitate the deployment of innovative environmental technologies through verification of performance
and dissemination of information. The goal of the ETV Program is to further environmental protection by
substantially accelerating the acceptance and use of improved and cost-effective technologies. It is intended to
assist and inform those involved in the design, distribution, permitting, purchase, and use of environmental
technologies. The ETV Program capitalizes on and applies the lessons that were learned in the implementation of
the Superfund Innovative Technology Evaluation Program to twelve pilot programs: Drinking Water Systems,
Pollution Prevention for Waste Treatment, Pollution Prevention for Innovative Coatings and Coatings Equipment,
Indoor Air Products, Advanced Monitoring Systems, EvTEC (an independent, private-sector approach), Wet
Weather Flows Technologies, Pollution Prevention for Metal Finishing, Source Water Protection Technologies, Site
Characterization and Monitoring Technology, Climate Change Technologies, and Air Pollution Control.
For each pilot, the EPA utilizes the expertise of partner "verification organizations" to design efficient procedures
for performance tests of the technologies. The EPA selects its partners from both public and private sectors,
including federal laboratories, states, and private sector entities. Verification organizations oversee and report
activities based on testing and quality assurance protocols developed with input from all major stakeholder and
customer groups associated with the technology area. The U.S. Department of Energy's (DOE's) Sandia National
Laboratories in Albuquerque, New Mexico, served as the verification organization for the demonstration described
in this report.
The performance verification reported here is based on data collected during a demonstration of technologies for the
characterization and monitoring of chlorinated volatile organic compounds (VOCs) in groundwater. Rapid,
reliable, and cost-effective field screening and analysis technologies are needed to assist in the complex task of
characterizing and monitoring hazardous and chemical waste sites. Environmental regulators and site managers are
often reluctant to use new technologies that have not been validated in an objective EPA-sanctioned testing program
or other similar process. Until the field performance of a technology can be verified through objective evaluations,
users will remain skeptical of innovative technologies, despite the promise of better, less expensive, and faster
environmental analyses. This demonstration was administered by the Site Characterization and Monitoring
Technology Pilot Program, which is also known as the Consortium for Site Characterization Technology. The
mission of the Consortium is to identify, demonstrate, and verify the performance of innovative site characterization
and monitoring technologies. The Consortium also disseminates information about technology performance to
developers, environmental remediation site managers, consulting engineers, and regulators.
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Technology Verification Process
The technology verification process consists of the four key steps shown here and discussed in more detail in the
following paragraphs:
1. identification of needs and selection of technology;
2. planning and implementation of demonstration;
3. preparation of report; and
4. distribution of information.
Identification of Needs and Selection of Technology
The first aspect of the verification process is to determine the technology needs of the EPA and the regulated
community. The EPA, the U.S. Department of Energy, the U.S. Department of Defense, industry, and state
agencies are asked to identify technology needs for site characterization and monitoring. Once a need is recognized,
a search is conducted to identify suitable technologies that will address this need. This search and identification
process consists of reviewing responses to Commerce Business Daily announcements, searching industry and trade
publications, attending related conferences, and following up on suggestions from technology developers and
experts in the field. Candidate characterization and monitoring technologies are evaluated against the following
criteria:
may be used in the field or in a mobile laboratory;
has a regulatory application;
is applicable to a variety of environmentally affected sites;
has a high potential for resolving problems for which current methods are unsatisfactory;
has costs that are competitive with current methods;
has performance as good or better than current methods in areas such as data quality, sample preparation, and/or
analytical turnaround time;
uses techniques that are easier and safer than current methods; and
is a commercially available, field-ready technology.
Planning and Implementation of Demonstration
After a technology has been selected, the EPA, the verification organization, and the developer(s) agree on a
strategy for conducting the demonstration and evaluating the technology. A conceptual plan for designing a
demonstration for a site characterization technology has been published by the Site Characterization and
Monitoring Technology Pilot Program (EPA, 1996a). During the planning process, the following steps are carried
out:
identification of at least two demonstration sites that will provide the appropriate physical or chemical attributes
in the desired environmental media;
identification and definition of the roles of demonstration participants, observers, and reviewers;
determination of logistical and support requirements (for example, field equipment, power and water sources,
mobile laboratory, communications network);
arranging for field sampling and reference analytical laboratory support; and
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preparation and implementation of a demonstration plan that addresses the experimental design, sampling design,
quality assurance and quality control (QA/QC), health and safety considerations, scheduling of field and
laboratory operations, data analysis procedures, and reporting requirements.
Preparation of Report
Each of the innovative technologies is evaluated independently and, when possible, against a reference technology.
The technologies are operated in the field by the developers in the presence of independent observers who are
provided by the EPA or the verification organization. Demonstration data are used to evaluate the capabilities,
limitations, and field applications of each technology. Following the demonstration, all raw and reduced data used
to evaluate each technology are compiled in a technology evaluation report, which is a record of the demonstration.
A data summary and detailed evaluation of each technology are published in an environmental technology
verification report. The report includes a verification statement, which is a concise summary of the instrument's
performance during the demonstration.
Distribution of Information
The goal of the information distribution strategy is to ensure that environmental technology verification reports and
accompanying verification statements are readily available to interested parties through traditional data distribution
pathways, such as printed documents. Related documents and updates are also available on the World Wide Web
through the ETV Web site (http://www.epa.gov/etv) and through a Web site supported by the EPA Office of Solid
Waste and Emergency Response Technology Innovation Office (http://clu-in.com). Additional information at the
ETV Web site includes a summary of the demonstration plan, test protocols (where applicable), demonstration
schedule and participants, and in some cases a brief narrative and pictorial summary of the demonstrations.
The Wellhead VOC Monitoring Demonstration
In August 1996, the selection of a technology for monitoring chlorinated VOCs in water was initiated by
publication in the Commerce Business Daily of a solicitation and notice of intent to conduct such a technology
demonstration. Potential participants were also solicited through manufacturer and technical literature references.
The original demonstration scope was limited to market-ready in situ technologies; however, only a limited response
was obtained, so the demonstration scope was expanded to include technologies that could be used to measure
groundwater at or near the wellhead. The final selection of technologies was based on the readiness of the
technologies for field demonstration and their applicability to the measurement of chlorinated VOCs in groundwater
at environmentally affected sites.
For this demonstration, five instrument systems were selected. Three of them were field-portable gas
chromatographs with various detection systems: one with a surface acoustic wave detector from Electronic Sensor
Technology, one with dual electron capture and photoionization detectors from Perkin-Elmer Photovac, and one
with an argon ion/electron capture detector from Sentex Systems. The fourth instrument was a field-portable gas
chromatograph/mass spectrometer (GC/MS) from Inficon, and the fifth was a photoacoustic infrared spectrometer
from Innova AirTech Instruments. This report documents demonstration activities, presents demonstration data,
and verifies the performance of the Sentex Systems Scentograph Plus II field-portable gas chromatograph. Reports
documenting the performance of other technologies have been published separately.
The demonstration was conducted in September 1997 at the DOE Savannah River Site (SRS) near Aiken, Georgia,
and at McClellan Air Force Base (MAFB), near Sacramento, California. Both sites have subsurface plumes of
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chlorinated VOCs and extensive networks of ground-water monitoring wells. The demonstrations were coordinated
by Sandia National Laboratories with the assistance of personnel from the Savannah River Site.
The primary objective of this demonstration was to evaluate and verify the performance of field-portable
characterization and monitoring technologies for analysis of chlorinated VOCs in groundwater. Specific
demonstration objectives were to:
verify instrument performance characteristics that can be directly quantified (such factors include response to
blank samples, measurement accuracy and precision, sample throughput, and data completeness);
verify instrument characteristics and performance in various qualitative categories such as ease of operation,
required logistical support, operator training requirements, transportability, versatility, and other related
characteristics; and
compare instrument performance with results from standard laboratory analytical techniques currently used to
analyze groundwater for chlorinated VOCs.
The goal of this and other ETV demonstrations is to verify the performance of each instrument as a separate entity.
Technologies are not compared with each other in this program. The demonstration results are summarized for
each technology independent of other participating technologies. In this demonstration, the capabilities of the five
instruments varied and in many cases were not directly comparable. Some of the instruments are best suited for
routine monitoring where compounds of concern are known and there is a maximum contaminant concentration
requirement for routine monitoring to determine regulatory compliance. Other instruments are best suited for
characterization or field-screening activities where groundwater samples of unknown composition can be analyzed
in the field to develop an improved understanding of the type of contamination at a particular site. This field
demonstration was designed so that both monitoring and characterization technologies could be verified.
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Chapter 2
Technology Description
This chapter was provided by the developer and was edited for format and relevance. The data presented include
performance claims that may not have been verified as part of the demonstration. Chapters 5 and 6 report
instrument features and performance observed in this demonstration. Publication of this material does not
represent EPA approval or endorsement.
Technology Overview
The Sentex Systems, Inc. Scentograph Plus II is a computer-controlled, field-portable gas chromatograph (GC)
designed to provide complete sample analysis, from calibration to interpretation of results. The technology is based
on purge-and-trap sample introduction, using a continuous purge-and-trap module in combination with the
Scentograph Plus II gas chromatograph. The Scentograph Plus II automatically performs the following functions:
calibration
analysis
sample collection and injection
chromatographic separation
compound detection
peak identification and integration
data display and storage, including chromatograms, retention times, concentration levels, and operating conditions
continuous operation
recalibration at predefined frequencies
optional remote operation via modem
The instrument consists of a GC module and a detector module. The GC module includes the oven, columns, and
detector(s). Packed columns 3 mm in diameter and up to 3 m in length or capillary columns with 0.53-mm i.d. and
up to 105 m in length are available. Two columns can be installed in the oven, whose temperature can be adjusted
up to 179 °C. The detectors are mounted in a compartment in the oven and heated to operating temperature. The
oven is well insulated and maintains the temperature of the column, the on-column injector, and the detector(s). For
optimum compound separation, two-stage temperature ramping is available. In this demonstration, a single-
column, single-detector configuration was used.
The Scentograph Plus II can be equipped with a variety of detectors, including electron capture (BCD), microargon
ionization (MAID), photoionization, and thermal conductivity. In this demonstration an electron
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capture detector was used. Both a microargon ionization detector and an electron capture detector are included in
one module. Changing from one detection mode to the other is accomplished by electronic switches. This
combined detector module is especially suitable for operation with capillary columns, and has the following
sensitivity:
MAID mode: sub-parts-per-billion (ppb, |Jg/L) levels of volatile hydrocarbons (e.g., benzene, toluene)
BCD mode: parts-per-trillion (ppt, ng/L) levels of chlorinated hydrocarbons (e.g., carbon tetrachloride,
trichloroethene)
Principle of Operation
Volatile organic compounds in water can be analyzed with the Scentograph Plus II by use of an accessory known as
the Aquascan, a continuous purge-and-trap device. This module is a fully computerized sampling system that
automates the steps required for purge-and-trap analysis of water samples. The operator connects the system
tubing and electrical cables and programs appropriate operating parameters. In the Aquascan, samples are
automatically drawn into a 10-mL cell and sparged with a carrier gas. The purged vapors are separated by the gas
chromatograph and detected by the MAID or BCD. The results and operating conditions are stored in memory for
later recall and review.
The purge-and-trap GC method is used to detect low concentrations of VOCs in water. In most cases,
concentrations will range from sub-parts-per-billion levels to hundreds of parts per billion. Higher concentrations
(i.e., above 200 ppb) are normally detected using headspace analysis by syringe injection of the headspace or by
trapping headspace volumes directly.
The purge-and-trap methodology efficiently removes the VOCs from the solution by purging with an inert carrier
gas. The VOCs are then carried to a sorbent material (usually Tenax or Carboxen). The adsorbed VOCs are
thermally desorbed onto the analytical column for separation. In routine operation, detection is usually
accomplished with a microargon ionization detector. The method identifies and measures extremely low levels of
VOCs, which are normally undetectable by other methods. Because low levels of VOCs in water may not generally
provide sufficient detectable concentrations of vapors when analyzed directly, the purge-and-trap method provides a
sample enrichment factor that brings the VOCs into a detectable quantitative range. Higher concentrations of
VOCs in the parts-per-million (ppm) range may also be analyzed; however, sample dilution to obtain a
concentration within the working range of the instrument may be necessary.
Instrument Description
Operational Mode
The Scentograph Plus II functions in calibration and sample analysis modes. In the calibration mode, a water
sample with known VOC composition is introduced into the Scentograph Plus II for chromatographic separation.
The software then displays the resulting chromatogram, including the name, concentration level, and retention time
of each compound in the calibration mixture. The area under each peak is integrated and the concentration level of
the standard is assigned to this peak area. Automatic multipoint calibration is also available.
The instrument is equipped with an internal calibration cylinder that supplies gas directly to the calibration system.
Calibration gas from the cylinder flows through a regulator and directly to the sample loop or preconcentrator.
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A calibration port is used to calibrate from a sampling bag, the headspace of an external container, or other external
source. The analysis port is used to sample air from the environment or from an enclosed source. When a sample
bag is utilized for analysis, the bag may be attached to the analysis port with Teflon tubing.
In the sample analysis mode, the Scentograph Plus II is used to analyze field samples. The software displays the
analysis chromatogram above the calibration chromatogram and identifies each peak as it appears. The names,
concentration levels, and retention times of the compounds that match those identified during calibration are listed.
Compounds detected that do not match those identified during calibration are listed as "unknown." Their retention
times and concentration levels, compared with the first calibration peak, are also displayed. The "unknown"
compounds may be identified by computer-assisted methods. Sample analysis results may be compared with other
calibration results stored in the Scentograph Plus II memory, or libraries that contain hundreds of compounds may
be scanned for retention time matches. Since calibration and sample analysis modes are operated under the same
conditions, and because calibration can be performed as frequently as required, the analysis results obtained with
the Scentograph Plus II are highly reliable and accurate.
Detector Systems
For this demonstration, the Scentograph Plus II was configured with a combined MAID/ECD detector module. The
following paragraphs discuss this detector system in detail.
Microargon lonization Detector
This mode is suitable for the detection of most organic compounds. Its simplicity and ruggedness make it ideal for
field use. The MAID enables the Scentograph Plus II to detect sub-parts-per-billion levels of many compounds. It
operates on the principle that organic compounds with ionization potentials equal to or less than the excitation
energy of argon (11.7 eV) can be ionized and detected. When the argon (Ar) carrier gas passes over a tritium (3H)
source, some argon atoms are energized to a metastable state and some are ionized. A steady stream of energized
atoms (excitons) is produced in the detector cell. When organic molecules (R) enter the detector, they collide with
the excitons. During this collision, energy from the excitons is released to the organic molecules. Since the
ionization potential of most organic compounds is less than 11.7 eV, they are ionized by the excitons. High voltage
applied across the detector produces a current that is amplified, measured, and used to produce the chromatogram.
The high energy of the argon excitons can ionize a large number of compounds, including halomethanes and
haloethanes, many of which cannot be identified by other detection methods. The following reactions summarize
how a MAID works:
3H
Ar > Ar* (energized to the excited state)
Ar* (exciton) + R (organic molecule) > Ar + R+ + e~ (electron)
Electron Capture Detector
This mode is highly sensitive and selective for such compounds as halogenated and nitrogenated hydrocarbons
capable of capturing electrons. The BCD operates by ionization of the carrier gas by a radioactive source. When
argon flows through the detector and over tritium, the following reaction occurs:
3H
Ar -^Ar+ + e~
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When a low voltage is applied across the detector, a constant current called the standing current is produced. When
a compound, such as a halogenated organic, which has an affinity for electrons, enters the detector, the following
reaction occurs:
RCl (halogenated compound) + e~ -» RCl~
The compound "captures" the electron and becomes a negative ion. The light, fast-moving electrons in the detector
are converted to heavy, slow-moving ions. The mobility of the negative charge is decreased, resulting in a decrease
in the number of negative charges reaching the electrode. This reduction in current is amplified and measured.
