May 2006 

Environmental Technology 

Verification Report 

CONSTELLATION TECHNOLOGY 

CORPORATION 

CT-1128 PORTABLE GAS 

CHROMATOGRAPH-MASS SPECTROMETER 

Prepared by 

Battelle

Under a cooperative agreement with

 U.S. Environmental Protection Agency 
THE ENVIRONMENTAL TECHNOLOGY VERIFICATION

PROGRAM 

U.S. Environmental Protection Agency 

ETV Joint Verification Statement 

TECHNOLOGY TYPE: Mobile Mass Spectrometers 

APPLICATION: Monitoring volatile organic compounds, pesticides, and 

chemical agents in water 

TECHNOLOGY 

NAME: CT-1128 Portable Gas Chromatograph–Mass 

Spectrometer (GC-MS) 

COMPANY: Constellation Technology Corporation 

ADDRESS: 7887 Bryan Dairy Road PHONE: (727) 547-0600 

Suite 100 FAX: (727) 545-6150 

Largo, FL 33777-1498 

WEB SITE: www.contech.com

E-MAIL: info@contech.com

The U.S. Environmental Protection Agency (EPA) has established the Environmental Technology Verification 

(ETV) Program to facilitate the deployment of innovative or improved environmental technologies through 

performance verification and dissemination of information. The goal of the ETV Program is to further 

environmental protection by accelerating the acceptance and use of improved and cost-effective technologies. 

ETV seeks to achieve this goal by providing high-quality, peer-reviewed data on technology performance to 

those involved in the design, distribution, financing, permitting, purchase, and use of environmental 

technologies. Information and ETV documents are available at www.epa.gov/etv. 

ETV works in partnership with recognized standards and testing organizations, with stakeholder groups 

(consisting of buyers, vendor organizations, and permitters), and with individual technology developers. The 

program evaluates the performance of innovative technologies by developing test plans that are responsive to 

the needs of stakeholders, conducting field or laboratory tests (as appropriate), collecting and analyzing data, 

and preparing peer-reviewed reports. All evaluations are conducted in accordance with rigorous quality 

assurance (QA) protocols to ensure that data of known and adequate quality are generated and that the results 

are defensible. 

The Advanced Monitoring Systems (AMS) Center, one of six technology areas under ETV, is operated by 

Battelle in cooperation with EPA’s National Exposure Research Laboratory. The AMS Center evaluated the 

performance of the Constellation Technology Corporation’s CT-1128 Portable Gas Chromatograph–Mass 

Spectrometer (GC-MS). This verification statement provides a summary of the test results. 
VERIFICATION TEST DESCRIPTION 

Many volatile and semivolatile contaminants in water are detected using bench-top mass spectrometers in a 

traditional laboratory setting. However, the CT-1128 verified in this test was a portable unit designed to be 

taken outside the laboratory setting for field analysis. This portability offers an advantage to first-responders 

and other users who need chemical information when time, sampling, and other limitations preclude analysis 

in a laboratory. 

The ability of the CT-1128 to identify and quantify target contaminants was tested in various water matrices. 

The CT-1128 was evaluated for the following performance parameters: 

• Accuracy 

• Precision 

• Linearity 

• Instrument stability 

• Potential matrix and interference effects 

• Sensitivity 

• Field portability 

• Operational factors. 

Three classes of contaminants were used for testing: volatile organic compounds (benzene, toluene, ethyl 

benzene, total xylenes [BTEX]), pesticides (2,4-D and dicrotophos), and chemical warfare agents (VX, GB, 

and GD). The contaminants were selected based on recommendations from the AMS Center stakeholders. 

Performance test (PT) samples were prepared in American Society for Testing and Materials (ASTM) Type II 

water. The target contaminant concentrations were constructed to bracket the concentrations of interest, which 

were calculated using LD50 values assuming a 70-kilogram individual consuming 250 milliliters of the 

contaminated water. When LD50 data were not available or feasible for testing, maximum contaminant levels 

(MCLs), as defined by EPA National Primary Drinking Water Regulations, were used. Reference 

measurements were conducted on PT samples only, to confirm the accuracy of sample preparation. EPA 

methods 524.2 and 515.1 were used for analyzing BTEX and 2,4-D, respectively. Internally developed 

methods were used for the remainder of the contaminant reference methods since no external methods were 

available from commercial laboratories at the time of testing. 

The PT samples were used to determine the accuracy of the CT-1128; one set of which was used to establish a 

calibration curve. Subsequent analyses of the PT samples on multiple testing days were then used to calculate 

the accuracy of the CT-1128 measurements. To measure the potential matrix effects on the CT-1128 in 

selected real-world applications, it was challenged by analyzing samples fortified with the target contaminant 

in various matrices including drinking water (DW) samples (which varied in source and treatment), a weakly 

buffered water sample, a strongly buffered water sample, and a trihalomethanes (THMs)-fortified water 

sample. The concentration of a mid-level PT sample was used to fortify the matrix samples. This 

concentration provided a convenient level that was approximate to or below the concentration of interest for 

the target contaminants. 

In addition to the PT, DW, buffered waters, and THMs-fortified water samples, blanks and unfortified matrix 

samples were analyzed to confirm negative responses in the absence of target contaminants and also to ensure 

that no sources of contamination were introduced during the analysis. 

Experienced GC-MS operators were used for testing since the vendor suggests that a new user obtain training 

in the use of a GC-MS prior to operating the CT-1128. The vendor identified solid phase microextraction 

(SPME) as the technique for preparing the water samples for subsequent GC-MS analysis by the CT-1128. It 

is very important to note that the methodology provided by the vendor was not optimized for any one specific 

target chemical. The same SPME fiber type and GC column were used throughout the test for all analytes. 
QA oversight of verification testing was provided by Battelle and EPA. Battelle QA staff conducted a 

technical systems audit, a performance evaluation audit, and a data quality audit of 10% of the test data. This 

verification statement, the full report on which it is based, and the test/QA plan for this verification test are all 

available at www.epa.gov/etv/centers/center1.html. 

TECHNOLOGY DESCRIPTION 

The following description of the CT-1128 is based on information provided by the vendor. This technology 

description was not verified in this test. 

The CT-1128 analyzes, on-site, known and unknown chemicals. The CT-1128 is a lightweight, ruggedized, 

field deployable GC-MS system that can accommodate the applications of traditional laboratory based GCMS systems. With the appropriate extraction techniques, analysis may be performed on a variety of matrices 

including DW, which can be prepared using SPME. 

The CT-1128 weighs approximately 75 pounds (34 kilograms) and is 15 inches (38.1 cm) by 23 inches (58.4 

cm) by 15 inches (38.1 cm). It is contained in a carrying case housing the entire system. The CT-1128 has a 

range of 1.6 to 800 atomic mass units with unit resolution throughout the mass range. In selected ion mode 

(SIM), the CT-1128 can scan for 50 groups of masses with 30 masses per group. For identification of 

chemicals, the CT-1128 is equipped with an automated mass spectral data base searching function that can 

use a range of commercial mass spectral libraries (e.g., National Institute of Standards and Technology Mass 

Spectral Library) as well as user-defined libraries. The system is controlled with a laptop computer that uses a 

program for GC control and MSD Chemstation (Agilent Technologies) for MS control and data analysis. 