The Scentograph Plus II uses high-purity argon from an internal cylinder for the MAID/ECD configuration and
helium carrier gas for the photoionization detector (PID) or thermal conductivity detector (TCD) detection modes.
Sample Injection
Three methods can be used to introduce samples into the Scentograph Plus II: a preconcentrator, a sample loop, or
a heated injection port. In this demonstration, a preconcentrator was used.
Preconcentrator
The Scentograph II is normally equipped with a preconcentrator for use when sample concentrations are expected
to be 100 parts per million (ppm) or lower. It is packed with an absorbent material such as Tenax and can be
varied according to the user's application.
Sample Loop
A sample loop that allows the automatic injection of fixed volumes (usually 0.5 to 1.0 cc sample size) can be
installed in place or parallel to the preconcentrator. This loop permits analysis of sample concentrations between
1 ppm and 1000 ppm for most compounds and should be used if concentrations are expected to exceed 10 ppm.
Heated Injection Port
The Scentograph Plus II can be equipped with an optional heated on-column injection port for syringe injection of
gas or liquid. Direct injection of gas samples will attain sensitivities similar to using a sample loop. An accessory
for an on-column injection to capillary columns is also available. The Scentograph Plus II is equipped with an
automatic sampling pump with an intake rate of approximately 80 cc per minute to input sample into the
preconcentrator or sampling loop from the internal calibration system, the external calibration port, or the analysis
port.
History of the Technology
The Scentograph Plus II has been evaluated for the determination of VOCs in air in three separate field studies. In
1992, its performance was evaluated at a Superfund site under remediation (Berkley et al, 1993). The system was
also evaluated in June 1994 for measurement of vinyl chloride emissions at a landfill adjacent to a residential area
(Linenberg, 1995). In another study, downwind VOC vapors from an artificial pollution source were analyzed
(Berkley et al., 1996).
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Applications
The Scentograph Plus II can be used for continuous on-line monitoring of aqueous samples, including drinking
water, ground-water, surface water, leachate, and wastewater from hazardous waste sites.
Advantages
Some of the advantages of the Scentograph Plus II are that it:
Provides the highest sample integrity - No sample handling and storage are involved. The Scentograph Plus II
pump collects water samples in a 10-mL purge cell. Sample preservation and measurement prior to analysis are
eliminated. After each analysis the previous sample is purged with high-purity water to prevent carryover to the
next sample.
Yields timely and accurate results - The analysis is done in the field and analytical runs are often completed
within 15 minutes. The inherent error due to sample handling and transport is eliminated.
Produces off-site laboratory quality results - Certified standards are used to calibrate the system. The
Scentograph Plus II software can accommodate a five-point calibration. In the case where a single-point
calibration is used, calibration can be done as often as required. The response factors of the VOCs can be
updated daily.
Is cost effective - The availability of results within minutes can guide sample collection for additional off-site
laboratory analysis. The Scentograph Plus II can gather large volumes of replicate data that are too expensive to
generate using an off-site laboratory.
Limitations
The limiting factor of the Scentograph Plus II is its 179 °C maximum operating temperature. Although it offers
two-stage temperature ramping, the absence of a fan to cool the oven makes programming the temperature
cumbersome. In some instances, compounds may coelute, making quantitative analysis difficult.
The VOCs are identified by retention time. If the retention time of the sample peak(s) matches the retention time of
the standard peak(s), they are assumed to be the same. If any nontarget VOC has the same retention time, it can be
misidentified as a target VOC.
Performance Characteristics
Method Detection Limits
The method detection limit (MDL) concentrations for selected VOCs are listed in Table 2-1 and were determined in
accordance with 40 CFR Part 136, Appendix B.
Practical Quantitation Limit
With a 50-second purge time, it was determined that the practical quantitation limit (PQL; defined as 10 times the
standard deviation of instrument noise) for most compounds is 1 ppb. Increasing the purge time to 200 seconds
lowers the PQL of VOCs (e.g., benzene, trichloroethene, and tetrachloroethene) to 0.1 ppb.
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Table 2-1. Scentograph Plus II Method Detection Limits for Selected VOCs in Water
Analyte
Chloroform
Benzene
Trichloroethene
Tetrachloroethene
Chlorobenzene
Retention Time3 (seconds)
80
103
124
256
358
MDL (M.g/L)b
0.08
0.06
0.14
0.09
0.04
Column condition: 30 m MXT-VOL (Restek) x 0.53 mm i.d. x 3-jxm film thickness with argon carrier gas at 23 mL/minute flow rate.
Column temperature held isothermal at 70 °C. Purge time is 50 seconds.
b Determined using seven replicates of reagent water spiked with analytes at 1 ppb in accordance with the method outlined in 40 CFR Part
136, Appendix B.
Accuracy
The Scentograph Plus II performs at an accuracy level of ±20% or better over its working range 95% of the time.
Precision
The precision of the Scentograph Plus II, represented by the relative standard deviation (RSD)1 on replicate
measurements, is <20% or better over its working range.
Instrument Working Range
At a 50-second purge time, the Scentograph's range is from 1 ppb to 50 ppb. Adjusting the purge time will change
the dynamic range.
Comparison with Reference Laboratory Analyses
Prior to this demonstration, no comparative studies had been conducted.
Data Completeness
A total of 20 samples can be analyzed in a 10-hour day. The analytical sequence includes at least one calibration, a
blank, a sample duplicate, and a sample spike. This estimate is conservative in order to accommodate sample
dilutions and repeat analyses.
Specificity
The MAID can detect compounds with ionization potentials of 11.7 eV or lower. Chlorinated compounds can be
confirmed by switching from the MAID to the BCD mode.
1 The relative standard deviation is the sample standard deviation divided by the mean value and multiplied by 100.
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Other Field Performance Characteristics
Instrument Setup and Disassembly Time
One hour is required to initially assemble and condition the Scentograph Plus II. Disassembly time is about 10
minutes.
Instrument Calibration Frequency
If a multipoint calibration is performed initially, the response factor should be checked daily. If a single-point
calibration is used, then a calibration check should be repeated every ten samples.
Ancillary Equipment Requirements
Carrier Gas Cylinder and Regulator
The internal cylinder contains the required carrier gas. The carrier cylinder is easily refilled, and when filled, will
provide a minimum of 8 hours of operational time.
Batteries
Lead-acid, 6-V, 6-Ah, rechargeable batteries are used. The batteries must be recharged after each field-portable
operation (if applicable) or on a regular basis if the instrument is not in use. For fixed-location operations, the
system can be connected to an ac source, using the battery charger supplied with the unit.
Computer and Software
The Scentograph Plus II is equipped with a detachable notebook personal computer (PC) that includes a hard disk
drive and a 3.5-inch floppy disk drive. The software program that controls the Scentograph Plus II is contained on
the hard drive of the PC. Chromatographic data can be stored on either the removable diskette or the hard drive.
Field Maintenance Requirements
The internal carrier gas cylinder is refilled daily. The lead-acid battery is recharged daily after each field-portable
operation. The Scentograph Plus II requires the same preventive maintenance as a bench-top GC.
Sample Throughput Rate
A conservative estimate of sample throughput is 20 samples per 10-hour day, assuming that no significant
interferences are encountered during the analyses.
Ease of Operation
The software that controls the GC is user friendly. A few hours of training is sufficient for someone familiar with a
GC.
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Chapter 3
Demonstration Design and Description
Introduction
This chapter summarizes the demonstration objectives and describes related field activities. The material is
condensed from the Demonstration Plan for Wellhead Monitoring Technology Demonstration (Sandia, 1997),
which was reviewed and approved by all participants prior to the field demonstration.
Overview of Demonstration Design
The primary objective was to test and verify the performance of field-portable characterization and monitoring
technologies for the analysis of chlorinated VOCs in groundwater. Specific demonstration objectives are listed
below:
verify instrument performance characteristics that can be directly quantified; such factors include response to
blank samples, measurement accuracy and precision, data completeness, sample throughput, etc.;
verify instrument characteristics and performance in various qualitative categories such as ease of operation,
required logistical support, operator training requirements, transportability, versatility, and other considerations;
and
compare instrument results with data from standard laboratory analytical methods currently used to analyze
groundwater for chlorinated VOCs.
The experimental design included a consideration of both quantitative and qualitative performance factors for each
participating technology.
Quantitative Factors
The primary quantitative performance factors that were verified included such instrument parameters as precision
and accuracy, blank sample response, instrument performance at sample concentrations near its limit of detection,
sample throughput, and comparability with reference methods. An overview of the procedures used to determine
quantitative evaluation factors is given below.
Precision
Measurement uncertainty was assessed over the instrument's working range by the use of blind replicate samples
from a number of performance evaluation (PE) mixtures. Eight PE mixtures containing chlorinated VOCs at
concentrations ranging from 50 |o,g/L to over 1000 |o,g/L were prepared and distributed at each site. The mixtures
were prepared from certified standard mixes with accompanying documentation giving mixture content and purity.
The relative standard deviation was computed for each compound contained in each set of replicate PE samples and
was used as a measure of instrument precision.
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Accuracy
Instrument accuracy was also evaluated by using results from the PE samples. A mean recovery was computed for
each reported compound in each PE mixture. The average instrument result for each compound, based on four
blind replicate sample analyses, was compared against the known concentration in the PE mixture and reported as
the average percent recovery and the absolute percent difference.
Blank Sample Response
At least two blank groundwater samples were analyzed with each instrument system per demonstration day. These
were distributed as blind samples in the daily set of samples provided to each instrument operator. The results from
these samples were used to assess the degree to which instrument contamination and sample-to-sample carryover
resulted in a false positive.
Low-Level Sample Response
The scope of this demonstration did not include an exhaustive determination of instrument detection limits.
However, 10 replicate spiked samples at concentrations near typical regulatory action limits were provided for
analysis at each site to validate the instrument performance at these low concentration levels. The results from
these analyses were compiled as detects and nondetects and were used to calculate the percentage of correct
determinations and false negatives.
Sample Throughput
Sample throughput takes into account all aspects of sample processing, including sample preparation, instrument
calibration, sample analysis, and data reduction. The multiday demonstration design permitted the determination of
sample throughput rates over an extended period. Thus the throughput rates are representative of those likely to be
observed in routine field use of the instrument.
Laboratory-Field Comparability
The degree to which the field measurements agree with reference laboratory measurements is a useful parameter in
instrument evaluation. In this demonstration, comparisons were made on groundwater samples by computing the
absolute percent difference between laboratory and field technology results for all groundwater contaminants
detected. Linear regression of the two data sets was also carried out to determine the strength of the correlation
between the two data sets.
Qualitative Factors
Key qualitative instrument performance factors observed during the demonstration were instrument portability,
logistical support requirements, operator training requirements, and ease of operation. Logistical requirements
include the technology's power requirements, setup time, routine maintenance, and the need for other equipment or
supplies, such as a computers, reagent solutions, or gas mixtures. Qualitative factors were assessed during the
demonstration by review of vendor information and on-site audits. Vendors provided information concerning these
factors during preparation of the demonstration plan. Vendor claims regarding these specifications and
requirements are included in Chapter 2. During the field demonstration phase, auditors from the verification
organization observed instrument operation and documented the degree of compliance with the instrument
specifications and methodology. Audit results are included in Chapter 6.
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Site Selection and Description
Two sitesthe DOE Savannah River Site near Aiken, South Carolina, and McClellan Air Force Base near
Sacramento, Californiawere chosen for this demonstration. This section provides a brief history of each site, a
discussion of important geological features, and an outline of the nature and extent of contamination at each site.
The sites chosen met the following selection criteria:
presence of chlorinated VOCs in groundwater;
multiple wells at the site with a variety of contaminants and depths;
documented well-sampling history with characterization and monitoring data;
convenient access; and
support facilities and services at the site.
Savannah River Site
The Savannah River Site is operated under contract by the Westinghouse Savannah River Company. The complex
covers 310 square miles in western South Carolina, adjacent to the Savannah River, as shown in Figure 3-1. The
SRS was constructed during the early 1950s to produce the basic materials used in the fabrication of nuclear
weapons, primarily tritium and plutonium-239. Production of weapons material at the SRS also produced unusable
byproducts such as intensely radioactive waste. In addition to these high-level wastes, other wastes at the site
include low-level solid and liquid radioactive wastes, transuranic waste, hazardous chemical waste, and mixed
waste.
Figure 3-1. The general location of the Savannah River Site in
the southeast United States.
Geological Characteristics
The SRS is located on the upper Atlantic Coastal Plain. The site is underlain by a thick wedge (approximately
1000 feet) of unconsolidated Tertiary and Cretaceous sediments that overlie Precambrian and Paleozoic
metamorphic rocks and consolidated Triassic sediments (siltstone and sandstone). The younger sedimentary section
consists predominantly of sand and sandy clay. The depth to the water table from the surface ranges from 50 to
170 feet for the wells used in this demonstration.
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Groundwater and Monitoring Wells
The wells selected for sampling in this demonstration were in the A/M area, located in the northwest section of the
site. This area encompasses an abandoned process transfer line that, beginning in 1958, carried wastewater for 27
years from M-area processing facilities to a settling basin. Site characterization data indicate that several leaks
occurred in the transfer line, which is buried about 20 feet below the surface, producing localized contamination.
Past industrial operations resulted in the release of chlorinated solvents, primarily trichloroethene (TCE),
tetrachloroethene (PCE), and 1,1,1-trichloroethane, to the subsurface.
The A/M area monitoring-well network, shown in Figure 3-2, consists of approximately 400 wells. The dark
squares in the figure indicate soil borings and the light squares indicate monitoring wells. The largest group of
wells, comprising approximately 70% of the total, are associated with the plume originating from the process
transfer lines and the settling basin. The majority of these wells are constructed of 4-inch poly(vinyl chloride)
(PVC) casing with wire-wrapped screens varying in length from 5 to 30 feet. The wells are screened either in the
water-table aquifer (M-area aquifer, well depths ranging from 30 to 170 feet), the underlying tertiary aquifer (Lost
Lake aquifer, well depths ranging from 170 feet to 205 feet), or a narrow permeable zone within the confining unit
above the cretaceous aquifer (Crouch Branch Middle Sand, well depths ranging from 215 to 260 feet). The wells
are all completed with approximately 2.5 feet of standpipe above ground and a protective housing. Most wells are
equipped with a dedicated single-speed centrifugal pump (1/2 hp Grundfos Model 10S05-9) that can be operated
with a control box and generator. Wellhead pump connections also contain a flow meter and totalizer for
monitoring pumped volumes.
Light Gray = High TCE Concentrations
Dark Gray = Lower TCE Concentrations
Each Grid Square = 1000 Feet
The 10 wells used in the demonstration were located in the plume shown.
The demonstration setup area was located very near the center of the figure.
Figure 3-2. A map of the A/M area at the Savannah River Site
showing the subsurface TCE plume.