The CT-1128, which requires ultra-high purity hydrogen or helium (or nitrogen if desired) for the carrier gas, 

can use either an external gas tank or its on-board hydrogen storage bottle. The metal hydride storage bottle 

can be charged with hydrogen to provide a source of carrier gas that is convenient for mobile operation. The 

mass spectrometer can be tuned using an internal calibrant such as perfluorotributylamine (PFTBA) to 

perform a standard spectra tune or autotune (for maximum sensitivity over the entire scanning range) 

depending on the user’s needs. At the time of testing, the cost of the CT-1128 GC-MS system, with optional 

SPME stirrer/heater, was $140,000. 

VERIFICATION RESULTS 

Summary of Accuracy, Precision, Linearity, and Stability 

Contaminant 

Accuracy Precision Linearity Stability 

Mean 

Percent 

Recovery 

(R) 

Mean 

Relative 

Standard 

Deviation 

(RSD) 

Coefficient of 

Determination 

of Curve (r2

) 

Mean 

Relative 

Percent 

Difference 

(RPD) 

benzene 172% 10% 1.000 27% 

toluene 440% 43% 1.000 52% 

ethylbenzene 104% 16% 1.000 9% 

xylenes (total) 103% 10% 1.000 12% 

2,4-D 62% 21% 0.921 35% 

dicrotophos 143% 42% 0.999 92% 

GB 108% 24% 1.000 48% 

GD 75% 14% 1.000 27% 

VX 109% 15% 0.959 27% 
Benzene accuracy was considerably higher than ideal (100%) at 172% recovery (R) because of a change in 

response several days after establishing the calibration curve. Toluene exhibited significant over-recoveries, 

with an overall mean R of 440%, though accuracy for ethylbenzene and xylenes (total) was close to 100%. 

The mean R for 2,4-D and dicrotophos was 62% and 143%, respectively. For GB, the accuracy was close to 

ideal at 108%. For GD, R was acceptable at 75. The mean R for VX was 109%, though the concentrations 

tested were significantly higher than the LD50 for this agent. Precision, as measured by relative standard 

deviation (RSD) of replicate samples, ranged from 10% for benzene to 43% for toluene. 

In regard to linearity, the calibration curves of seven of the nine contaminants had coefficients of 

determination (r2

) of 0.999 or greater. The exceptions were those contaminants for which the provided method 

lacked sensitivity—2,4-D and VX (r2

 of 0.921 and 0.959, respectively), though for all contaminants, r2 values 

were greater than 0.920. Instrument stability was evaluated by comparing the results of mid-level PT samples 

at the beginning and end of the testing day and determining relative percent difference (RPD) of the PT 

samples (ideal RPD is 0%). Stability results ranged from 9% RPD for ethylbenzene to 92% for dicrotophos. 

Only two contaminants, ethylbenzene and xylenes (average RPD of 9% and 12%, respectively), had average 

RPDs less than 20%, while toluene and dicrotophos had RPDs significantly greater than 20% (52% and 92%, 

respectively). 

Summary of Matrix Effects Observed 

Contaminant 

Matrix Effect(a) from Potential Interferents 9 = observed 

DW1 DW2 DW3 DW4 

Weakly 

Buffered 

Water 

Strongly 

Buffered 

Water 

THMs 

Spiked 

Water 

benzene • • 

toluene • • • • 

ethylbenzene • 

xylenes • 

2,4-D • • • • • 

dicrotophos • • • • • 

GB • • • 

GD • • • • • 

VX ND ND ND ND ND ND ND 

(a) matrix effect defined as recovery ± 30% of average response of daily PT samples fortified at the same concentration 

ND = no data; VX matrix testing was not performed due to lack of sensitivity for this contaminant using the vendor-provided method 

A matrix effect was present with the strong buffer matrix, which gave R values outside the 70% to 130% 

range for all eight of the target contaminants tested. DW3 also showed matrix effects for five of the eight 

contaminants, which may be due to its origin as a groundwater sample. 
With the exception of VX and 2,4-D (for which the provided methods lacked sensitivity), the sensitivity of the 

CT-1128 was sufficient to detect the target contaminants at the concentrations of interest (i.e., LD50 or MCL 

concentrations). 

Results of CT-1128 Sensitivity Testing for Target Contaminants 

Contaminant 

Concentration 

of Interest 

(mg/L) 

Sufficient Sensitivity 

to Detect Conc. of 

Interest 

benzene 0.005 Yes 

toluene 1 Yes 

ethylbenzene 0.7 Yes 

xylenes (total) 10 Yes 

2,4-D 0.07 No 

dicrotophos 1400 Yes 

GB 20 Yes 

GD 1.4 Yes 

VX 2.1 No 

Field portability and operational factors: Because the CT-1128 requires time for thermal equilibration once 

electrical power and gas have been supplied, it should be kept on standby (under vacuum and thermally 

equilibrated) as long as possible when time is a critical factor for analyzing field samples. Mobilization in the 

field is straightforward, and the CT-1128 requires only a source of electrical power for several hours of field 

deployment when used with its on-board hydrogen canister for a source of carrier gas. Typical extraction and 

sample run times ranged from 22 minutes to 32 minutes. Average sample throughput during verification 

testing was 11 samples per 10-hour working day, or approximately one sample per hour. For 100 samples, the 

total cost for supplies was approximately $914, not including the GC column and standard chemicals. 

Original signed by Gregory A. Mack 5/24/06 Original signed by Andrew P. Avel 7/3/06 

Gregory A. Mack Date Andrew P. Avel Date 

Vice President Acting Director 

Energy, Transportation, and Environment Division National Homeland Security Research Center 

Battelle Office of Research and Development 

U.S. Environmental Protection Agency 

NOTICE: ETV verifications are based on an evaluation of technology performance under specific, 

predetermined criteria and the appropriate quality assurance procedures. EPA and Battelle make no expressed or 

implied warranties as to the performance of the technology and do not certify that a technology will always 

operate as verified. The end user is solely responsible for complying with any and all applicable federal, state, 

and local requirements. Mention of commercial product names does not imply endorsement. 
May 2006 

Environmental Technology Verification 

Report

ETV Advanced Monitoring Systems Center 

Constellation Technology Corporation 

CT-1128 Portable 

Gas Chromatograph-Mass Spectrometer 

by

Raj Mangaraj 

Amy Dindal

Zachary Willenberg

Karen Riggs

Battelle 

Columbus, Ohio 43201
Notice 

The U.S. Environmental Protection Agency (EPA), through its Office of Research and 

Development, has financially supported and collaborated in the extramural program described 

here. This document has been peer reviewed by the Agency. Mention of trade names or 

commercial products does not constitute endorsement or recommendation by the EPA for use. 

ii 
Foreword

The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the 

nation’s air, water, and land resources. Under a mandate of national environmental laws, the 

Agency strives to formulate and implement actions leading to a compatible balance between 

human activities and the ability of natural systems to support and nurture life. To meet this 

mandate, the EPA’s Office of Research and Development provides data and science support that 

can be used to solve environmental problems and to build the scientific knowledge base needed 

to manage our ecological resources wisely, to understand how pollutants affect our health, and to 

prevent or reduce environmental risks. 