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All the wells are measured quarterly for water levels. On a semiannual basis, all point-of-compliance wells (41),
plume definition wells (236), and background wells (6) are sampled to assess compliance with groundwater
protection standards. Other water quality parameters such as conductivity, turbidity, temperature, and pH are also
measured. As a part of the monitoring program, VOCs are measured using EPA Method 8260A at an off-site
contract laboratory. The most recent (winter of 1996) quarterly water analysis results for the 10 wells used in this
demonstration are shown in Table 3-1. Well cluster numbers shown in the table include a letter designation (A
through D) that indicates the relative screening depth and aquifer zone. The A wells are the deepest of a cluster,
while the D wells mark the shallowest.
Table 3-1. Quarterly Monitoring Results for SRS Wells Sampled in the Demonstration
Sample Description
Very low 1
Very low 2
Low 1
Low 2
Mid 1
Mid 2
Very high 1
Very high 2
Very high 1
Very high 2
Well Number
MSB 33B
MSB 33C
MSB 18B
MSB 37B
MSB4D
MSB 64C
MSB4B
MSB 70C
MSB 14A
MSB8C
Compound
Trichloroethene
Tetrachloroethene
Trichloroethene
Tetrachloroethene
Trichloroethene
Tetrachloroethene
1,1-Dichloroethene
Trichloroethene
Tetrachloroethene
Carbon tetrachloride
Trichloroethene
Tetrachloroethene
Trichloroethene
Tetrachloroethene
1,1-Dichloroethene
Trichloroethene
Tetrachloroethene
Trichloroethene
Tetrachloroethene
1,1-Dichloroethane
1,1,1-Trichloroethane
Trichloroethene
Tetrachloroethene
Trichloroethene
Tetrachloroethene
Qtrly. Results3 (ng/L)
10
5
5
12
12
12
3
28
2
2
219
178
51
337
13
830
43
1290
413
61
17
3240
2440
3620
2890
a Winter 1996.
McClellan Air Force Base
McClellan Air Force Base is located 7 miles northeast of downtown Sacramento, California, as shown in
Figure 3-3. The installation consists of about 3000 acres bounded by the city of Sacramento on the west and
southwest, the city of Antelope on the north, the unincorporated areas of Rio Linda on the northwest, and North
Highlands on the east.
McClellan has been an active industrial facility since its dedication in 1936, when it was called the Sacramento Air
Depot. Operations have changed from maintenance of bombers during World War II and the Korean War, to
16
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Elverta Road
Antelope
N
' Sacramento]
99
0123
^^^^^^^^^
Scale in Miles
Figure 3-3. A map of Sacramento and vicinity showing
the location of McClellan Air Force Base.
maintenance of jet aircraft in the 1960s, and now include the maintenance and repair of communications equipment
and electronics. McClellan currently operates as an installation of the Air Force Materiel Command and employs
approximately 13,400 military and civilian personnel.
Currently, most of the industrial facilities are located in the southeastern portion of the base. The southwestern
portion has both industrial and storage areas. In the far western part are vernal pools and wetland areas. Between
these wetlands and the engine test cells, along the taxiways is an open area that was used for disposal pits.
McClellan Air Force Base is listed on the EPA Superfund National Priorities List of hazardous waste sites. The
most important environmental problem at MAFB is groundwater contamination caused by the disposal of
hazardous wastes, such as solvents and oils, into unlined pits. Approximately 990 acres beneath McClellan are
contaminated with volatile organic compounds. Remediation activities at MAFB include an extensive groundwater
pump-and-treat network, as well as soil-vapor extraction systems.
McClellan has been designated a Chlorinated Hydrocarbons Remedial Demonstration Site as part of the National
Environmental Technology Test Sites program. The Strategic Environmental Research and Development Program
is the parent organization that provides support staff for the environmental technologies undergoing development
and testing at MAFB.
17
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Geological Characteristics
Surface features at MAFB include open grassland, creeks and drainages, and vernal pools, as well as industrial,
residential, and runway areas. The land surface is a relatively flat plain that slopes gently to the west. Surface
elevations range from about 75 feet above mean sea level on the eastern side of the base to about 50 feet above
mean sea level on the western side.
Surface soils at MAFB are variable, but are generally sediments that have formed from stream erosion of granite
rocks in the Sierra Nevada. Soil in the vadose zonethe unsaturated region between the surface and the
groundwater tableis composed of interbedded layers of sands, silts, and clays. The vadose zone ranges from 90
to 105 feet. Clays and hardpan layers in this zone slow, but do not halt, infiltration of liquids into the underlying
aquifer.
The groundwater beneath MAFB behaves as one hydrogeologic unit. This single aquifer has been divided into five
groundwater monitoring zones, designated A, B, C, D, and E, from shallowest to deepest.
Groundwater and Monitoring Wells
An estimated 14 billion gallons of contaminated water underlie MAFB. Trichloroethene is the most frequently
detected contaminant in the subsurface groundwater. Over 90% of the contaminant mass is located in the A zone,
the shallowest portion of the aquifer. An estimated surface area of approximately 664 acres is underlain by a
plume in the A zone that exceeds the 5-(jg/L maximum contaminant level for TCE, as shown in Figure 3-4.
Groundwater contaminants consistently detected above federal maximum concentration limits (MCL) are shown in
Table 3-2.
Other detected compounds that are either below regulatory levels or are not currently regulated are also shown in
the table.
Monitoring wells at McClellan range from 2 to 8 inches in diameter. Well casings are Schedule 5 stainless steel
(304) and the well screen is Johnson stainless steel (304) with a 0.01- or 0.02-inch screen slot size. The screen is
surrounded by either 16 x 40 or 8 x 20 mesh gravel pack to a level about 3 feet above the screen. An
approximately 3-foot sand bridge and 3-foot bentonite seal are placed above the gravel pack. A concrete sanitary
seal containing about 3% bentonite powder is used to seal the well casing between the bentonite seal and the ground
surface.
For this demonstration, monitoring wells that penetrate both A and B aquifer zones in operational units A and B
were selected for sample collection. Quarterly monitoring data exist for 354 wells at the A and B zone aquifer
levels in these operational units. Monitoring results for TCE were used to select ten wells. Groundwater TCE
concentrations in the selected wells ranged from very low (-10 |og/L) to very high (>5000 |o,g/L) levels.
Wells that had multiple contaminants or nonchlorinated contaminants were given selection preference over those
with only a few chlorinated hydrocarbons. The most recent (winter of 1996) monitoring results for the wells chosen
for this demonstration are shown in Table 3-3.
Sample Set Descriptions
The experimental design of the demonstration specified the preparation and collection of an approximately equal
number of PE samples and groundwater samples for distribution to the participants and reference laboratory.
Descriptions of the PE and groundwater samples and their preparation are given below.
18
-------
N
0 1000
I 1 1
Scale in Feet
Figure 3-4. Subsurface TCE plumes at McClellan Air Force Base in the
shallowest (A) aquifer layer. The circular lines enclose plume concentrations in
excess of 5 ng/L TCE. OU refers to operational units. Monitoring wells used in
the demonstration were primarily in OUs A and B. The demonstration setup area
was very near OU D (upper left in the figure).
19
-------
Table 3-2. Groundwater Contaminants at MAFB
Detected above MCLa
Benzene
Carbon tetrachloride
Chloroform
1 ,2-Dichlorobenzene
1,2-Dichloroethane
1,1-Dichloroethene
1 ,2-Dichloroethene (cis and trans)
Tetrachloroethene
1,1,1-Trichloroethane
Trichloroethene
Vinyl chloride
Detected below MCL
Bromodichloromethane
Trichlorofluoromethane
Detected - Not Regulated
Acetone
2-Butanone
1,1-Dichloroethane
4-Methyl-2-pentanone
Toluene
MCL = maximum concentration limit.
Table 3-3. Quarterly Monitoring Results for MAFB Wells Sampled in the Demonstration
Sample Description
Very low 1
Very low 2
Low 1
Low 2
Midi
Mid 2
Highl
High 2
Well Number
EW-86
MW-349
MW-331
MW-352
EW-87
MW-341
MW-209
MW-330
Compound
Trichloroethene
1,1-Dichloroethene
Trichloroethene
Tetrachloroethene
Chloroform
Acetone
1,1-Dichloroethane
Carbon tetrachloride
Chloroform
Trichloroethene
c/s-1 ,2-Dichloroethene
1,1-Dichloroethane
Tetrachloroethene
Freon11
1,1,1-Trichloroethane
1,1-Dichloroethene
Trichloroethene
c/s-1 ,2-Dichloroethene
Trichloroethene
c/s-1 ,2-Dichloroethene
Chloroform
Trichloroethene
c/s-1 ,2-Dichloroethene
frans-1 ,2-Dichloroethene
Chloroform
Trichloroethene
c/s-1 ,2-Dichloroethene
frans-1 ,2-Dichloroethene
Qtrly. Results3 (ng/L)
8
13
9
5
8
9
16
5
7
19
41
6
5
115
17
334
220
5
350
18
53
586
80
13
44
437
64
9
20
-------
Table 3-3. Quarterly Monitoring Results for MAFB Wells Sampled in the Demonstration
(Continued)
Sample Description
Very high 1
Very high 2
Well Number
MW-334
MW-369
Compound
1,1-Dichloroethene
Benzene
Carbon tetrachloride
Chloroform
Dichloromethane
Trichloroethene
c/s-1 ,2-Dichloroethene
Xylene
1,2-Dichloroethane
Carbon tetrachloride
Chloroform
Tetrachloroethene
Trichloroethene
c/s-1 ,2-Dichloroethene
Qtrly. Results3 (ng/L)
1000
705
728
654
139
20,500
328
59
13
91
84
6
10,200
246
Winter 1996.
PE Samples and Preparation Methods
Three different commercially available (Supelco, Bellefonte, Pennsylvania) standard solutions of chlorinated VOCs
in methanol were used to prepare the PE mixtures. The standard solutions were supplied with quality control
documentation giving the purity and weight of the compounds in the mixture. The contents of the three mixtures,
termed mix 1, mix 2, and mix 3, are given in Table 3-4. VOC concentration levels in these standard solutions were
either 200 |o,g/L or 2000 |o,g/L. The PE mixtures were prepared by dilution of these standard solutions.
The number of replicate samples and the compound concentrations from each of the nine PE mixtures prepared at
each site are given in Table 3-5 for the SRS and Table 3-6 for MAFB. Ten replicates of the mixture with the
lowest concentration level were prepared so technology performance statistics near typical regulatory action levels
could be determined. Four replicates were prepared for each technology and the reference laboratory from the other
eight PE mixtures. The highest-level PE mixture, denoted "spike/low" in the tables, consisted of high-level (>1000
Hg/L) concentrations of TCE and PCE (and other compounds at MAFB as noted in the table) in the presence of a
low-level (50 or 100 ng/L) PE mixture background. Eight blank samples were also provided to each technology at
each site. The blank samples were prepared from the same batch of deionized, carbon-filtered water used to
prepare the PE mixtures.
Performance evaluation mixtures were prepared in either 8-L or 10-L glass carboys equipped with bottom spigots.
Stock PE solutions were dispensed with microsyringes into a known volume of deionized, carbon- filtered water in
the carboy. The mixture was gently stirred for 5 minutes with a Teflon-coated stir bar prior to dispensing samples
from the bottom of the carboy. A twofold excess volume of PE mixture was prepared in order to ensure a sample
volume well in excess of the required volume. The mixture was not stirred during sample dispensing to minimize
headspace losses in the lower half of the carboy. Headspace losses that did occur during dispensing were limited to
the top portion of the mixture, which was discarded after the samples were dispensed. Samples were dispensed into
bottles specified by participants (40 mL, 250 mL, and 1 L) with zero
21
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Table 3-4. Composition of PE Source Materials
PE Mix 1 - Purgeable A
Supelco Cat. No. 4-8059
Lot LA68271
Trichlorofluoromethane
1,1-Dichloroethane
Dichloromethane
1,1-Dichloroethene
Chloroform
Carbon tetrachloride
Trichloroethene
1 ,2-Dichloropropane
1,1,2-Trichloroethane
Tetrachloroethene
Dibromochloromethane
Chlorobenzene
1 ,2-Dichlorobenzene
2-Chloroethyl vinyl ether
PE Mix 2 - VOC 3
Supelco Cat. No. 4-8779
Lot LA64701
1,1-Dichloropropene
1,2-Dichloroethane
Trichloroethene
1 ,2-Dichloropropane
1,1,2-Trichloroethane
1 ,3-Dichloropropane
1 ,2-Dibromoethane
1,1,1 ,2-Tetrachloroethane
1 ,1 ,2,2-Tetrachloroethane
1 ,2,3-Trichloropropane
1 ,2-Dibromo-3-chloropropane
c/s-1 ,3-Dichloropropene
frans-1 ,3-Dichloropropene
Hexachlorobutadiene
PE Mix 3 - Purgeable B
Supelco Cat. No. 4-8058
Lot LA 63978
1,2-Dichloroethane
1 ,1 ,2,2-Tetrachloroethane
c/s-1 ,3-Dichloropropene
frans-1 ,3-Dichloropropene
frans-1 ,2-Dichloroethene
1,1,1-Trichloroethane
Benzene
Bromodichloromethane
Toluene
Ethyl benzene
Bromoform
Table 3-5. PE Sample Composition and Count for SRS Demonstration
Sample Concentration Level
Very low level
Low level
Mid level
High level
Spike / low
Total number of samples
PE Mixture - Mixture Concentration3
VOC Mix 1 -10|ig/L
VOC Mix 1 - 50 |ig/L
VOC Mix 2- 100|ig/L
VOC Mix 1 - 200 |ig/L
VOC Mix 2- 200|ig/L
VOC Mix 1 - 600 |ig/L
VOC Mix 2- 800|ig/L
1 .02 mg/L TCE spike + 50 |ig/L mix 1
1 .28 mg/L TCE and 1 .23 mg/L PCE
spike + 1 00 |ig/L mix 2
No. of Replicates
10
4
4
4
4
4
4
4
4
42
a TCE = trichloroethene; PCE = tetrachloroethene.
headspace. The samples for field analysis were not preserved with chemical additives since sterile, nutrient-free
water was used in their preparation.
Reference laboratory samples were preserved by acidification as specified in Method 8260A. Following
preparation, all samples were kept under refrigeration until they were distributed to participants. All PE mixtures
were prepared and dispensed on the weekend before the demonstration week.
22
-------
Table 3-6. Sample Composition and Count for MAFB Demonstration
Sample Concentration Level
Very low level
Low level
Mid level
High level
Spike / low
Total number of samples
PE Mixture - Mixture Concentration3
VOC Mix 3- 10|ig/L
VOC Mix 3 - 50 jjg/L
VOCMix2- 100|ig/L
VOC Mix 3 - 200 jjg/L
VOC Mix 2- 300|ig/L
VOC Mix 1 - 600 jjg/L
VOC Mix 2- 800|ig/L
1 .22 mg/L TCE, 1 .00 mg/L PCE, 0.50 mg/L 1 1 DCA,
and 0.50 mg/L BNZN spike + 1 00 ug/L mix 3
1 .04 mg/L 1 1 DCA, 0.86 mg/L BNZN, 0.57 mg/L
TCE, and 0.51 mg/L PCE spike + 50 ug/L mix 2
Number of
Replicates
10
4
4
4
4
4
4
4
4
42
TCE = trichloroethene; PCE = tetrachloroethene; 11 DCA = 1,1 -dichloroethane; BNZN = benzene.
Groundwater Samples and Collection Methods
A total of 33 groundwater samples were provided to each participant and reference laboratory at each
demonstration site. These samples were collected from ten wells selected to cover TCE concentrations ranging
from 10 ug/L to >1000 ug/L. The presence of other groundwater contaminants was also considered in well
selection, as noted previously. Samples from each well were prepared in either triplicate or quadruplicate to allow
statistical evaluation of instrument precision and accuracy relative to the reference laboratory results.