The Environmental Technology Verification (ETV) Program has been established by the EPA to 

verify the performance characteristics of innovative environmental technology across all media 

and to report this objective information to permitters, buyers, and users of the technology, thus 

substantially accelerating the entrance of new environmental technologies into the marketplace. 

Verification organizations oversee and report verification activities based on testing and quality 

assurance protocols developed with input from major stakeholders and customer groups 

associated with the technology area. ETV consists of six environmental technology centers. 

Information about each of these centers can be found on the Internet at http://www.epa.gov/etv/. 

Effective verifications of monitoring technologies are needed to assess environmental quality 

and to supply cost and performance data to select the most appropriate technology for that 

assessment. Under a cooperative agreement, Battelle has received EPA funding to plan, 

coordinate, and conduct such verification tests for “Advanced Monitoring Systems for Air, 

Water, and Soil” and report the results to the community at large. Information concerning this 

specific environmental technology area can be found on the Internet at http://www.epa.gov/etv/ 

centers/center1.html. 

iii 
Acknowledgments

The authors wish to acknowledge the support of all those who helped plan and conduct the 

verification test, analyze the data, and prepare this report. Many thanks go to Battelle’s 

Hazardous Materials Research Center for providing the facilities for and personnel capable of 

working with chemical warfare agents. We sincerely appreciate the contribution of drinking 

water samples from the Metropolitan Water District of Southern California (Paul Rochelle and 

Melinda Stalvey), The New York Department of Environmental Protection (Virginia Murray), 

and Orange County Utilities, Orlando, Florida (Theresa Slifko and Liza Robles). We would also 

like to thank Matthew Magnuson (US EPA, National Homeland Security Research Center), Lisa 

Olsen (U.S. Geological Survey), Victor Silvestri (New York City Department of Environmental 

Protection) and Lynn Wright (US EPA, National Exposure Research Laboratory) for their 

careful review of the test/quality assurance plan and this verification report. 

iv 
Contents 

Page 

Notice ................................................................................................................................. ii 

Foreword ................................................................................................................................ iii 

Acknowledgments ....................................................................................................................... iv

List of Abbreviations................................................................................................................. viii 

Chapter 1 Background ................................................................................................................. 1 

Chapter 2 Technology Description .............................................................................................. 2 

Chapter 3 Test Design ................................................................................................................. 5 

3.1 Test Samples.............................................................................................................. 6 

3.1.1 Performance Test (PT) Samples ...................................................................... 6 

3.1.2 Potential Matrix and Interference Effects Samples .......................................... 7 

3.1.3 Quality Control Samples............................................................................... 10 

3.2 Testing Procedure .................................................................................................... 10 

3.2.1 Laboratory Testing ......................................................................................... 10 

3.2.2 Non-Laboratory Testing ................................................................................ 12 

3.3 Reference Methods .................................................................................................. 12 

3.3.1 CWA Reference Method ............................................................................... 13 

3.3.2 Pesticide Reference Method .......................................................................... 13 

3.3.3 BTEX Reference Method .............................................................................. 13 

Chapter 4 Quality Assurance Quality Control ........................................................................... 14 

4.1 Audits....................................................................................................................... 15 

4.1.1 Performance Evaluation Audit....................................................................... 15 

4.1.2 Technical Systems Audit ............................................................................... 16 

4.1.3 Audit of Data Quality .................................................................................... 16 

4.2 QA/QC Reporting .................................................................................................... 16 

4.3 Data Review............................................................................................................. 16

Chapter 5 Statistical Methods and Reported Parameters............................................................ 18 

5.1 Accuracy.................................................................................................................. 18 

5.2 Precision .................................................................................................................. 18 

5.3 Linearity................................................................................................................... 19 

5.4 Sensitivity ................................................................................................................ 19 

5.5 Instrument Stability.................................................................................................. 19 

5.6 Potential Matrix and Interference Effects................................................................. 20 

5.7 Field Portability ....................................................................................................... 20

5.8 Operational Factors.................................................................................................. 20 

Chapter 6 Test Results............................................................................................................... 21 

6.1 Accuracy.................................................................................................................. 21 

6.2 Precision .................................................................................................................. 26 

6.3 Linearity................................................................................................................... 27 

6.4 Sensitivity ................................................................................................................ 32 

v 
6.5 Instrument Stability.................................................................................................. 32 

6.6 Potential Matrix and Interference Effects................................................................. 33 

6.7 Field Portability ....................................................................................................... 34

6.8 Operational Factors.................................................................................................. 36 

Chapter 7 Performance Summary.............................................................................................. 38 

Chapter 8 References................................................................................................................. 41 

Figures 

Figure 2-1. Constellation Technology Corporation CT-1128 Portable GC-MS.......................... 4 

Figure 6-1a. Library Match for GB without Background Subtraction ........................................ 24 

Figure 6-1b. Library Match for GB with Background Subtraction ............................................. 25 

Figure 6-2a. Calibration Curve for Benzene............................................................................... 28 

Figure 6-2b. Calibration Curve for Toluene ............................................................................... 28 

Figure 6-2c. Calibration Curve for Ethylbenzene....................................................................... 29 

Figure 6-2d. Calibration Curve for Xylenes (Total).................................................................... 29 

Figure 6-2e. Calibration Curve for 2,4-D ................................................................................... 30 

Figure 6-2f. Calibration Curve for Dicrotophos......................................................................... 30 

Figure 6-2g. Calibration Curve for GB....................................................................................... 31 

Figure 6-2h. Calibration Curve for GD....................................................................................... 31 

Figure 6-2i. Calibration Curve for VX....................................................................................... 32 

Figure 6-3. Use and Installation of CT-1128 Outside of the Laboratory................................... 35 

Tables 

Table 2-1. CT-1128 Technical Specifications (from Constellation Technology Corporation)(a) 4 

Table 3-1. Target Contaminants and Concentrations of Interest................................................ 6 

Table 3-2. Performance Test Sample Solution Concentrations for Target Contaminants.......... 7 

Table 3-3. Potential Matrix and Interference Spiking Concentrations....................................... 8 

Table 3-4. Treatment and Source Characteristics of Drinking Water Samples .......................... 8 

Table 3-5. Physio-Chemical Characterization of Drinking Water Samples............................... 9 

Table 3-6. CT-1128 Analytical Methods for Target Contaminants ......................................... 11 

Table 3-7. Reference Methods for Target Contaminants......................................................... 12 

Table 4-1. Changes to Test/QA Plan for Verification of Mobile Mass Spectrometers............. 14 

Table 4-2. Summary of Reference Measurement Percent Recovery (R) ................................. 15 

vi 
Table 4-3. Summary of Data Recording Process..................................................................... 17 

Table 6-1a. Accuracy (Percent Recovery) Results – Benzene................................................... 22 

Table 6-1b. Accuracy (Percent Recovery) Results – Toluene ................................................... 22 

Table 6-1c. Accuracy (Percent Recovery) Results – Ethylbenzene........................................... 22 