Groundwater at both sites was sampled by the same contract personnel who conduct sampling for quarterly well
monitoring. Site-specific standard operational procedures, published in the demonstration plan, were followed at
both sites. The sampling procedure is briefly summarized in the next paragraph.
The wells were purged with three well volumes using a submersible pump. During the purge, pH, temperature, and
conductivity were monitored. Following well purge, pump flow was reduced and the purge line was used to fill a
10-L glass carboy. This initial carboy volume of groundwater was discarded. The carboy was filled to between 9
and 10 L a second time at a fill rate of 2 to 3 L/minute with the water stream directed down the side of the carboy
for minimal agitation. The filled carboy was gently mixed with a Teflon stir bar for 5 minutes. Zero-headspace
samples were immediately dispensed from the carboy while it was at the wellhead in the same manner as PE
samples. Either three or four replicate samples were prepared for each technology and the reference laboratory.
Following dispensing, the sample bottles were placed in a cooler and held under refrigeration until they were
distributed to the participants. Groundwater sampling was completed during the first 2 days of each demonstration.
Lists of the sampled wells and quarterly monitoring results are given in Tables 3-1 and 3-3 for the SRS and MAFB,
respectively.
Sample Handling and Distribution
The distribution and status of all samples were tracked with chain-of-custody forms. Samples were dispensed to
participants in small coolers containing a supply of blue ice. Normally, two sets of either 10 or 11 samples were
distributed to participants each day during the 4 days of the demonstration, for a total of 83 samples, including
blanks, at each site.
23
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Some of the participants required information concerning the content of the samples prior to carrying out an
analysis. This information was noted on the chain-of-custody form for each PE and groundwater sample, and was
made available to the participants. Recorded information included:
number of contaminants in the sample;
list of contaminants in the sample;
boiling point range of sample constituents; and
approximate concentration range of contaminants in sample (low, mid, high).
The type of information provided during this demonstration would be required by the technology as a part of its
normal operational procedure and did not compromise the results of the test. The information provided to each of
the participants is documented in Chapter 5.
Field Demonstration Schedule and Operations
The following schedule was followed at both sites. The field team arrived on the Thursday prior to the
demonstration week. Performance evaluation samples were prepared on Friday, Saturday, and Sunday.
Technology participants arrived at the site on Monday morning and immediately began instrument setup. The first
set of PE samples was normally distributed to all participants by midday Monday. The groundwater sampling
crew, consisting of at least two on-site contractors and at least one ETV field-team member, carried out sampling of
the 10 wells on Monday and Tuesday. The first groundwater samples were distributed on Wednesday. Thursday
was reserved as a visitor day during which local and regional regulatory personnel and other potential instrument
users were invited to hear presentations about instrument capabilities as well as to view the instruments in
operation. Sample analysis was also performed on Thursday. On Friday, the final day of the demonstration,
participants finished sample analysis, packed up, and departed by midafternoon.
Site Operations and Environmental Conditions
Instruments were deployed in parking lots or open fields adjacent to the well networks sampled during each
demonstration. All participants came to the site self-equipped with power and shelter. Some came with field-
portable generators and staged under tent canopies; others operated their instruments inside vehicles and used dc-to-
ac power inverters connected to the vehicle's battery. Tables were provided for those participants who required a
work space. Each team provided its own instrument operators. Specifics regarding instrument setup and the
qualifications, training, and experience of the instrument operators are given in Chapter 6.
The SRS demonstration took place on September 8 through 12, 1997, and the MAFB demonstration on
September 22 through 26, 1997. The verification organization team staged its operations out of a tent at the SRS
and out of a mobile laboratory at MAFB. The PE mixtures at the SRS were prepared at a nearby SRS laboratory
facility and in the mobile laboratory at MAFB. Refrigerators at on-site facilities of the groundwater sampling
contractors were used to store the samples at both sites prior to their distribution.
Environmental conditions at both sites are summarized in Table 3-7. Conditions at SRS were generally hot and
humid. Sporadic rain showers were encountered on one of the test days, but did not impede demonstration
activities. Conditions at MAFB were initially hot and progressed to unseasonably hot. Moderately high winds
were also encountered during the last 2 days at MAFB.
24
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Table 3-7. Weather Summary for SRS and MAFB During Demonstration Periods
Site/Parameters
Mon
Tue
Wed
Thu
Fri
SRS
Temperature range (°C)
Relative humidity range (%)
20-34
25-68
21 -33
28-67
21 -28
51 -71
18-30
40-70
19-33
26-70
MAFB
Temperature range (°C)
Relative humidity range (%)
Wind speed range (knots)
17-33
17-72
0-7
18-36
25-47
3-6
18-37
15-59
1 -6
24-35
17-67
4-13
24-35
31 -83
2-11
Note: Ranges are given for the 7 a.m. to 7 p.m. time interval.
Field Audits
Field auditors were used to observe and record specific features of technology operations. The demonstration goal
was to have at least two auditors observe each technology over the course of the two field demonstrations. Audit
results are documented in Chapter 6. The following checklist was used by the audit team as a guideline for
gathering information during the audit:
description of equipment used;
logistical considerations, including size and weight, shipping and power requirements, other required accessories;
historical uses and applications of the technology;
estimated cost of the equipment and its field operation;
number of operators required;
required operator qualifications;
description of data produced;
compounds that the equipment can detect;
approximate detection limits for each compound, if available;
initial calibration criteria;
calibration check criteria;
corrective actions for unacceptable calibrations;
specific QC procedures followed;
QC samples used;
corrective action for QC samples;
sample throughput rate;
time requirements for data analysis and interpretation;
data output format and description;
specific problems or breakdowns occurring during the demonstration;
possible sample matrix interference; and
other auditor comments and observations.
25
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Data Collection and Analysis
The analytical results were collected in hardcopy format at the end of each day. These results were used to
document sample completion and throughput. The participants also provided a compilation of their results on
computer disks at the conclusion of each demonstration week. No feedback on analytical results or performance
was given to the participants during the course of either demonstration week. Following the SRS demonstration,
and only after all results were submitted, was qualitative verbal feedback given to each participant concerning their
accuracy and precision on SRS PE sample results. This was reasonable since a well-defined monitoring plan would
use preliminary samples to determine control limits and to make system modifications or refinements prior to
advancing to the next phase of sampling and analysis. Three weeks following the MAFB demonstration, copies of
all submitted data were entered into spreadsheets by the verification organization and transmitted to participants for
final review. This gave each participant the opportunity to detect and change calculation or transcription errors. If
other more substantive changes were proposed, they were submitted to the verification organization, along with
documentation outlining the rationale for the change. Following this final data review opportunity, no other data
changes were permitted. The extent and nature of any changes are discussed in Chapter 6.
Demonstration Plan Deviations
The following deviations from the written demonstration plan were recorded during the field demonstration. The
impact of each deviation on the overall verification effort, if any, is also included.
Five blank samples were submitted to the reference laboratory from the SRS demonstration instead of the
8 samples specified in the demonstration plan. The impact on the verification effort was minimal since a total of
13 blanks (8% of the total field sample count) were analyzed by the reference laboratory.
During groundwater sampling of SRS well MSB 14A, two 250-mL sample bottles were not filled. Omission of
this sample resulted in a double replicate sample set instead of a triple replicate for Electronic Sensor Technology
and Sentex. The impact on the study was insignificant since this omission accounted for only 1 sample out of a
total groundwater sample count of 33.
The demonstration plan specified that only two VOC mixtures would be used at each demonstration site. In fact,
three mixtures were used at the MAFB demonstration (Table 3-6) to add complexity to the sampling. This
change caused some minor confusion with one of the developers, who was not expecting this particular set of
compounds at MAFB. The most significant impact of this change was a loss of time for the affected developer as
a result of extended data review of the unanticipated mixture. The misunderstanding was verbally clarified and
no further problems were encountered. The results from the high-level VOC mix 1 were not used in the statistical
analyses.
26
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Chapter 4
Laboratory Data Results and Evaluation
Introduction
A reference laboratory was used to verify PE sample concentrations and to generate analytical results for all
groundwater samples using EPA Method 8260A. This chapter includes a brief description of the reference
laboratory and its data quality control program; the methodology and accompanying quality control procedures
employed during sample analysis; and laboratory results and associated measures of data quality for both
demonstration sites.
Reference Laboratory
DataChem Laboratories (DCL) in Salt Lake City, Utah, was chosen as the reference laboratory for both phases of
this demonstration. This is a full-service analytical laboratory with locations in Salt Lake City and Cincinnati,
Ohio. It provides analytical services in support of environmental, radiological, mixed-waste, and industrial hygiene
programs. DataChem's qualifications include U.S. EPA Contract Laboratory Program participation in both
inorganic and organic analysis and American Industrial Hygiene Association accreditation, as well as U.S. Army
Environmental Center and U.S. Army Corps of Engineers (Missouri River Division) certification. State-specific
certifications for environmental analytical services include Utah, California, Washington, New Jersey, New York,
Florida, and others.
Laboratory Selection Criteria
Selection criteria for the reference laboratory included the following: relevant laboratory analytical experience,
adequacy of QC documentation, turnaround time for results, preselection audit results, and cost. Early discussions
with DCL revealed that the laboratory conducts a high number of water analyses using Method 8260A. Prior to
laboratory selection, a copy of the DataChem Quality Assurance Program Plan (DataChem, 1997) was carefully
reviewed. This document outlines the overall quality assurance program for the laboratory and provides specific
quality control measures for all the standard analytical methods used by the laboratory. Laboratory analysis and
reporting time for sample analysis was 21 days, with a per-sample cost of $95.
In June 1997, Sandia sent several PE water samples to DCL for evaluation. Laboratory performance on these
samples was reviewed during an audit in June 1997. The laboratory detected all compounds contained in the PE
mixtures. Reported concentration levels for all compounds in the mixtures were within acceptable error margins.
The audit also indicated that the laboratory conducted its operations in accordance with its QA plan. The results of
this preliminary investigation justified the selection of DCL as the reference laboratory and provided ample
evidence of the laboratory's ability to correctly use Method 8260A for the analysis of demonstration samples.
27
-------
Summary of Analytical Work by DataChem Laboratories
In addition to the preselection audit samples noted above, DCL also analyzed predemonstration groundwater
samples collected at SRS in August 1997. During the demonstration phase, DCL was sent split samples of all PE
and groundwater samples given to the demonstration participants from both the Savannah River and McClellan
sites. A total of 90 and 91 samples from the SRS and MAFB demonstrations, respectively, were received and
analyzed by the laboratory. Over the course of one month, demonstration samples were run in nine batches of
approximately 20 samples per batch. The results were provided in both hardcopy and electronic format. The hard
copy included all paperwork associated with the analysis, including the mass spectral information for each
compound detected and complete quality control documentation. The electronic copy was provided in spreadsheet
format and included only the computed result for each target compound in each sample.
Preselection evaluation of DCL established their competence in the use of Method 8260A. In light of these findings
and in an effort to expedite laboratory analysis of demonstration samples, an estimate of the concentration levels of
target compounds in both PE and groundwater samples was provided to the laboratory with each batch of samples.
With a knowledge of the approximate concentration range of the target compounds, the analyst was able to dilute
the sample appropriately, thereby eliminating the need to do multiple dilutions in order to obtain a suitable result
within the calibrated range of the instrument.
Summary of Method 8260A
Method 8260A, which is included in the EPA SW-846 compendium of methods, is used to measure volatile organic
compounds in a variety of solid waste matrices, including groundwater (EPA, 1996b). The method can be used to
quantify most volatile organic compounds with boiling points below 200 °C that are either insoluble or only slightly
soluble in water. The method employs a chromatography/mass spectrometric procedure with purge-and-trap
sample introduction. An inert gas is bubbled through a vessel containing the water sample. The volatile organic
compounds partition into the gas phase and are carried to a sorbent trap, where they are adsorbed. Following the
purge cycle, the sorbent trap is heated and the volatile compounds are swept into the GC column, where they are
separated according to their boiling points. The gas chromatograph is interfaced directly to a mass spectrometer
that bombards the compounds with electrons as they sequentially exit the GC column. The resulting fragments,
which possess charge and mass characteristics that are unique for each compound, are detected by the
spectrometer's mass detector. The signal from the mass detector is used to build a compound mass spectrum that is
used to identify the compound. The detector signal intensities for selected ions unique to each target compound are
used to quantify the amount of the compound in the sample.
Method 8260A Quality Control Requirements
Method 8260A specifies a number of quality control activities to be carried out in conjunction with routine sample
analysis. These activities are incorporated into DCL QA documentation and are summarized in Table 4-1
(DataChem, 1997). Corrective actions are specified in the event of failure to meet QC criteria; however, for the
sake of brevity they are not given in the table. In most cases the first corrective action is a calculation check. Other
corrective actions include system recalibration, sample rerun, batch rerun, or flag data.
Summary of Laboratory QC Performance
The following sections summarize the QC activities and results that accompanied the analysis of each sample batch.
28
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Table 4-1. Method 8260A Quality Control Summary
Activity
Spectrometer tune check
System performance
check
System calibration check
Lab method blank
Field blank
Laboratory control
standard
Matrix spike
Matrix spike duplicate
Surrogate standards
Internal standards
Frequency
Bromofluorobenzene
standard every 12 hours
SPCCa sample every 12
hours
CCCb sample every 1 2
hours
One or more per batch
(approx. 20 samples)
One or more per batch
One or more per batch
One or more per batch
One or more per batch
Included in every sample
Included in every sample
Data Acceptance Criteria
Relative abundance; range of characteristic mass
fragments meets specifications.
Compound relative response factors must exceed
required minimums.
Response factor of CCC varies by no more than +25%
from initial calibration.
Internal standard retention time within 30 seconds of last
check.
Internal standard area response within -50 to 1 00% of
last check.
< 3x Detection limit.
< 3x Detection limit.
Compound recovery within established limits.0
Spike recovery within established limits. c
Relative percent difference of check compounds <50%.
Recovery within established limits. c
Recovery within established limits. c
SPCC = system performance check compounds.
b CCC = calibration check compounds.
0 The laboratory generates control limits that are based on 100 or more analyses of designated compounds. The upper and lower acceptable recovery limits
are based on a 3-standard-deviation-interval about the mean recovery from the multiple analyses. The result from a single analysis must fall within these
control limits in order to be considered valid.
Target Compound List and Method Detection Limits
The method detection limits and practical quantitation limits for the 34 target compounds used in this demonstration
are given in Table 4-2. The PQL marks the lower end of the calibrated working range of the instrument and
indicates the point at which detection and reported results carry a 99% certainty. Detects reported between the
MDL and PQL carry less certainty and are flagged accordingly in the tabulated results.
Sample Holding Conditions and Times
Method 8260A specifies a maximum 14-day holding time for refrigerated water samples. All samples prepared in
the field were kept under refrigeration before and during shipment to the laboratory. Upon receipt at the laboratory,
they were held under refrigeration until analysis. All samples were analyzed within the 14-day time period
following their preparation or collection.
System Calibration
Method 8260A stipulates that a five-point calibration be carried out using standard solutions for all target
compounds across the working range of the instrument. Each mix of compounds is run five times at each of the
five points in the instrument range. For an acceptable calibration, precision from these multiple analyses, as
29
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Table 4-2. Reference Laboratory Method Detection Limits for Target Compounds
Target Compound
Trichlorofluoromethane
1,1-Dichloroethane
Methylene chloride
1,1-Dichloroethene
Chloroform
Carbon tetrachloride
1,1-Dichloropropene
1,2-Dichloroethane
Trichloroethene
1 ,2-Dichloropropane
1,1,2-Trichloroethane
Tetrachloroethene
1 ,3-Dichloropropane
Dibromochloromethane
1 ,2-Dibromoethane
Chlorobenzene
1,1,1 ,2-Tetrachloroethane
1 ,1 ,2,2-Tetrachloroethane
1 ,2,3-Trichloropropane
1 ,2-Dibromo-3-chloropropane
Hexachlorobutadiene
c/s-1 ,3-Dichloropropene
frans-1 ,3-Dichloropropene
1 ,2-Dichlorobenzene
frans-1 ,2-Dichloroethene
1,1,1-Trichloroethane
Benzene
Bromodichloromethane
Toluene
Ethyl benzene
Bromoform
c/s-1 ,2-Dichloroethene
orfrto-Xylene
Acetone
Method Detection Limit
(vail.)
0.15
0.08
0.10
0.08
0.07
0.10
0.10
0.04
0.14
0.04
0.09
0.10
0.06
0.08
0.09
0.06
0.05
0.07
0.50
0.62
0.10
0.17
0.08
0.17
0.17
0.26
0.12
0.11
0.15
0.14
0.10
0.14
0.11
2.9
Practical Quantitation
Limit (ng/L)
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
5
Notes: Detection limits are given for an undiluted 5-mL sample volume. Detection limits are determined annually using the
method outlined in 40 CFR Part 136 Appendix B (seven replicates of deionized water spiked at 1 jxg/L concentration
level). Dilutions of the original sample raise the MDL and PQL values accordingly. Surrogate standards used in the
analyses were 1,2-dichloroethane-d4, toluene-d8, and 4-bromofluorobenzene. Internal standards were fluorobenzene,
chlorobenzene-ds, and 1,4-dichlorobenzene-d4.
30
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given by the relative standard deviation, must be 30% or less. A minimum instrument response factor1 is also
prescribed by the method for a designated subset of compounds termed system performance check compounds
(SPCC). The five-point calibration curve from the most recent instrument calibration met the specified precision
criteria. The system performance check compound response factors also met method criteria.
Daily Instrument Performance Checks
Daily mass spectrometer tune checks as well as other system performance and calibration checks noted in Table 4-1
were carried out for each of the nine sample batches and met Method 8260A on quality control criteria.
Batch-Specific Instrument QC Checks
Method Blanks
All method blank analyses met established criteria (Table 4-1), with one exception. Hexachlorobutadiene, one of
the demonstration target compounds, was detected in two of the method blanks at levels in excess of 3 times the
MDL. This compound was a component in one of the standard mixes used in preparing the PE samples because
reference laboratory data for this compound were not used in the study. Only one of the participating technologies
was calibrated to detect this particular compound. Occasional detection of this compound as a minor instrument
contaminant does not adversely affect the analytical results for other target compounds.
Laboratory Control Standard
At least one laboratory control standard was run with each of the nine batches of samples. Recovery values for
each component in the mixture are given in Figure 4-1 for SRS analyses and Figure 4-2 for MAFB analyses.
Recovery values were all within the laboratory-specific control criteria.
Matrix Spike and Matrix Spike Duplicate
The compounds in the matrix spike were the same as those in the laboratory control standard. Computed matrix
spike and matrix spike duplicate recoveries were all within the recovery ranges noted in Table 4-1. The relative
percent differences (RPDs)2 calculated for the matrix spike and matrix spike duplicate samples also met the
laboratory criteria of <50%. All RPD values from matrix spike analyses were less than 10% for the SRS samples
and less than 13% for MAFB samples.
Sample-Specific QC Checks
Internal Standard
All samples met internal standard acceptance criteria except one. All three internal standards in sample SP31 failed
to meet area response criteria and results from that sample were not included in the reference data set.
1 The response factor is the ratio of instrument response for a particular target compound to the instrument response for an
internal standard.
2 The relative percent difference between two samples is the absolute value of their difference divided by their mean and
multiplied by 100.
31
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DCL Laboratory Control Standard Recoveries
Savannah River Data Set
120
110
^
>
o
u
100
Batch 1
Batch 2 Batch 3
Analysis Batch No.
Batch 4
Batch 5
Figure 4-1. Laboratory control standard recovery values for SRS analyses.
DCL Laboratory Control Standard Recoveries
McClellan Data Set
120
Batch 1 Batch 2 Batch 3 Batch 4
Analysis Batch No.
Batch 5
Figure 4-2. Laboratory control standard recovery values for MAFB analyses.
32
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Surrogate Standard
With the following exceptions, surrogate standard recoveries met the criteria established by the laboratory, as noted
in Table 4-1. Six samples (SP12, SP16, SP26, SP29, SP33, and SP65) failed surrogate recovery criteria for 1,2-
dichloroethane-d4 and passed recovery criteria for 4-bromofluorobenzene and toluene-ds. The actions taken are
noted in Table 4-3.
Summary of Analytical and QC Deviations
A summary of QC deviations as well as other analytical errors or omissions is given in Table 4-3. The actions
taken with regard to the affected data and the reference data set are also tabulated, along with a brief rationale.
Table 4-3. Summary of Reference Laboratory Quality Control and Analytical Deviations
Deviation or QC Criteria Failure
Required dilution not made on two samples (SP20 and
SP21). Some compounds were present above
instrument linear range.
Three field blanks were not sent to DCL from SRS
demonstration.
Calculation error in original DCL report. Dilution factors
applied incorrectly in two samples (SP55 and SP57).
Sample SP31 failed internal standard recovery limits.
The following samples failed one or more surrogate
standard recovery limits: SP12, SP16, SP26, SP29,
SP33, and SP65.
Hexachlorobutadiene detected as a contaminant in
selected blanks and samples.
Chloroethyl vinyl ether was not detected in PE samples
known to contain this compound.
Three sample results (MG20, MG51 , and MG59) are
from a second withdrawal from the original zero-
headspace sample vial.
Action
Data Included: Data values for affected samples fall in
the range of the other three replicate samples.
No Action: Five field blanks and 10 method blanks were
run, yielding an adequate data set.
Data Corrected and Included: The correct dilution
factors were applied following a teleconference with the
DCL analyst.
Data Not Included.
Data Not Included: SP12; results clearly fall outside of
the range of other three replicate samples.
Data Included: All others; nearly all target compounds
fall within the range of concentration reported for the
other three replicate samples.
No Action: This compound was not a target compound
for any of the technologies. Its presence as a low-level
contaminant does not affect the results of other target
compounds.
No Action: The GC/MS was not calibrated for this
compound. None of the technologies included this
compound in their target compound lists.
Data Included: The original volume withdrawn from the
vial was 0.05 mL, resulting in an insignificant headspace
volume and no expected impact on the composition of
the second sample.
Other Data Quality Indicators
The demonstration design incorporated nine PE mixtures of various target compounds at each site that were
prepared in the field and submitted in quadruplicate to each technology as well as to the laboratory. Laboratory
accuracy and precision checks on these samples were assessed. Precision on replicate analysis of groundwater
samples was also evaluated. The results of these assessments are summarized in the following sections.
33
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PE Sample Precision
The relative standard deviation from quadruplicate laboratory analyses of each PE mixture prepared in the field
was computed for each target compound in the mixture. As noted in Chapter 3, care was taken to ensure the
preparation and distribution of homogeneous samples from each PE mixture. The RSD values represent an overall
estimate of precision that takes into account field handling, shipping, storage, and analysis of samples.
The precision data are shown in Figures 4-3 and 4-4 for SRS and Figures 4-5 and 4-6 for MAFB. (See Tables
3-5 and 3-6 for the composition and concentration level of each PE mixture.) The compiled RSDs for all PE sample
results had a median value of 7% and a 95th percentile value of 25%. In selected instances, precision in excess of
Method 8260A specifications (<30% RSD) is observed for tetrachloroethene, trichloroethene, c/s-1,3-
dichloropropene, 1,2,3-trichloropropane, and 1,1,2,2-tetrachloroethane. Precision well in excess of method
specifications is observed for l,2-dibromo-3-chloropropane, fra«s-l,3-dichloropropene, and 1,1-dichloropropene.
The implications of these results with respect to evaluation of the technology performance are discussed, when
applicable, in Chapters 5 or 7.
PE Sample Accuracy
An error propagation analysis was carried out to estimate the degree of uncertainty in the stated "true"
concentration level of the PE samples prepared in the field. The sources of uncertainty and their magnitude
encountered during PE sample preparation are listed in Table 4-4. These errors are combined using the
methodology described by Bevington (1969) to arrive at a combined uncertainty in the PE sample value of ±5%.
Thus, for a 100-u.g/L PE mix, the true value is known with 99% certainty to be within the range of 95 to 105 u.g/L.
Table 4-4. Sources of Uncertainty in PE Sample Preparation
Type of Uncertainty
Weight of component in PE mix
ampule.
Volume of methanol solvent used
to dilute neat compounds.
Volume of PE solution (from
ampule) used in final PE solution.
Volume of water diluent in final
PE solution.
Magnitude
O.Smg in 1200 mg
0.2 ml in 600 ml
+5% of microsyringe volume;
e.g., 25 uL for a 500-|j,L syringe
5ml in 10 L
Source of Estimate
Gravimetric balance uncertainty included
in PE mix certification documents
Published tolerances for volumetric flasks
(Fisher Catalog)
Published tolerances in certificates
shipped with microsyringes
Published tolerances for volumetric flasks
(Fisher Catalog)
The laboratory results for PE samples are compared with the "true" value of the mixture to provide an additional
measure of laboratory performance. A mean recovery3 was computed for each PE compound in each of the four
sample splits analyzed from each mixture. The SRS recovery values are shown in Figures 4-7 and 4-8, and MAFB
recoveries are shown in Figures 4-9 and 4-10. Acceptable mean percent recovery values, specified in Method
8260A, fall within the range of 70 to 130% with exceptions for a few compounds that pose analytical difficulties.
With the following exceptions, all PE compounds at all concentration ranges met the Method 8260A recovery
criteria. The exceptions are 1,2,3-trichloropropane, 1,1-dichloropropene, l,2-dibromo-3-chloropropane,
Recovery is the ratio of the mean concentration level from analysis of the four sample splits to the reference or "true"
concentration levels of the target compounds in each PE mix.
34
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Target Compound
1,2-Dichlorobenzene
Chlorobenzene
Dibromochloromethane
Tetrachloroethene
1,1,2-Trichloroethane
1,2-Dichloropropane
Trichloroethene
Carbon Tetrachloride
Chloroform
1,1-Dichloroethene
Methylene Chloride
1,1-Dichloroethane
Trichlorofluoromethane
DataChem PE Sample Precision
Site: Savannah River Mix 1
20 30
Relative Standard Deviation, %
Figure 4-3. Laboratory precision on SRS PE samples containing mix 1.
Trichloroethene was spiked into the spike/low samples.
Target Compound
Tetrachloroethene
trans-1,3-Dichloropropene
cis-1,3-Dichloropropene
1,2-Dibromo-3-Chloro pro pane
1,2,3-Trichloropropane
1,1,2,2-Tetrachloroethane
1,1,1,2-Tetrachloroethane
1,2-Dibromoethane
1,3-Dichloropropane
1,1,2-Trichloroethane
1,2-Dichloropropane
Trichloroethem
1,2-Dichloroethane
1,1-Dichloropropene
DataChem PE Sample Precision
Site: Savannah River Mix 2
,85
10 20 30
Relative Standard Deviation, %
40
50
Figure 4-4. Laboratory precision on SRS PE samples containing mix 2.
Tetrachloroethene was spiked into the mix 2 samples. Trichloroethene and
tetrachloroethene were spiked into the spike/low samples.
35
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Target Compound
Benzene
trans-1,3-Dichloropropene
cis-1,3-Dichloropropene
1,2-Dibromo-3-Chloropropane
1,2,3-Trichloropropane
1,1,2,2-Tetrachloroethane
1,1,1,2-Tetrachloroethane
1,2-Dibromoethane
1,3-Dichloropropane
Tetrachloroethene
1,1,2-Trichloroethane
1,2-Dichloropropane
Trichloroethene
1,2-Dichloroethane
1,1-Dichloropropene
1,1-Dichloroethane
DataChem PE Sample Precision
Site: McClellan Mix 2
20
30
Relative Standard Deviation, %
Figure 4-5. Laboratory precision on MAFB PE samples containing mix 2.
Trichloroethene, tetrachloroethene, 1,1-dichloroethane and benzene were
spiked into the spike/low samples.
Target Compound
Bromoform
Ethyl benzene
Toluene
Bromodichloromethane
Benzene
1,1,1-Trichloroethane
trans-1,2-Dichloroethene
trans-1,3-Dichloropropene
cis-1,3-Dichloropropene
1,1,2,2-Tetrachloroethane
Tetrachloroethene
Trichloroethene
1,2-Dichloroethane
1,1-Dichloroethane
DataChem PE Sample Precision
Site: McClellan Mix 3
20 30
Relative Standard Deviation, %
Figure 4-6. Laboratory precision on MAFB PE samples containing mix 3.
Trichloroethene, tetrachloroethene, 1,1-dichloroethane, and benzene were
spiked into the spike/low samples.
36
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Target Compound
1,2-Dichlorobenzene
Chlorobenzene
Dibromochloro methane
Tetrachloroethene
1,1,2-Trichloroethane
1,2-Dichloropropane
Trichloroethene
Carbon Tetrachloride
Chloroform
1,1-Dichloroethene
Methylene Chloride
1,1-Dichloroethane
Trichlorofluoro methane
DataChem PE Sample Recovery
Site: Savannah River Mix 1
50
) 90 100 110 120
Average Percent Recovery
Figure 4-7. Laboratory mean recoveries for SRS PE samples containing mix 1.
Trichloroethane was spiked into the spike/low samples.
Target Compound
trans-1,3-Dichloropropene
cis-1,3-Dichloropropene
1,2-Dibromo-3-Chloropropane
1,2,3-Trichloropropane
1,1,2,2-Tetrachloroethane
1,1,1,2-Tetrachloroethane
1,2-Dibromoethane
1,3-Dichloropropane
Tetrachloroethene
1,1,2-Trichloroethane
1,2-Dichloropropane
Trichloroethene
1,2-Dichloroethane
1,1-Dichloropropene
DataChem PE Sample Recovery
Site: Savannah River Mix 2
80 90 100 110 120
Average Percent Recovery
Figure 4-8. Laboratory mean recoveries for SRS PE samples containing mix
2. Trichloroethane and tetrachloroethene were spiked into the spike/low
samples.
37
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Target Compound
Benzene
trans-1,3-Dichloropropene
cis-1,3-Dichloropropene
1,2-Dibromo-3-Chloropropane
1,2,3-Trichloropropane
1,1,2,2-Tetrachloroethane
1,1,1,2-Tetrachloroethane
1,2-Dibromoethane
1,3-Dichloropropane
Tetrachloroethene
1,1,2-Trichloroethane
1,2-Dichloropropane
Trichloroethene
1,2-Dichloroethane
1,1-Dichloropropene
1,1-Dichloroethane
DataChem PE Sample Recovery
Site: McClellan Mix 2
50
80 90 100 110 120
Average Percent Recovery
Figure 4-9. Laboratory mean recoveries for MAFB PE samples containing
mix 2. Trichloroethene, tetrachloroethene, 1,1-dichloroethane, and benzene
were spiked into the spike/low samples.