Table 6-1d. Accuracy (Percent Recovery) Results – Xylenes (Total) ....................................... 23 

Table 6-1e. Accuracy (Percent Recovery) Results – 2,4-D and Dicrotophos ............................ 23 

Table 6-1f. Accuracy (Percent Recovery) Results – GB and GD ............................................. 23 

Table 6-1g. Accuracy (Percent Recovery) Results – VX........................................................... 26 

Table 6-2. Summary of RSD of the Various Sample Types(a) ................................................. 26 

Table 6-3. Summary of Calibration Curve Data...................................................................... 27 

Table 6-4. Sensitivity of CT-1128........................................................................................... 32 

Table 6-5. Results of Stability Testing for CT-1128 ............................................................... 33 

Table 6-6. Results of Potential Matrix and Interference Effects............................................... 34 

Table 6-7. Field Portability Results......................................................................................... 36

Table 7-1. Summary of Accuracy, Precision, Linearity, and Stability ..................................... 38 

Table 7-2. Summary of Matrix Effects Observed .................................................................... 39 

Table 7-3. Results of CT-1128 Sensitivity Testing for Target Contaminants........................... 39 

vii 
List of Abbreviations 

AMS Advanced Monitoring Systems 

ASTM American Society for Testing and Materials 

BTEX benzene, toluene, ethylbenzene, and xylenes 

CWA chemical warfare agent 

DW drinking water 

EI electron impact 

EPA U.S. Environmental Protection Agency 

ETV Environmental Technology Verification 

GC-MS gas chromatograph-mass spectrometer 

kg kilogram 

m meter 

MCL maximum contaminant level 

mg milligram 

μMHO micromhos 

mL milliliter 

NaCl sodium chloride 

R recovery (percent) 

PE performance evaluation 

PFTBA perfluorotributylamine 

ppb part per billion 

ppm part per million 

psi pounds per square inch 

PT performance test 

QA quality assurance 

QC quality control 

QMP quality management plan 

RPD relative percent difference 

RSD relative standard deviation 

SIM selected ion mode 

SPME solid phase microextraction 

THMs trihalomethanes 

TIC total ion chromatogram 

TSA technical systems audit 

viii 
Chapter 1

Background 

The U.S. Environmental Protection Agency (EPA) supports the Environmental Technology 

Verification (ETV) Program to facilitate the deployment of innovative environmental 

technologies through performance verification and dissemination of information. The goal of the 

ETV Program is to further environmental protection by accelerating the acceptance and use of 

improved and cost-effective technologies. ETV seeks to achieve this goal by providing highquality, peer-reviewed data on technology performance to those involved in the design, 

distribution, financing, permitting, purchase, and use of environmental technologies. 

ETV works in partnership with recognized testing organizations; with stakeholder groups 

consisting of buyers, vendor organizations, and permitters; and with the full participation of 

individual technology developers. The program evaluates the performance of innovative 

technologies by developing test plans that are responsive to the needs of stakeholders, 

conducting field or laboratory tests (as appropriate), collecting and analyzing data, and preparing 

peer-reviewed reports. All evaluations are conducted in accordance with rigorous quality 

assurance (QA) protocols to ensure that data of known and adequate quality are generated and 

that the results are defensible. 

The EPA’s National Exposure Research Laboratory and its verification organization partner, 

Battelle, operate the Advanced Monitoring Systems (AMS) Center under ETV. The AMS Center 

recently evaluated the performance of the Constellation Technology Corporation CT-1128 

Portable Gas Chromatograph-Mass Spectrometer (GC-MS). Mobile mass spectrometers were 

identified as a priority technology verification category through the AMS Center stakeholder 

process. 

1 
Chapter 2

Technology Description 

The objective of the ETV AMS Center is to verify the performance characteristics of 

environmental monitoring technologies for air, water, and soil. This verification report provides 

results for the verification testing of the CT-1128 Portable GC-MS. Following is a description of 

CT-1128, based on information provided by the vendor, Constellation Technology Corporation. 

The information provided below was not verified in this test. 

The CT-1128 (Figure 2-1) 

analyzes, on-site, known 

and unknown chemicals. 

The CT-1128 is a 

lightweight, ruggedized, 

field deployable GC-MS 

system that can 

accommodate the 

applications of traditional 

laboratory based GC-MS 

systems. With the appropriate extraction techniques, analysis may be 

performed on a variety of 

matrices including drinking 

water (DW), which can be 

prepared using solid phase 

microextraction (SPME). 

Technical specifications of the CT-1128 are presented in Table 2-1. The CT-1128 weighs 

approximately 75 pounds (34 kg) and is 15 inches (38.1 cm) by 23 inches (58.4 cm) by 15 inches 

(38.1 cm). It is contained in a carrying case housing the entire system. The CT-1128 has a range 

of 1.6 to 800 atomic mass units with unit resolution throughout the mass range. In selected ion 

mode (SIM), the CT-1128 can scan for 50 groups of masses with 30 masses per group. For 

identification of chemicals, the CT-1128 is equipped with an automated mass spectral data base 

searching function that can use a range of commercial mass spectral libraries (e.g., National 

Institute of Standards and Technology Mass Spectral Library) as well as user-defined libraries. 

Figure 2-1. Constellation Technology Corporation CT-1128 

Portable GC-MS 

2 
The system is controlled with a laptop computer that uses a program for GC control and MSD 

Chemstation (Agilent Technologies) for MS control and data analysis. 

The CT-1128, which requires ultra-high purity hydrogen or helium (or nitrogen if desired) for 

the carrier gas, can use either an external gas tank or its on-board hydrogen storage bottle. The 

metal hydride storage bottle can be charged with hydrogen to provide a source of carrier gas that 

is convenient for mobile operation. The mass spectrometer can be tuned using an internal 

calibrant such as perfluorotributylamine (PFTBA) to perform a standard spectra tune or autotune 

(for maximum sensitivity over the entire scanning range) depending on the user’s needs. At the 

time of testing, the cost of the CT-1128 GC-MS system, with optional SPME stirrer/heater, was 

$140,000. 

3 
Table 2-1. CT-1128 Technical Specifications (from Constellation Technology 

Corporation)(a) 

INSTRUMENT PARAMETER SPECIFICATION 

Gas Chromatograph 

GC Injection Port Varian, model CP-1177; direct injection 

GC Oven Ramp Speed Up to 60°C/min to 325°C 

GC Oven / Injection Port Temperature Range Ambient to 325°C, oven with double ramp capability 

Carrier Gas Pressure Capacity < 200 pounds per square inch (psi) at gas inlet, 0-40 psi variable 

head pressure to control carrier gas flow through column 

Carrier Gas Compatibility Helium, hydrogen, or nitrogen 

Carrier Gas Source Internal hydrogen bottle (~160 operating hours) or external gas 

tank (He, H2, N2 (although N2 is rarely used)) 

Injection Mode Split or splitless 

GC Column Available from a variety of GC column vendors including 

Quadrex Corp. 

Mass Spectrometer 

Quadrupole Mass Spectrometer Agilent Technologies, model 5973N MSD 

Mass Range Capability 1.6 – 800 m/z, 0.1 m/z steps 

Mass Resolution Unit mass resolution throughout mass range 

Scan Speed Up to 10,400 amu per second 

Detector Dynamic Range Total analog/digital converter (ADC) = 106 

Mass Axis Stability ±0.15 amu over 12 hours 

SIM Capability Up to 50 groups of masses, with 30 masses per group, can be 

varied throughout a run 

SIM Dwell Time 10 – 9,999 msec/mass 

Ionization Mode/Energy/Current EI (electron impact), voltage/current user-selectable (5-240 eV), 

dual filaments 

Ion Source Temperature Up to 250°C for EI 

Quadrupole Temperature Up to 200°C, independent of ion source 

EI SIM Sensitivity RMS signal/noise ratio at 272.0 m/z > 10:1 for 20 fg 

octafluoronaphthalene 

Software MSD Chemstation 

MS Data Base National Institute of Standards and Technology/EPA/National 

Institutes of Health comprehensive library 

MS Tuning Capability Multiple autotune algorithms available, compound-specific 

autotunes available for PFTBA, BFB, DFTPP, etc 

CT-1128 GC-MS System 

Dimensions (L x W x H) 38.1 cm x 58.4 cm x 38.1 cm (15” x 23” x 15”) 

Weight ~ 34 kg (75 pounds) 

Operating Conditions 10-35°C, 5-95% humidity 

Power Requirements 99-127 volts, single phase; A/C; 48-66 Hz 

Vacuum System 1 Diaphragm rough pump, 2 turbomolecular pumps 

Operating System Windows 2000 

Detection Limits ~100 pg hexachlorobenzene; most compounds have detection 

limits in the picogram range assuming scanning ion mode 

(a) these specifications were not verified during testing; analytical conditions used during testing are provided in 

Chapter 3 

4 
 Chapter 3 

Test Design 

Many volatile and semivolatile contaminants in water are detected using bench-top mass 

spectrometers in a traditional laboratory setting. However, the CT-1128 verified in this test was a 

portable unit designed to be taken outside the laboratory setting for field analysis. This 

portability offers an advantage to first-responders and other users who need chemical 

information when time, sampling, and other limitations preclude analysis in a laboratory. 

This verification was conducted from September through December 2005 according to 

procedures specified in the Test/QA Plan for Verification of Mobile Mass Spectrometer. (1) The 

ability of the CT-1128 to identify and quantify target contaminants was tested in various water 

matrices. The CT-1128 was evaluated for the following performance parameters: 

• Accuracy 

• Precision 

• Linearity 

• Instrument stability 

• Potential matrix and interference effects 

• Sensitivity 

• Field portability 

• Operational factors. 

The testing was conducted on the contaminants listed in Table 3-1. Three classes of 

contaminants were tested: volatile organic compounds (benzene, toluene, ethyl benzene, total 

xylenes (BTEX)), pesticides (2,4-D and dicrotophos), and chemical warfare agents (VX, GB, 

and GD). The contaminants were selected based on recommendations from the AMS Center 

stakeholders. 

5 
Table 3-1. Target Contaminants and Concentrations of Interest 

Contaminant CAS#(a) LD50 (mg/L)(b) Maximum Contaminant Level (mg/L)(c) 

VX 50782-69-9 2.1 NA 

GB (sarin) 107-44-8 20 NA 

GD (soman) 96-64-0 1.4 NA 

dicrotophos 141-66-2 1,400 NA 

2,4-D 94-75-7 NA 0.07 

benzene 71-43-2 NA 0.005 

toluene 108-88-3 NA 1 

ethylbenzene 100-41-4 NA 0.7 

xylenes (total) 1330-20-7 NA 10 

(a) Chemical Abstracts Number 

(b) LD50 values assume a 70-kilogram individual consuming 250 milliliters (mL) of the contaminated water 

(c) Maximum Contaminant Level (MCL) as defined by EPA National Primary Drinking Water Regulations 

NA = Not applicable 

3.1 Test Samples 

Samples were prepared daily from stock solutions to minimize loss of target contaminants due to 

hydrolysis. For chemical warfare agent (CWA) testing, a stock solution containing both GB and 

GD and another containing VX only were prepared in acetone. Stock solutions for the other 

contaminants, one containing all BTEX compounds and another containing both 2,4-D and 

dicrotophos, were prepared in methanol to minimize degradation. Each of the test sample types 

are described in detail in this section. 

3.1.1 Performance Test (PT) Samples 

The performance test (PT) samples were prepared in American Society for Testing and Materials 

(ASTM) Type II water. Table 3-2 shows the concentrations of the PT samples that were analyzed 

for the target contaminants. The target contaminant concentrations were constructed to cover or 

approximate the concentrations of interest presented in Table 3-1. The concentrations of interest 

were calculated using LD50 values assuming a 70-kilogram individual consuming 250 milliliters 

(mL) of the contaminated water. When LD50 data were not available or feasible for testing, MCL 

values, as defined by EPA National Primary Drinking Water Regulations, were used. For 2,4-D 

and VX, the levels of interest in Table 3-1 could not be reached due to the sensitivity of the 

analytical methods provided by the vendor. For these contaminants, concentrations with 

adequate instrumental response were determined and used for verification testing. Reference 

measurements were conducted on PT samples only, to confirm the accuracy of sample 

preparation. To avoid discrepancies due to contaminant degradation, reference measurements 

were made as close as possible in time with the measurements made with the CT-1128. 

6 
Table 3-2. Performance Test Sample Solution Concentrations for Target Contaminants 

Class Contaminant 

PT Sample 

1 

(mg/L) 

PT Sample 

2 

(mg/L) 

PT Sample 

3 

(mg/L) 

PT Sample 

4 

(mg/L) 

PT Sample 

5 

(mg/L) 

VX 10 15 30 NA NA 

CWA GB 0.5 1 10 NA NA 

GD 0.5 1 10 NA NA 

Pesticide dicrotophos 5 50 500 1,000 NA 

2,4-D 0.5 5 50 75 100 

benzene 0.01 0.1 1 10 NA 

BTEX toluene 0.001 0.01 0.1 1 NA 

ethylbenzene 0.001 0.01 0.1 1 NA 

xylenes (total) 0.001 0.01 0.1 1 NA 

NA = Not applicable. 

The PT samples were used to determine the accuracy of the CT-1128. One set of these PT 

samples was used to establish a calibration curve. Subsequent analyses of the PT samples on 

multiple testing days were then used to calculate the accuracy of the CT-1128 measurements. 

Three replicate measurements were made for each PT sample for the accuracy testing, with the 

exception of 2,4-D and dicrotophos. As shown in Tables 3-1 and 3-2, the tested concentrations 

were considerably higher and lower than the levels of interest for 2,4-D and dicrotophos, 

respectively, due to the analytical sensitivity of the CT-1128. Since a great deal of effort was 

invested in determining the appropriate concentration levels for 2,4-D and dicrotophos, only one 

replicate of each pesticide PT sample concentration was analyzed in order to analyze the rest of 

the test samples prior to CWA testing. 