Target Compound
Bromoform
Ethylbenzene
Toluene
Bromodichloro methane
Benzene
1,1,1-Trichloroethane
trans-1,2-Dichloroethene
trans-1,3-Dichloropropene
cis-1,3-Dichloropropene
1,1,2,2-Tetrachloroethane
Tetrachloroethene
Trichloroethene
1,2-Dichloroethane
1,1-Dichloroethane
DataChem PE Sample Recovery
Site: McClellan Mix 3
D Spike/Low
DMid
DLow
VLow
50
80 90 100 110 120
Average Percent Recovery
Figure 4-10. Laboratory mean recoveries for MAFB PE samples containing mix
3. Trichloroethene, tetrachloroethene, 1,1-dichloroethane, and benzene were
spiked into the spike/low samples.
38
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and 1,2-dichlorobenzene at selected concentration levels. The implications of these exceptions for the technology
evaluation are further discussed, if applicable, in Chapter 5. The compiled absolute percent differences (APDs)4
for all PE sample results had a median value of 7% and a 95th percentile value of 25%.
Groundwater Sample Precision
Relative standard deviations are given in Table 4-5 for compound concentrations in excess of 1 ng/L in
ground-water samples from the SRS demonstration. Trichloroethene and tetrachloroethene were the only
contaminants detected in SRS groundwater samples. A similar compilation of RSD values from the MAFB
groundwater samples is included in Table 4-6. These values are based on analytical results from either three or four
replicate samples. With three exceptions, all tabulated values are less than 20%.
Table 4-5. Summary of SRS Groundwater Analysis Precision
Sample Description
Very low 1
Very low 2
Low 1
Low 2
Mid 1
Mid 2
Highl
High 2
Very high 1
Very high 2
Relative Standard Deviation (%)
TCE
10.6
34.4
5.4
7.1
9.4
7.3
0.8
11.8
8.4
6.2
PCE
14.3
12.4
5.7
8.7
11.6
4.2
1.8
7.9
5.7
6.3
Table 4-6. Summary of MAFB Groundwater Analysis Precision
Sample
Description
Very low 1
Very low 2
Low 1
Low 2
Mid 1
Mid 2
Highl
High 2
Very high 1
Very high 2
Relative Standard Deviation (%)
11DCE
9.1
2.6
6.8
11.5
12.0
2.5
TCE
5.0
<0.1
3.7
5.2
10.5
3.6
2.4
5.3
5.4
8.0
CLFRM
1.3
2.0
4.9
20.9
5.3
5.2
6.4
CCL4
4.2
1.9
4.0
4.9
PCE
5.7
22.3
13.9
11DCA
<0.1
4.1
9.4
C12DCE
3.8
12.6
3.8
4.1
5.1
6.5
10.1
t12DCE
3.8
BNZN
4.9
Notes: 11DCE = 1,1 -dichloroethene; TCE = trichloroethene; CLFRM = chloroform; CCL4 = carbon tetrachloride; PCE = tetrachloroethene; 11DCA =
1,1 -dichloroethane; c12DCE = c/s-1,2-dichloroethene; (12DCE = frans-1,2-dichloroethene; BNZN = benzene.
Blank cells indicate that the compound was not present.
The absolute percent difference is the absolute value of the percent difference between a measured value and a true value.
39
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Summary of Reference Laboratory Data Quality
With the exceptions noted below, a review of DCL analytical data showed that all Method 8260A QC criteria were
met. Internal standard recovery limits were not met for one sample. The results for this sample were markedly
different from the other three samples in the replicate set and the sample was omitted from the data set. Six
samples failed one or more surrogate standard recovery criteria. These sample results were compared with
replicate sample results. Five of the six samples were comparable and were included in the reference data set.
The data for the remaining sample were not comparable and were omitted from the reference data set. Other
quality control deviations, which are summarized in Table 4-3, did not significantly affect the quality of the
laboratory data.
A review of DCL precision and accuracy on field-prepared PE mixtures corroborates laboratory internal QC
results. A similar precision evaluation on groundwater samples from both sites further supports these observations.
Overall, the internal and external QC data reveal appropriate application and use of Method 8260A by DataChem
Laboratories. The laboratory results for groundwater samples from both sites are considered suitable for use as a
reference data set.
40
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Chapter 5
Demonstration Results
Scentograph Plus II Calibrated and Reported Compounds
Prior to the field demonstration, the participants were given a list of all compounds that were to be used in the
performance evaluation (PE) mixtures to facilitate predemonstration instrument calibration. A total of 32
chlorinated and nonchlorinated hydrocarbon compounds were included in the PE mixtures noted in Table 3-4. The
Scentograph Plus II system was calibrated for and reported 19 of these compounds at both sites as shown in Table
5-1. One pair of compounds was reported as a coeluting pair. The 13 PE compounds for which the Scentograph
Plus II was not calibrated and did not report results are also given in Table 5-1.
Table 5-1. Scentograph Plus II Calibrated and Reported Compounds
PE Compounds Calibrated and Reported
1,1-Dichloroethene
Dichloromethane
1,1-Dichloroethane
1 ,2-Dichloropropane
Carbon tetrachloride(a)
1,2-Dichloroethane(a)
Trichloroethene
Toluene
Ethyl benzene
1,1-Dichloropropene
1,1,2-Trichloroethane
Tetrachloroethene
Chlorobenzene
1,1,1 ,2-Tetrachloroethane
c/s-1 ,3-Dichloropropene
frans-1 ,3-Dichloropropene
1 ,2-Dichloropropane
Benzene
frans-1 ,2-Dichloroethene
PE Compounds Not Calibrated and Not Reported
Chloroform
Dibromochloromethane
1 ,2-Dichlorobenzene
Hexachlorobutadiene
Bromodichloromethane
2-Chloroethyl vinyl ether
Bromoform
Trichlorofluoromethane
1 ,2-Dibromo-3-chloropropane
1 ,3-Dichloropropane
1 ,1 ,2,2-Tetrachloroethane
1 ,2,3-Trichloropropane
1 ,2-Dibromoethane
Note: Superscript denotes coeluting compound pairs (a).
Preanalysis Sample Information
The Sentex team requested that information on concentration accompany each of the samples. Approximate
concentration levels of the PE and groundwater sample components were noted on the chain-of-custody forms as
41
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low (<250 ppb), mid (250 to750 ppb), and high (>750 ppb). The Sentex team used this information to make the
appropriate sample dilution prior to GC analysis.
Sample Completion
All 165 PE and groundwater samples submitted for analysis to the Sentex team were completed and reported at
both demonstration sites. The demonstration plan specified a total of 166 PE and groundwater samples. As noted
in Chapter 3, one of the groundwater replicate samples was inadvertently omitted from the Sentex sample set by the
verification organization.
Blank Sample Results
Eight blank samples were provided for analysis at each demonstration site. False positive detects were counted
only for compounds reported at concentration levels greater than 1 u,g/L. No false positives were reported at either
site.
Performance at Method Detection Limit
Ten replicate samples of a PE mixture at a concentration level of 10 u,g/L were provided for analysis at each site.
Reported nondetects were compiled and are given as percent false negatives in Table 5-2. Vendor-provided
compound detection limits, where available, are also shown in the table for comparison.
Table 5-2. False Negative Rates from Very Low-Level PE Sample Analysis
SRS PEMixl (10ng/L)
Compound
1,1-Dichloroethene (NA)
Dichloromethane (NA)
Carbon tetrachloride (NA)
1 ,2-Dichloropropane (NA)
Trichloroethene (0.14)
1 ,1 ,2-Trichloroethane (NA)
Tetrachloroethene (0.09)
Chlorobenzene (0.04)
2-Chloroethyl vinyl ether (NA)
Dibromochloromethane (NA)
Trichlorofluoromethane (NA)
1,1-Dichloroethane (NA)
1 ,2-Dichlorobenzene (NA)
False Neg.
OoflO
OoflO
OoflO
3 of 10 (30%)
OoflO
OoflO
OoflO
OoflO
No calibration
No calibration
No calibration
No calibration
No calibration
MAFB PE Mix 3 (10
Compound
frans-1,2-Dichloroethene (NA)
Benzene (0.06)
c/s-1 ,3-Dichloropropene (NA)
frans-1 ,3-Dichloropropene (NA)
Toluene (NA)
Ethyl benzene (NA)
1 ,1 ,1-Trichloroethane (NA)
1,2-Dichloroethane (NA)
Bromoform
1 ,1 ,2,2-Tetrachloroethane
Bromodichloromethane
ng/U
False Neg.
OoflO
OoflO
OoflO
OoflO
OoflO
OoflO
OoflO
10of10
No calibration
No calibration
No calibration
Notes: Vendor-provided detection limits (in jxg/L) are shown in parentheses after each compound.
NA = not available; vendor did not report method detection limits for these compounds.
PE Sample Precision
Precision results from each of the four replicate sample sets provided to the participant from eight PE mixtures at
the SRS and seven mixtures at MAFB are shown in Figures 5-1 and 5-2 for the SRS and Figures 5-3 and 5-4 for
42
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Compound
1,1-Dichloroethene
Dichloro methane
1,1-Dichloroethane
CCI4 + 12DCA
Trichloroethene
1,2-Dichloro propane
1,1,2-Trichloroethane
Tetrachloroethene
Chlorobenzene
Sentex - Scentograph Plus II PE Precision
SRS Mix1
20 30 40
Relative Standard Deviation, %
Figure 5-1. Scentograph Plus II precision on PE mix 1 at the SRS.
Compound
1,1,1-Trichloroethane
CCI4+ 12DCA
Trichloroethene
1,2-Dichloropropane
cis-1,3-Dichloropropene
trans-1,3-Dichloropropene
1,1,2-Trichloroethane
1,1,1,2-Tetrachloroethane
Tetrachloroethene
Sentex - Scentograph Plus II PE Precision
SRS Mix 2
15 20 25 30 35
Relative Standard Deviation, %
40 45
50
50
Figure 5-2. Scentograph Plus II precision on PE mix 2 at the SRS.
43
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Compound
1,1-Dichloropropene
CCI4+ 12DCA
Trichloroethene
1,2-Dichloropropane
cis-1,3-Dichloropropene
trans-1,3-Dichloropropene
1,1,2-Trichloroethane
1,1-Dichloroethane
Benzene
Tetrachloroethene
Sentex Scentograph Plus II PE Precision
MAFB Mix 2
67
67
10 20 30
Relative Standard Deviation, %
40
Figure 5-3. Scentograph Plus II precision on PE mix 2 at MAFB.
Sentex Scentograph Plus II PE Precision
10 20 30
Relative Standard Deviation, %
40
50
trans
1,
cis-'
trans-'
Compound MAFB Mix 3
1,2-Dichloroethene
1,1-Trichloroethane
Benzene
,3-Dichloropropene
Toluene
,3-Dichloropropene
Ethylbenzene
Trichloroethene
Tetrachloroethene
1,1-Dichloroethane
,
DMid
mmmm^mmmmm
piBBBBBBBtil
'
i^S^^^^^^^^^^^RRRR^ffl
'
I
M^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^Kii
50
Figure 5-4. Scentograph Plus II precision on PE mix 3 at MAFB.
44
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MAFB.: In instances where no data were reported, no graph bars are shown. The figures show the relative
standard deviation for each compound in the PE mixtures at the four concentration levels used in the study. (The
compositions and concentrations of each of these mixtures are given in Table 3-5 for SRS and Table 3-6 for
MAFB.) Note that precision and accuracy were not determined on the "very low" concentration PE mixes.
Relative standard deviations for the coeluting compound pair are also shown in the figures. Instrument precision
performance for six target compounds that are all regulated under the Safe Drinking Water act is shown in Table 5-
3. The RSDs are given for each target compound at each of the four concentration levels used in the study. The
RSD range for each target compound is also given in the last column of the table.
Table 5-3. Target Compound Precision for PE Samples at Both Sites
Target Compound
Trichloroethene
1,2-Dichloroethane
1 ,2-Dichloropropane
1,1,2-Trichloroethane
Tetrachloroethene
frans-1 ,3-Dichloropropene
Site
SRS
MAFB
SRS
MAFB
SRS
MAFB
SRS
MAFB
SRS
MAFB
SRS
MAFB
Relative Standard Deviation (%)
Low
5
11
6
36
12
8
14
7
13
4
5
Mid
6
5
7
9
6
11
7
14
10
4
24
High
17
6
27
12
11
5
6
24
3
3
9
29
Spike/Low
2
0
28
Range
0-17
6-36
5-12
6-24
3-28
4-29
Note: Blank cells indicate that no data were reported.
A summary of overall instrument precision is given in Table 5-4 for the PE mixtures used at both sites. For this
summary, RSD values from all PE sample analyses for all compounds at each site were pooled and the median and
95 percentile values of the distribution were computed.
PE Sample Accuracy
The Scentograph Plus II accuracy for PE sample analyses was determined by comparing the average value from
each of the four-sample replicate sets with the known concentration of the PE mixture (given in Tables 3-5 and
3-6 for SRS and MAFB, respectively). These comparisons are shown as percent recoveries2 in Figures 5-5 and
5-6 for SRS and Figures 5-7 and 5-8 for MAFB.3 In instances where no data were reported, no graph bars are
shown. To assist in assessing the sign of the difference, the percent recovery data are plotted as either a positive
or negative difference from the 100% recovery line. Instrument recovery performance for the six target
Precision data for the PE mix 1 sample set at MAFB are not shown. Precision results from this mixture were comparable
to those obtained from the same mixture at SRS.
Percent recovery is the Scentograph Plus II value divided by the true value, multiplied by 100.
Percent recovery data for the single PE mix 1 sample set at MAFB are not shown in a figure. Recovery results from this
mixture were comparable to those obtained from the same mixture at the SRS.
45
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Table 5-4. Summary PE Sample Precision and Percent Difference Statistics for the SRS and
MAFB
Parameter
RSD, %
Absolute percent
difference
Percentile
50th
95th
Number in pool
50th
95th
Number in pool
SRS
PE Mix 1
7
20
28
6
25
28
PE Mix 2
7
26
23
13
24
23
MAFB
PE Mix 2
11
63
25
12
66
25
PE Mix 3
8
21
18
8
24
18
Combined Sites
Combined Mixes
8
32
94
10
38
94
compounds is shown in Table 5-5. The average percent recoveries and associated ranges are given in the table for
each compound.
A summary of overall Scentograph Plus II differences relative to PE mixture true values is given for both sites,
alongside the precision summary in Table 5-4. For this summary, percent recoveries were expressed as percent
difference (e.g., a 90% recovery is equivalent to a -10% difference; a 120% recovery is equivalent to a +20%
difference) and all data from PE mixtures were pooled. The median and 95th percentile of the absolute values of
these pooled values were computed and are reported under the absolute percent difference (APD) category in
Table 5-4.4
Comparison with Laboratory Results
For each demonstration site, a total of 33 samples collected from 10 wells were provided to the participants and to
the reference laboratory. Replicate sample sets were composed of either 3 or 4 samples from each well. Average
laboratory results from each replicate set were used as the reference values for comparison with technology results.
A side-by-side comparison of laboratory and Scentograph Plus II results for all groundwater samples is given in
Tables 5-6 for SRS and 5-7 for MAFB. Well designation (very low, low, mid, high, very high) is based on TCE
concentration levels; however, other compounds were present in the groundwater samples at the concentration levels
noted in the tables. Average laboratory results for groundwater contaminants reported at levels less than 1 u.g/L are
not included in the comparisons. The precision of the Scentograph Plus II on replicate groundwater sample sets is
also shown as percent RSD in the last column of the tables.