3.1.2 Potential Matrix and Interference Effects Samples 

To measure the potential matrix effects on the CT-1128 in selected real-world applications, it 

was challenged by analyzing samples fortified with the target contaminant in various matrices 

including regional DW samples, a weakly buffered water sample, a strongly buffered water 

sample, and a trihalomethanes (THMs)-fortified water sample as shown in Table 3-3. The 

concentration of a mid-level PT sample was used to fortify the matrix samples. This 

concentration provided a convenient level that was at or below the concentration of interest for 

most of the target contaminants. As shown in Table 3-3, matrix and interference effects were not 

evaluated for VX, due to the relatively low sensitivity for this contaminant with the testing 

methodology. 

7 
Table 3-3. Potential Matrix and Interference Spiking Concentrations 

Sample Type 

Fortified Concentration in Solution (mg/L) 

Benzene 

Toluene, 

Ethylbenzene, 

Xylenes 

2,4-D Dicrotophos GB, 

GD VX(a) 

DW1(b) 1 0.1 50 500 1 NA 

DW2(b) 1 0.1 50 500 1 NA 

DW3(b) 1 0.1 50 500 1 NA 

DW4(b) 1 0.1 50 500 1 NA 

Weakly Buffered 

Water (442-30)(c) 1 0.1 50 500 1 NA 

Strongly Buffered 

Water (442-3000)(c) 1 0.1 50 500 1 NA 

THMs Spiked Water 

(ASTM Type II 

Water)(c) 

1 0.1 50 500 1 NA 

(a) VX testing was limited due to lack of sensitivity for this contaminant using the vendor-provided method. 

NA = Not applicable. 

(b) See Section 3.1.2.1 for identification of DW sources. 

(c) See Section 3.1.2.2 for a description of these samples. 

3.1.2.1 Drinking Water Samples 

DW samples were collected from four geographically distributed municipal sources to evaluate 

the performance of the CT-1128 with various sample matrices. These finished DW samples 

varied in their source, treatment, and disinfection process. All samples underwent either 

chlorination or chloramination disinfection prior to receipt. Samples were collected from water 

utility systems with the treatment and source characteristics listed in Table 3-4. 

Table 3-4. Treatment and Source Characteristics of Drinking Water Samples 

Drinking Water 

ID Water Utility Water 

Treatment 

Source 

Type 

DW1 Columbus, Ohio 

(OH) chlorinated filtered surface 

DW2 New York City, New York (NY) chlorinated 

unfiltered surface 

DW3 Orlando, Florida 

(FL) chlorinated filtered ground 

DW4 Metropolitan Water District of Southern California 

(CA) 

chloraminated 

filtered surface 

All samples were collected in pre-cleaned high density polyethylene containers. After sample 

collection, to characterize the DW matrix, an aliquot of each DW sample was sent to a 

subcontract laboratory to determine the following water quality parameters: concentration of 

THM, haloacetic acids, total organic halides, pH, conductivity, alkalinity, turbidity, organic 

carbon, and hardness (see Table 3-5 for results of these analyses). 

8 
Table 3-5. Physio-Chemical Characterization of Drinking Water Samples 

Sources of Drinking Water Samples 

Parameter Unit Method 

Columbus, 

OH 

(DW1) 

New York 

City, NY 

(DW2) 

Orlando, 

FL 

(DW3) 

MWD(b), 

CA 

(DW4) 

Turbidity NTU(a) EPA 180.1(2) 0.1 1.1 0.5 0.1 

Dissolved Organic 

Carbon mg/L SM 5310(3) 2.1 1.1 1.6 2.9 

Total Organic 

Carbon mg/L SM 5310(3) 2.1 1.6 1.7 2.5 

Specific 

Conductivity μMHO SM 2510(3) 572 84 322 807 

Alkalinity mg/L SM 2320(3) 40 14 142 71 

pH EPA 150.1(4) 7.6 6.9 8.5 8.0 

Calcium mg/L EPA 200.8(5) 33 5.6 8.8 45 

Magnesium mg/L EPA 200.8(5) 7.7 1.3 43 20 

Hardness mg/L EPA 130.2(6) 118 20 143 192 

Total Organic 

Halides μg/L SM 5320(3) 220 82 300 170 

Trihalomethanes μg/L/analyte EPA 524.2(7) 74.9 39.0 56.4 39.2 

Haloacetic Acids μg/L/analyte EPA 552.2(8) 32.8 39.0 34.6 17.4 

(a) NTU = Nephelometric turbidity unit. 

(b) MWD = Metropolitan Water District of Southern California 

Because free chlorine degrades many of the target contaminants and interferents during storage, 

the DW samples were immediately dechlorinated with sodium thiosulfate pentahydrate upon 

arrival at Battelle. The dechlorination of the DW was qualitatively confirmed by adding a 

diethyl-p-phenylene diamine tablet to an aliquot of the DW. If the water did not turn pink, the 

dechlorination process was determined to be successful. If the water did turn pink, an additional 

dechlorinating reagent was added and the dechlorination confirmation procedure was repeated. 

The bulk DW samples were dechlorinated upon arrival and did not require any additional 

dechlorination during testing. 

3.1.2.2 Weakly Buffered, Strongly Buffered, and Trihalomethanes Matrices 

The effect of ionic strength on the response of the CT-1128 was examined. Since natural water 

salt type and concentration can vary greatly by location, two sample types were fortified at a mid 

level PT sample concentration in 442 Natural WaterTM Standard Solution (Myron L Instruments, 

Carlsbad, CA). Two 442 solutions, 442-30 and 442-3000, containing 21.8 parts-per-million 

(ppm) sodium chloride (NaCl) and 2,027 ppm NaCl, respectively, were used for this purpose. 

The CT-1128 was also challenged by the presence of potential interferents. THMs are typically 

observed at low levels in DW as by-products of the disinfection process. Four THMs 

(chloroform, bromoform, bromodichloromethane, and dibromochloromethane) were spiked into 

a midlevel PT sample at 80 parts per billion (ppb) total, which is the MCL for total THMs as 

9 
defined in EPA’s National Primary Drinking Water Regulations. (12) Chloroform, bromoform, 

bromodichloromethane, and dibromochloromethane were spiked so that their concentrations in 

solution were 50, 5, 15, and 10 ppb, respectively, to represent typical ratios of THMs in finished 

DW. 

3.1.3 Quality Control Samples 

In addition to the PT, DW, buffered water, and THMs-fortified water samples, blanks and 

unfortified matrix samples were analyzed to confirm negative responses in the absence of target 

contaminants and also to ensure that no sources of contamination were introduced during the 

analysis. 

3.2 Testing Procedure 

3.2.1 Laboratory Testing 

Experienced GC-MS operators were used for testing since the vendor suggests that a new user 

obtain training in the use of a GC-MS prior to operating the CT-1128. All of the operators were 

trained laboratory staff and were experienced in the proper use and handling of laboratory 

chemicals. Additionally, analyses of CWAs were handled by staff trained with specific skills 

necessary for working in a CWA laboratory. 