The average percent difference between average Scentograph Plus II and laboratory results for the compounds
detected in each set of groundwater samples is shown in Figures 5-9 and 5-10 for the SRS and MAFB, respectively.
The SRS groundwater comparison in Figure 5-9 includes only TCE and PCE. Two well samples were also
contaminated with 1,1-dichloroethene, as noted in Table 5-6. More complex water samples were selected at MFB,
as indicated by the additional compounds shown in Table 5-7 and Figure 5-10.
The median and 95th percentiles of the distribution of absolute percent differences between Scentograph Plus II and
laboratory results for all groundwater samples are given in Table 5-8.
The absolute percent difference is the absolute value of the percent difference between a field and reference (in this case
reference laboratory) measurement. As an example, the percent difference between a field measurement of 85 and a
laboratory measurement of 110 is -22.7% and the absolute percent difference is 22.7%.
46
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Compound
1,1-Dichloroethene
Dichloro methane
1,1-Dichloroethane
CCI4 + 12DCA
Trichloroethene
1,2-Dichloro propane
1,1,2-Trichloroethane
Tetrachloroethene
Chlorobenzene
Sentex - Scentograph Plus II PE Recovery
SRS Mix1
0 20 40 60 80 100 120 140 160 180 200
Average Percent Recovery
Figure 5-5. Scentograph Plus II recovery on PE mix 1 at the SRS.
Compound
1,1,1 -Trichloroethane
CCI4+ 12DCA
Trichloroethene
1,2-Dichloropropane
cis-1,3-Dichloropropene
trans-1,3-Dichloropropene
1,1,2-Trichloroethane
1,1,1,2-Tetrachloroethane
Tetrachloroethene
Sentex - Scentograph Plus II PE Recovery
SRS Mix 2
20 40 60 80 100 120 140 160 180 200
Average Percent Recovery
Figure 5-6. Scentograph Plus II recovery on PE mix 2 at the SRS.
47
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Compound
1,1-Dichloropropene
CCI4+12DCA
Trichloroethene
1,2-Dichloropropane
cis-1,3-Dichloropropene
trans-1,3-Dichloropropene
1,1,2-Trichloroethane
1,1-Dichloroethane
Benzene
Tetrachloroethene
Sentex Scentograph Plus II PE Recovery
MAFB Mix 2
0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0 180.0
Average Percent Recovery
Figure 5-7. Scentograph Plus II recovery on PE mix 2 at MAFB.
Compound
trans-1,2-Dichloroethane
1,1,1-Trichloroethane
Benzene
cis-1,3-Dichloropropene
Toluene
trans-1,3-Dichloropropene
Ethylbenzene
Trichloroethene
Tetrachloroethene
1,1-Dichloroethane
Sentex Scentograph Plus II PE Recovery
MAFB Mix 3
Low
DMid
D Spike/Low
0 20 40 60 80 100 120 140 160 180 200
Average Percent Recovery
Figure 5-8. Scentograph Plus II recovery on PE mix 3 at MAFB.
48
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Table 5-5. Scentograph Plus II Target Compound Recovery for PE Mix 2 at Both Sites
Target Compound
Trichloroethene
1 ,2-Dichloroethane
1 ,2-Dichloropropane
1 ,1 ,2-Trichloroethane
Tetrachloroethene
trans-1 ,3-Dichloropropene
Site
SRS
MAFB
SRS
MAFB
SRS
MAFB
SRS
MAFB
SRS
MAFB
SRS
MAFB
Average Recovery (%)
Low
101
76
103
138
84
98
85
103
97
124
83
Mid
97
85
113
170
105
98
96
105
112
100
87
High
117
89
140
178
122
102
116
103
96
100
120
84
Spike/Low
92
101
115
Range
76-117
103-178
84-122
85-116
96-115
83-124
Note: Blank cells indicate that no data were reported.
Table 5-6. Scentograph Plus II and Reference Laboratory Results for SRS Groundwater
Samples
Sample
Description
Very low 1
Very low 2
Low 1
Low 2
Midi
Mid 2
Highl
High 2
Very high 1
Very high 2
Well
Number
MSB 33B
MSB 33C
MSB18B
MSB 37B
MSB4D
MSB 64C
MSB4B
MSB 70C
MSB 14A
MSB8C
Compound
Trichloroethene
Tetrachloroethene
Trichloroethene
Trichloroethene
Tetrachloroethene
Trichloroethene
Tetrachloroethene
Carbon tetrachloride
Chloroform
Trichloroethene
Tetrachloroethene
Trichloroethene
Tetrachloroethene
1,1-Dichloroethene
Trichloroethene
Tetrachloroethene
Trichloroethene
Tetrachloroethene
1,1-Dichloroethene
Trichloroethene
Tetrachloroethene
Trichloroethene
Tetrachloroethene
Replicates
3
3
3
4
4
3
3
4
3
3
Lab.
Avg.
(ng/L)
9.0
3.5
2.4
11
27
27
22
1.0
1.3
150
87
35
240
12
747
33
1875
520
32
1367
800
4933
3668
Range
Median
95th Percentile
Lab.
RSD
(%)
11
14
34
5
6
7
9
15
0
9
12
7
4
8
1
2
12
8
8
8
6
6
6
0-34
8
15
Plus lla
Avg.
(ng/L)
6.0
3.0
7.3
9.7
41
32
40
NR
NR
158
95
NR
263
NR
1214
NR
2073
927
NR
1335
754
4911
7215
Plus lla
RSD
(%)
0
0
87
16
19
6
17
NR
NR
12
20
NR
10
NR
7
NR
5
15
NR
87
87
1
4
0-87
12
87
NR = not reported.
49
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Table 5-7. Scentograph Plus II and Reference Laboratory Results for MAFB Groundwater
Samples
Sample
Description
Very low 1
Very low 2
Low 1
Low 2
Midi
Mid 2
Highl
High 2
Very high 1
Very high 2
Well
Number
EW-86
MW-349
MW-331
MW-352
EW-87
MW-341
MW-209
MW-330
MW-334
MW-369
Replicates
3
3
4
3
4
3
3
4
3
3
Compound
Trichloroethene
1,1-Dichloroethene
Trichloroethene
Tetrachloroethene
Chloroform
1,1-Dichloroethene
Carbon tetrachloride
1,1-Dichloroethene
1,1-Dichloroethane
c/s-1 ,2-Dichloroethene
Carbon tetrachloride
Chloroform
Trichloroethene
Freon11
1,1-Dichloroethene
1,1-Dichloroethane
c/s-1 ,2-Dichloroethene
Carbon tetrachloride
Trichloroethene
1,1-Dichloroethene
1,1-Dichloroethane
c/s-1 ,2-Dichloroethene
1,1,1 -Trich loroethane
Trichloroethene
Tetrachloroethene
c/s-1 ,2-Dichloroethene
Chloroform
Trichloroethene
c/s-1 ,2-Dichloroethene
Chloroform
Trichloroethene
frans-1 ,2-Dichloroethene
c/s-1 ,2-Dichloroethene
Chloroform
1 ,2-Dibromochloropropane
Trichloroethene
1,1-Dichloroethene
c/s-1 ,2-dichloroethene
Chloroform
Benzene
Trichloroethene
Carbon tetrachloride
c/s-1 ,2-Dichloroethene
Chloroform
Carbon tetrachloride
Trichloroethene
Lab.
Avg.
(ng/L)
4.6
7.7
13
2.0
9.0
3.8
137
2.5
15
NR
7.5
4.8
16
20
1.5
5.1
1.5
1.4
22
180
3.0
3.3
6.8
114
1.2
15
3.5
280
38
6.9
238
7.7
66
42
6.1
380
690
237
397
283
10,667
350
207
63
51
6167
Range
Median
95th Percentile
Lab.
RSD
(%)
5
9
0
6
1
3
4
7
0
NR
2
2
4
6
12
4
4
4
5
12
9
13
12
11
14
4
5
4
4
21
2
4
5
5
6
5
3
7
5
5
5
5
10
6
5
8
0-21
5
13
Plus lla
Avg.
(WJ/L)
4.3
7.7
33
NR
26
NR
NR
NR
14
31
6.0
NR
17
NR
NR
NR
NR
NR
21
159
NR
NR
NR
99
NR
NR
NR
248
195
NR
199
NR
52
NR
NR
325
NR
NR
NR
NR
11,031
NR
NR
NR
NR
5486
Plus lla
RSD
(%)
13
8
8
NR
10
NR
NR
NR
0
2
0
NR
0
NR
NR
NR
NR
NR
10
6
NR
NR
NR
9
NR
NR
NR
4
4
NR
0
NR
67
NR
NR
7
NR
NR
NR
NR
1
NR
NR
NR
NR
1
0-67
6
24
NR = not reported.
50
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Compound
Sentex Scentograph Plus II GW Sample Difference
Site: Savannah River Ref: Laboratory
Tetrachloroethene
Trichloroethene
VHigh2
DVHigM
High2
DHighl
Mid2
Low2
GLOW!
DVLow2
QVLowl
-200 -150 -100 -50 0 50 100 150 200
Average Percent Difference
Figure 5-9. Scentograph Plus II groundwater results at the SRS relative to
laboratory results.
Compound
Trichloroethene
1,1-Dichloroethane
cis-1,2-Dichloroethene
Carbon tetrachloride
1,1-Dichloroethene
Dichloromethane
Chloroform
Sentex Scentograph Plus II GW Sample Difference
MAFB Ref: Laboratory
VLowl
VLow2
Low1
Low2
Mid2
DHighl
DHigh2
VHighl
DVHigh2
154
417
184
-100 -80 -60 -40 -20 0 20 40
Average Percent Difference
80 100
Figure 5-10. Scentograph Plus II groundwater results at MAFB relative to
laboratory results.
51
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Table 5-8. Scentograph Plus II Absolute Percent Difference
Summary for Pooled Groundwater Results
Percentile
50th
95th
Number of samples in pool
SRS
14
118
17
MAFB
12
234
17
Combined Sites
12
194
34
To assess the degree of linear correlation between the Scentograph Plus II and laboratory groundwater data pairs
shown in Tables 5-6 and 5-7, correlation coefficients (r) were computed. The data pairs were divided into two
subsets for each site to reduce the likelihood of spuriously high r values caused by large differences in the data
(e.g., concentrations ranging from 1 u,g/L to those in excess of 1000 u,g/L) (Havlicek and Grain, 1988). One subset
contained all data pairs with laboratory results less than or equal to 100 u,g/L and the other subset included all data
pairs with laboratory values greater than 100 u,g/L. The computed correlation coefficients are shown in Table 5-9.
Table 5-9. Correlation Coefficients for Laboratory and Scentograph
Plus II Groundwater Analyses
Data Set
SRS Laboratory (1 through 100 |ag/L)
SRS Laboratory (> 1 00 |ag/L)
MAFB Laboratory (1 through 1 00 |ag/L)
MAFB Laboratory (> 1 00 |ag/L)
Correlation
Coefficient
0.974
0.907
0.959
0.997
Number of
Data Pairs
8
10
10
7
Sample Throughput
The Scentograph Plus II throughput was about 2 samples per hour or 16 samples per 8-hour day. Throughput
rates were assessed by using the time lapsed between sample checkout in the morning and delivery of hardcopy
results in the afternoon or the following day, and the number of samples completed. This throughput estimate
includes periodic instrument calibration checks, sample reruns, and data processing tasks. Samples with only one
or two known contaminants could be processed faster.
Performance Summary
Table 5-10 contains a summary of Scentograph Plus II performance characteristics, including important instrument
performance parameters and operational features verified in this demonstration. For groundwater samples, the
results from the reference laboratory are given alongside Scentograph Plus II performance results to facilitate
comparison of the two methodologies.
52
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Table 5-10. Scentograph Plus II Performance Summary
Instrument
Feature/Parameter
Blank sample
Detection limit sample
PE sample precision
PE sample accuracy
Scentograph Plus II
comparison with
laboratory results for
groundwater samples
Analytical versatility
Sample throughput
Support requirements
Operator requirements
Total system weight
Portability
Total system cost
Shipping requirements
Performance Summary
No false positives were reported for 1 9 calibrated compounds.
False negatives reported for two compounds at a rate of 30% (1,2-dichloropropane) and
100% (1 ,2-dichloroethane) out of 18 compounds at 10 |j,g/L concentration levels. There
were no other false negatives.
Target compounds, Scentograph Plus II RSD range: 4 to 103%
All compounds, median RSD: 8%; 95th percentile RSD: 32%
All compounds, laboratory median RSD: 7%; 95th percentile RSD: 25%
(Target compounds: TCE, PCE, 1 ,2-dichloroethane, 1,2-dichloropropane,
1 ,1 ,2-trichloroethane, frans-1 ,3-dichloropropene)
Target compounds: absolute percent difference range: 3 to 78%
All compounds, Scentograph Plus II median APD: 10%; 95th percentile APD: 38%
All compounds, laboratory median APD: 7%; 95th percentile APD: 24%
(Target compounds same as those for sample precision)
Scentograph Plus II median RSD: 8% Laboratory median RSD: 6%
Scentograph Plus II 95th percentile RSD: 87% Laboratory 95th percentile RSD: 14%
Scentograph Plus II laboratory median APD: 12% 95th percentile APD: 194%
Scentograph Plus II: laboratory correlation:
SRS low cone. (<1 00 |ag/L)r= 0.974
SRS high cone. (>1 00 |ag/L)r= 0.907
MAFB low cone. (<1 00 |ag/L)r= 0.959
MAFB high cone. (>1 00 |ag/L)r= 0.997
PE samples: calibrated for 1 9 of 32 PE compounds (59%)
One pair of coeluting compounds was reported (carbon tetrachloride and
1,2-dichloropropane).
GW samples: The reference laboratory detected 68 compounds at concentration levels of 1
|j,g/L or greater in all groundwater samples. The Scentograph Plus II was calibrated to report
62 of these compounds. The Scentograph Plus II reported values for 35 of the 62
compounds.
2 samples per hour
Tritium in the detector requires state permit or license
Sample processing: field technician
Data processing and review: experienced GC chemist
80 pounds
System is transportable
$35,000 (single column, single MAID/ECD detector)
Air freight, luggage check (no compressed gas via commercial flight)
Recharge carrier gas cylinder requires drop shipment
53
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Chapter 6
Field Observations and Cost Summary
Introduction
The following subsections summarize the audit findings obtained while observing instrument operation at both field
sites. The purpose of the audits was to observe the instrument in operation as well as to verify that analytical
procedures used during the demonstration were consistent with written procedures submitted to the verification
organization prior to the field demonstration. An instrument cost summary and an applications assessment is also
provided.
Method Summary
The Scentograph Plus II GC (Figure 6-1) incorporates a purge-and-trap GC method for the analysis of VOCs in
water. A room-temperature water sample is sparged with a volume of argon carrier gas and the entrained VOCs
are transferred to an adsorbent trap. The vapors are subsequently thermally desorbed and injected onto the column
of the Scentograph Plus II. For this demonstration, the instrument was configured with a single GC column,
programmable temperature control, and a microargon ionization/electron capture detector with tritium as the
ionization source. The detector was operated in the electron capture mode. Compounds eluting from the column
capture free electrons in the detector and thereby reduce the detector's standing current. This current reduction is
amplified and is used to generate the chromatogram. Compounds are identified by column retention time, and
quantitation is achieved by using detector response intensity.
Figure 6-1. The Scentograph Plus II GC.
54
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Equipment
The Scentograph Plus II system consists of three separate units: the Aquascana field-portable sample purge
system (7 inches x 15 inches x 20 inches, 25 pounds); the Scentograph Plus IIfield-portable gas chromatograph
(6 inches x 21 inches x 20 inches, 48 pounds); and a laptop computer (2 inches x 12 inches x 10 inches, 7 pounds),
as shown in Figure 6-1. At the demonstrations, the unit was used on the folded-down middle seat of a minivan.
The three units are field-portable, but they are best suited for use in a vehicle and not outdoors at a wellhead. The
sample purge and GC units are contained in steel cases suitable for shipping; however, they are too large to be hand
carried during air travel.
Equipment weight includes an argon carrier gas cylinder inside the instrument. A small cylinder of compressed
high-purity argon gas is used for periodic recharge of the internal cylinder. The system was powered by 110 V ac
for this demonstration. It can also be powered by a dc-to-ac inverter connected to the vehicle's battery. Additional
equipment used at the demonstration included 250-mL, screw-cap septa sample vials, standards mixtures, microliter
syringes and needles, and tubing for sample transfer.
Sample Preparation and Handling
Samples were handled in the same manner at both sites: Chilled (~ 4 °C) water samples were supplied in 250-mL
amber bottles with zero headspace. The sample was analyzed either diluted or undiluted, based upon the
anticipated concentration level of the target compounds. Dilutions of either 1:5, 1:20, or 1:50 were obtained by
pouring off a portion of a 250-mL commercial bottled water sample and making up the volume (via syringe
transfer) with cold sample from the original 250-mL sample container. (Sentex field experience indicates that
commercially available bottled water is very low in VOC content and is suitable as a low-cost, readily available
diluent.) Following dilution, if required, an extraction tube was immersed in the sample bottle and a water sample
withdrawn at a rate of 150 mL per minute for 60 seconds and flushed through a 10-mL sparge cell using a
motorized impeller pump in the purge unit. An argon gas stream was bubbled through the 10-mL sample volume
and the entrained vapors routed through tubing to a sorbent trap in the GC module. Following the adsorption cycle,
the sorbent trap was heated and carrier gas flow through the trap was used to move the vapors onto the head of the
column for separation and quantitation. All purge-and-trap and GC analysis functions were computer controlled
and were initiated by the instrument operator with keyboard commands.
Consumables
An internal gas bottle contains argon carrier gas. The internal gas supply lasts for about 8 hours and then requires
refilling. An external cylinder is used to periodically refill the internal cylinder. For long- term use, the system can
be operated from an external carrier gas cylinder.
Historical Use
The Scentograph Plus II GC has been used for monitoring industrial wastewater, sewage treatment plant effluent,
and groundwater. The GC module can also be used to monitor soil gas or air as well. The GC unit can be
equipped with a gas sampling loop instead of a sorbent trap for gas analysis applications.
Equipment Cost
The Scentograph Plus II, as equipped for this demonstration, has a purchase price of about $35,000. This includes
proprietary software, a laptop computer, and connection cables for data processing and instrument control.
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Instrument costs are summarized in Table 6-1. Reference laboratory costs were $95 per sample plus Express Mail
shipping, which was about $30 for a batch of 12 samples. The Scentograph Plus II throughput is 2 samples per
hour.
Table 6-1. Scentograph Plus II Cost Summary
Instrument/Accessory
Instrument
(Scentograph Plus II GC, field-portable Aquascan
sample unit, laptop computer, software)
Instrument accessories
(field-portable printer)
Sample handling accessories
(carrier gas, syringes, vials, standards)
Maintenance costs
Cost
$35,000
$500
$25 per day
Not determined
Operators and Training
The Scentograph Plus II analysis team consisted of three persons: a chemical technician, who operated the
instrument; a Ph. D. chemist, who assisted in instrument calibration and setup at each site; and an electronics
technician, who carried out sample handling and dilution. Only one person is required to operate the instrument.
With a half day of training, an experienced chemical technician could learn how to operate the system. A novice
technician operator would require additional training. Experience and additional training in GC data processing are
required to do method development and analysis of complex mixtures.
Data Processing and Output
The instrument uses proprietary software to control all run events (e.g., purge time, valve switching, temperature
ramps, and acquisition time). The chromatograms are stored as text files for further analysis using spreadsheet
software. A real-time, color-monitor display is available. It includes current analysis results, including compound
identification, concentration, retention time, and a chromatogram superimposed on the latest calibration
chromatogram.
Hardcopy data were not available immediately after a sample run. The system is operated under a Microsoft disk
operating system that is not capable of multitasking. To retrieve hardcopy data, the analytical software must be
shut down and the data output software started. Only analysis screen output or hardcopy output, but not both, were
available at any given time. No hardcopy data were presented or available during the audit. Final data were
provided to the verification organization in spreadsheet format on disk.
Compounds Detected
The system was calibrated for a total of 19 compounds at both sites. The calibrated compounds are listed in
Table 5-1. The system is capable of detecting organic compounds with ionization potentials of 11.7 eV or less.
The analytical method used at this demonstration resulted in one coeluting compound pair (carbon tetrachloride and
1,2-dichloroethane). The possibility of coeluting pairs requires that some information about sample content be
available so that the methods can be adjusted to minimize or avoid compound coelution.
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The microargon ionization/electron capture detector is susceptible to overloading, and thus care must be taken to
appropriately dilute the samples to the proper range prior to analysis. Detector overload requires about an hour for
complete column and detector re-equilibration, during which time samples cannot be run.
Initial and Daily Calibration
A three-point calibration was conducted daily prior to analysis of field samples. The software automatically
chooses the best curve fit routine for calibration points and stores the information in a calibration subroutine.
Choices for curve fitting are linear, second-degree, and third-degree equations. The latest calibrations are used by
the analysis routine to identify and quantify unknown analytes during the chromatographic run. During the
demonstration, the calibration was checked at the end of the day with a control standard solution. If the results
from the control standard deviated significantly (>20%) from the three-point calibration curve, a recalibration at
two points was initiated.
QC Procedures and Corrective Actions
Internal standards were not used. Blank sample analyses or corrective actions for false positives in blank samples
were not specified in the field analysis procedure. An acceptable accuracy window of ±20% was used as an
acceptance criterion for daily calibration check samples. Failure of a calibration check sample required a rerun of
the calibration standards.
Sample Throughput
Gas chromatograph analysis time was about 30 minutes per sample. Additional time was required to review and
process data. In many cases analytical results were available in real time; however, as noted earlier, hardcopy
printout could not be obtained without exiting the analysis software. Preliminary handwritten hardcopy data were
generally available the day following analysis. Sample throughput is on the order of two samples per hour. This
includes periodic instrument calibration checks, sample reruns, and all data processing tasks. Samples with only
one or two known contaminants could be processed faster.
Problems Observed During Audit
Some hardware problems were observed during the MAFB demonstration period. Toward the end of the week,
problems were encountered with the computer-GC interface. The problem was eventually determined to be a faulty
computer, and the computer was replaced. Problems were also encountered with the interface between the GC and
the Aquascan (the unit containing the purge cell, pump, and valves). A spare Aquascan unit was deployed and the
field sample analysis was completed. A complete calibration rerun was required following equipment changeout.
Data Availability and Changes
Preliminary results from each daily set of samples from the Scentograph Plus II were obtained on the following day
in handwritten format. Data were provided on disk in spreadsheet format at the conclusion of each demonstration
week. A final change to TCE and PCE values for seven samples was made following a data review by the vendor:
The field analyst noted that incorrect information on groundwater sample dilution was entered by the Sentex team
during the field analysis.
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Applications Assessment
This demonstration was designed to assess the instrument's suitability for analytical tasks in site characterization
and routine site monitoring. Site characterization refers to those instances where subsurface contamination is
suspected but information on specific compounds and their concentration level is not available. The instrument best
suited for this application is one that can screen a wide array of compounds in a timely and cost-effective manner.
Analytical precision and accuracy requirements may be relaxed in these instances since a general description of the
site characteristics is usually adequate for remediation planning. At the other end of the spectrum is a monitoring
application where contaminant compounds and their subsurface concentrations are known with some certainty.
Periodic monitoring requirements imposed by local regulatory agencies may specify that analyses be carried out for
specific contaminant compounds known to be present in the water. Quarterly well monitoring programs fall into
this category.
Based on its performance in this demonstration, the Scentograph Plus II is most applicable to routine monitoring
situations where the sample composition is known and not particularly complex. The system could also be
successfully used in sample screening situations where target contaminants are known. The instrument is able to
detect most chlorinated VOCs at submicrogram-per-liter concentration levels; thus it is well suited for monitoring
groundwater compounds at or near regulatory action levels. As with most GC systems, care must also be taken to
avoid compound coelution, and manual data processing methods may be required when coeluting compounds are
encountered in the analysis.
The observed precision and accuracy of the Scentograph Plus II is expected to be adequate for use of this
instrument in routine monitoring or screening situations. When selecting a technology for use at a site, the analyst
or site manager must take instrument performance into account, along with the project's data quality objectives.
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Chapter 7
Technology Update
Note: The following comments were submitted by the technology developer. They have been edited for format
consistency with the rest of the report. The technical content in the following comments has not been verified by
the verification organization.
Comments on Demonstration Design
The field demonstration was a good learning experience for the participants. There was frustration over the
extreme weather conditions, coupled with a few surprises and even instrument breakdown.
Suggestions for future demonstrations:
1. A specific list of target analytes should be made available. Existing laboratory methodologies give a list of target
analytes.
2. A method detection limit must be established for similar technologies. If the MDL cannot be established, at least
a prescribed practical quantitation limit must be determined.
3. An initial accuracy study must be conducted at a specific concentration level instead of determining accuracy at
different concentration levels.
4. Accuracy limits must be established by analyzing spiked samples at a given concentration and frequency.
5. An initial precision study must be conducted at a specific concentration instead of determining precision at
different concentration levels.
6. Precision limits must be established by determining the relative percent standard deviations of the percent
recovery of the spiked samples.
If a field protocol is established that is similar to the off-site laboratory protocol, fewer PE samples will be required
and more groundwater samples can be analyzed. This will more accurately reflect the throughput capability of the
GC.
The results of groundwater analysis from both sites should be combined and presented in a graph that plots the
reference laboratory data against the field data.
Additional Comments on Gas Chromatograph Performance
The drawbacks of using a field-portable gas chromatograph are the need to resolve early coeluting peaks and
extended analysis time when late-eluting peaks are present. This is primarily the case for isothermal runs.
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Although temperature ramping is available, the absence of a cooling fan makes temperature-ramped runs
impractical. The alternative to temperature ramping is the use of multiple columns. A Sentex field-portable GC
system has been developed that uses two dissimilar columns sharing the same detector and operated at a constant
temperature. A sample is taken and separation occurs in the primary column. The primary column is usually a
short, packed column that will separate early-eluting compounds (e.g., the gases, dichloroethenes, and
dichloroethanes). After elution of the early-eluting compounds, the run is stopped and the system is backflushed to
eliminate late-eluting compounds that have been introduced in the column together with early-eluting compounds.
Another sample is taken at the end of the backflush and a second column is used to separate the late-eluting
compounds (e.g., xylenes and dichlorobenzenes). The second column is usually a 30-m capillary column.
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Chapter 8
Previous Deployments
ACME Project (1993) New Jersey
The ACME project was conducted under the auspices of the New Jersey Department of Environmental Cleanup.
The investigation included approximately 800 soil borings, along with collection and on-site analyses and
quantitation of approximately 800 soil samples with the Scentograph Plus II. The objective of the on-site analytical
component of the investigation was to characterize petroleum contamination in soil for use in developing a
comprehensive cleanup plan. The analytes of interest were the purgeable aromatic hydrocarbons (benzene, toluene,
ethyl benzene, and xylenes).
DOE Remediation Site (1995). Pinellas Plant. Florida
The Aquascan was evaluated as an in-field, automated monitoring system for contaminated groundwater at an
active DOE remediation site in Pinnelas, Florida. The instrument measured concentrations of methylene chloride,
trichloroethene, and toluene in the parts per million level in the groundwater. Reported values for the three
compounds were within 20% of reference laboratory values.
Superfund Site (1996). North Carolina
A Sentex field-portable gas chromatograph was used to define a shallow and top-of-rock groundwater
contamination plume at a site in North Carolina. The analytes of interest were tetrachloroethene, trichloroethene,
and c/5-l,2-dichloroethene.
Toluene Monitoring (1996 - Present). New Jersey
A rack-type Aquascan has been installed at an industrial facility to monitor toluene levels in discharge water. It
operates in a continuous mode and sets off an alarm when the toluene level exceeds the set threshold level.
Trihalomethane Monitoring in Drinking Water (1997 - Present). Italy
A rack-type Aquascan was installed to monitor trihalomethanes in the drinking water supply.
Literature citations reporting the use of Scentograph and Aquascan instruments
Kerry M. Hanlon and Stuart S. Manley, 1993. "Quality Assurance/Quality Control Considerations for On-Site
Quantitative Analysis," in Technical Proceedings: 1993 Environmental Exposition and Conference. Connecticut
Ground-Water Association, Plantsville, CT.
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Frank Allen, 1997. "Applications of Portable GC/Purge-and-Trap in Field Analysis," in proceedings of a specialty
conference on field analytical methods for hazardous wastes and toxic chemicals, pp. 743-741. Air and Waste
Management Association. Pittsburgh, PA.
Diana S. Blair and Dennis J. Morrison, 1997. "Implementation of a Fully Automated Process Purge-and-Trap
Gas Chromatograph at an Environmental Remediation Site," in proceedings of a specialty conference on field
analytical methods for hazardous wastes and toxic chemicals, pp. 263-279. Air and Waste Management
Association, Pittsburgh, PA.
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Symposium, VIP 33, Air and Waste Management Association, Pittsburgh, PA.
Berkley, R. E., M. Davis, M. Hansen, and D. Lane, 1996, "Performance Comparison of Field Deployable Gas
Chromatographs with Canister TO-14 Analytes," in Proceedings of the 1996 U.S. EPA/Air and Waste
Management Association International Symposium, VIP-64, Air and Waste Management Association, Pittsburgh,
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DataChem, 1997, "DataChem Laboratories Environmental Chemistry/Radiochemistry Quality Assurance Program
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EPA, 1986, "Test Methods for Evaluating Solid Waste," 3rd ed., Vol. 1A. (Test Method 3810) Office of Solid
Waste and Emergency Response, Washington, DC.
EPA, 1996a, "A Guidance Manual for the Preparation of Site Characterization and Monitoring Technology
Demonstration Plans," Office of Research and Development, National Exposure Research Laboratory, Las Vegas,
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EPA, 1996b, "Test Methods for Evaluating Solid Waste: Physical/Chemical Methods; Third Edition; Final Update
III," Report No. EPA SW-846.3-3, Government Printing Office Order No. 955-001-00000-1, Office of Solid
Waste and Emergency Response, Washington, DC.
Havlicek, L. L., and R. D. Grain, 1988, Practical Statistics for the Physical Sciences, pp. 80-93. American
Chemical Society, Washington, DC.
Linenberg, A., 1995, "On-Site Monitoring of Vinyl Chloride at Parts per Trillion Levels in Air," m Proceedings of
the 1995 U.S. EPA/Air and Waste Management Association International Symposium, VIP 47, Air and Waste
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Sandia, 1997, "Demonstration Plan for Wellhead Monitoring Technology Demonstration; Sandia National
Laboratories," Albuquerque, NM. [Available at the ETV Web Site (www.epa.gov/etv) in pdf format.]
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