The vendor provided a sample preparation technique as well as analytical methodology for the 

three groups of contaminants to be analyzed during the verification test: BTEX, pesticides, and 

CWAs. Ultra-high purity (UHP) helium was used for the carrier gas. The vendor identified 

SPME as the technique for preparing the water samples for subsequent GC-MS analysis by the 

CT-1128. SPME is a relatively simple adsorption/desorption technique for extracting volatile and 

semivolatile chemicals from a liquid sample or headspace. The technique employs the use of a 

fused silica fiber that is coated with a polymer. The specific SPME fiber should be chosen based 

on the application of interest. It is very important to note that the methodology provided by the 

vendor was not optimized for any one specific target chemical. The same SPME fiber type and 

GC column were used throughout the test for all analytes. The SPME fiber was replaced 

approximately after every 50 extractions or at the discretion of the operator. Therefore, further 

optimization of the extraction and separation/detection process may be possible. 

The provided methodology specified daily check procedures that were followed each day before 

the analysis of samples. These procedures included diagnostic checks for system operation (e.g., 

check of MS vacuum and temperature of heated zones), tuning of the MS, and column/SPME 

fiber bakeout. The CT-1128 was mass tuned using PFTBA (as the internal calibrant) and the 

autotune function. It should be noted that the method provided by the vendor originally specified 

that the operator should perform MS autotune on a daily basis. According to the vendor, their 

typical users, who are seeking a qualitative rather than quantitative result, start up and shut down 

the CT-1128 on a regular basis as they transport the instrument from site to site. Since the 

quantity of a particular contaminant may be a critical factor in determining the appropriate 

corrective action(s), this verification test focused on the quantitative abilities of the mobile mass 

spectrometer. For the verification test, the CT-1128 ran continuously once it was installed in a 

10 
particular location. Since the autotune function will change the MS settings, any quantitative 

data obtained after an autotune may not compare well to such data obtained prior to the autotune. 

Since the operator intended to obtain one calibration curve and use it to quantify the results of 

several days of subsequent testing, the vendor suggested performing an autotune only if the CT1128 had been shut down and restarted after a period of two hours or more. This change in the 

methodology was requested by the vendor when the Verification Test Coordinator inquired about 

the variation in instrument response over the course of several days of testing. 

Table 3-6 summarizes the instrumental parameters for each of the three methods provided. 

Testing solutions were prepared daily from stock solutions. To an empty vial, 15 mL of a test 

water sample and a disposable magnetic stirbar were added before capping and crimping a seal 

onto the vial. For all of the target contaminants analyzed in the verification test, the vendor 

provided Supelco SPME fibers that were coated with 100 μm polydimethylsiloxane (Supelco 

Catalog # 57300-U). The operator inserted the SPME fiber, which is housed in a syringe-type 

assembly, into the liquid. After exposing the fiber for a specific amount of time, the operator 

pulled the fiber back into the assembly, and then removed it from the sample. After inserting the 

assembly into the injector port of the CT-1128, the operator exposed the fiber for desorption and 

began the analysis. A SPME mixer heater compartment, which is built into the CT-1128 unit, 

allowed the operator to keep the sample properly mixed and thermally equilibrated. 

Table 3-6. CT-1128 Analytical Methods for Target Contaminants 

Analytes Quantitation 

Ion 

SPME 

Extraction GC Column GC Oven 

Program 

MS 

Scan 

Range 

MS 

Sampling 

Rate 

Total Run 

Time 

benzene 

toluene 

ethylbenzene 

xylenes 

(total) 

78 m/z 

91 m/z 

91 m/z 

91 m/z 

100 μm 007-5MS, 

35°C hold 2 

minutes, ramp 

to 200°C at 

10°C/minute, 

ramp to 300°C 

at 20°C/minute 

35 to 

120 m/z 

5 

 (2.2 

scans/ 

second) 

23.5 

minutes 

2,4-D 

dicrotophos 

162 m/z 

127 m/z 

polydimethylsilo 

xane (Supelco 

57300-U) 

exposed for 20 

minutes at 25°C 

with mixer speed 

= 3 

Siloxane, 30m x 

0.25 mm ID x 

0.25 μm film 

(Quadrex 

Corporation 

007-5MS-30­

Silpheylene 

50°C hold 0.5 

minutes, ramp 

to 300°C at 

15°C/minute, 

hold 5 minutes 

35 to 

250 m/z 

4 (1.75 

scans/ 

second) 

22.2 

minutes 

GB 

GD 

VX 

99 m/z 

126 m/z 

114 m/z 

0.25F) 

50°C hold 0.5 

minutes, ramp 

to 300°C at 

15°C/minute, 

hold 15 minutes 

35 to 

275 m/z 

4 (1.58 

scans/ 

second) 

32.2 

minutes 

Like the choice of SPME fiber, the vendor provided a single GC capillary column (30 m x 0.25 

mm ID x 0.25 μm film, type 007-5MS; Quadrex Corporation, Woodbridge, CT) that was to be 

11 
Table 3-7. Reference Methods for Target Contaminants 

Contaminant Reference Method

VX Battelle Internally Developed Method(a)

GB HMRC-IV-118-05(9)

GD HMRC-IV-118-05(9)

dicrotophos Battelle Internally Developed Method(b)

2,4-D U.S. EPA 515.1(10) 

benzene U.S. EPA 524.2(7) 

toluene U.S. EPA 524.2(7) 

ethylbenzene U.S. EPA 524.2(7) 

xylenes (total) U.S. EPA 524.2(7) 

used for the target contaminants analyzed during the verification test. The operator exposed the 

SPME fiber to the sample for a total absorption time of 20 minutes while the mixer speed was set 

to “3.” After removing the SPME assembly from the sample and inserting it into the injector 

port of the CT-1128, the operator exposed the fiber, and selected the “Start” button in the GC 

control software (which works in tandem with the MS control software). The operator retracted 

and removed the SPME fiber after the end of the 10 minute desorption time. After data 

acquisition, the operator processed the raw data by extracting the appropriate quantitation ion 

from the total ion chromatogram (TIC) and then integrating the corresponding peak using the 

Chemstation software. Using Microsoft Excel, the peak area (response) was plotted against 

expected analyte concentration to generate calibration curves which were used to quantify the 

subsequent sample analyses. Though a single calibration curve was acquired, a midlevel PT 

sample was analyzed at the beginning and end of each day of testing to assess stability of the CT1128 response. 

3.2.2 Non-Laboratory Testing 

The CT-1128 was deployed into a non-laboratory setting to verify its performance in a relatively 

uncontrolled environment. Using the operator’s manual for guidance, the operator set up the CT1128 for analysis in a warehouse located on Battelle’s Columbus campus. The site had electricity 

though temperature and humidity were not as controlled as in a laboratory. For the nonlaboratory analysis, the operator followed the same procedures used in the laboratory and 

analyzed BTEX calibration standards and a water sample that was fortified with BTEX (at 

concentrations unknown to the operator). 

3.3 Reference Methods 

Laboratory reference methods (Table 3-7) were used to determine the accuracy of sample 

preparation and demonstrate the stability of the target contaminants in the PT matrix. The 

reference laboratories were asked to follow the sample preservation/handling and quality control 

(QC) requirements specified in Chapter 4, in addition to any QC requirements specified in each 

reference method. 

(a) VX analysis by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS). 

(b) Dicrotophos analysis by GC-MS. 

HMRC = Hazardous Materials Research Center 

12 
3.3.1 CWA Reference Method 

Samples submitted for GB and GD determination were analyzed by Battelle according to 

procedures outlined in HMRC-IV-118-05. This procedure involves a liquid-liquid extraction of 

the water sample and subsequent analysis of the extract by GC-MS. The samples containing VX 

were analyzed directly in water using an internally developed electrospray ionization liquidchromatography tandem mass spectrometry (LC-MS/MS) method. 

3.3.2 Pesticide Reference Method 

Samples for 2,4-D determination were analyzed according to EPA Method 515.1 in which 

chlorinated acids are extracted and derivatized. The derivatives are then determined by GC using 

an electron capture detector. Samples for dicrotophos determination were analyzed according to 

an internal Battelle method. This procedure involves solid phase extraction followed by GC-MS 

analysis. Battelle performed this method when it was learned that the subcontract laboratory that 

was going to perform EPA Method 8141, as proposed in test/QA plan for this test, (1) no longer 

offered this analysis. 

3.3.3 BTEX Reference Method 

Samples submitted to a subcontract laboratory for BTEX determination were analyzed according 

to EPA 524.2. This “purge and trap” method involves the purging of volatile organic compounds 

with low water solubility and trapping these compounds onto a sorbent tube. The compounds are 

then thermally desorbed and determined by GC-MS. 

13 
Table 4-1. Changes to Test/QA Plan for Verification of Mobile Mass Spectrometers 

Change Further 

Discussion

Proposed PT sample concentrations, as listed in test/QA plan, (1) were changed after 

running preliminary solutions to determine analytical sensitivity. Section 6.8 

Three replicate measurements of the PT samples were not made for two analytes: 2,4-D 

and dicrotophos. Section 3.1.1 

Accuracy was determined using the theoretical concentration of target analyte instead of

the concentration of the target analyte determined by the reference measurement. Section 4.1.1 

Research trailer was not available during time of field testing and one PT sample was 

analyzed (instead of triplicate analysis of a raw water sample). Section 6.7 

The reference methods for VX and dicrotophos were changed. Section 3.3 

Reference samples were submitted for analysis to demonstrate that the PT samples can

be prepared accurately. In particular, BTEX and 2,4-D reference methods were most Section 4.1.1 

problematic. 

Only PT samples were analyzed for VX. Section 6.1 

Relative percent difference (RPD) was used to measure instrument stability instead of

percent recovery (R) of PT samples analyzed on each day of testing. Section 5.5 

Chapter 4

Quality Assurance Quality Control 

QA/QC procedures were performed in accordance with the quality management plan (QMP) for 

the AMS Center (11) and the test/QA plan for this verification test (1) except as noted in Table 4-1. 

14 
Table 4-2. Summary of Reference Measurement Percent Recovery (R) 

R of Reference Contaminant Measurements

VX 124% 

GB 80%

GD 87%

dicrotophos 99%

2,4-D 64% 

benzene 86%

toluene 52%

ethylbenzene 46% 

xylenes (total) 52% 

A summary of the recovery values (R) for the reference measurements is presented in Table 4-2 

(a definition of R is included in Section 5.1). R values for benzene, dicrotophos, and the CWAs 

were all 80% or greater. Sample degradation was suspected as the cause for lower recoveries 

observed with the other chemicals. 

Reference analyses for BTEX and 2,4-D did not meet acceptance criteria for all samples. The 

EPA-specified holding time for laboratories using EPA method 524.2 for BTEX analysis is 14 

days. Several of the samples could not be confirmed to have been analyzed within this specified 

holding time due to discrepancies in the chain of custodies. Also, a number of results were 

received with low surrogate recoveries. In addition, as shown in Table 4-2, sample recovery was 

near 50% for all BTEX analytes except benzene which was 86%. Of 11 samples submitted for 

2,4-D analysis, 7 samples were analyzed after the recommended 14 day holding time per EPA 

method 515.1. 

Based on these deficiencies in the reference analyses and since test samples were prepared daily, 

these reference results were not used to determine accuracy of the CT-1128 GC-MS analytical 

measurement, but rather to confirm that sample preparation was being performed properly. 

Since sample preparation procedures were standardized and no systematic errors were observed 

in the reference measurements, the results provide confidence in the sample preparation. There 

is no impact on the data because it is a common practice to use the theoretical fortified value for 

comparison. 

4.1 Audits 

A performance evaluation audit, a technical systems audit, and an audit of data quality were 

performed for this verification test. 

4.1.1 Performance Evaluation Audit 

For all contaminants, “blind” samples were submitted to analysts performing the reference 

measurements. Since the methods are specific to the contaminant, only the concentration of 

target contaminants was not disclosed when submitting samples for reference measurements. 

15 
These performance evaluation (PE) samples were used to assess the accuracy of the reference 

measurements and were prepared in accordance with the stated detection limits of the reference 

laboratories. At least one PE sample was submitted per reference method prior to the start of the 

verification test and once during the verification test. PE samples that were not within ± 20% of 

the expected result were repeated. 

4.1.2 Technical Systems Audit 

The Battelle Quality Manager conducted a technical systems audit (TSA) to ensure that the 

verification test was performed in accordance with the test/QA plan (1) and the AMS Center 

QMP. (11) As part of the audit, the Battelle Quality Manager reviewed the reference methods, 

compared actual test procedures to those specified in the test/QA plan, and reviewed data 

acquisition and handling procedures. Observations and findings from this audit were documented 

and submitted to the Battelle Verification Test Coordinator for response. No findings were 

documented that required any significant action. The records concerning the TSA are 

permanently stored with the Battelle Quality Manager. 

4.1.3 Audit of Data Quality 

At least 10% of the data acquired during the verification test was audited. Battelle’s Quality 

Manager traced the data from the initial acquisition, through reduction and statistical analysis, to 

final reporting, to ensure the integrity of the reported results. All calculations performed on the 

data undergoing the audit were checked. 

4.2 QA/QC Reporting 

Each internal assessment and audit was documented in accordance with Sections 3.3.4 and 3.3.5 

of the QMP for the ETV AMS Center. (11) Once the assessment report was prepared, the Battelle 

Verification Test Coordinator ensured that a response was provided for each adverse finding or 

potential problem and implemented any necessary follow-up corrective action. The Battelle 

Quality Manager ensured that follow-up corrective action was taken. The results of the TSA 

were sent to EPA. 

4.3 Data Review 

Records generated in the verification test were reviewed before these records were used to 

calculate, evaluate, or report verification results. Table 4-3 summarizes the types of data 

recorded. The review was performed by a technical staff member involved in the verification 

test, but not the staff member who originally generated the record. The person performing the 

review added his/her initials and the date to a hard copy of the record being reviewed. 

16 
Table 4-3. Summary of Data Recording Process 

Data to be Recorded 

Responsible 

Party Where Recorded 

How Often 

Recorded Disposition of Data 

Dates, times, and 

details of test events, 

mass spectrometer 

maintenance, down 

time, etc. 

Battelle ETV laboratory 

record books or 

data recording 

forms 

Start/end of test 

procedure, and at 

each change of a test 

parameter or change 

of instrument status 

Used to organize/check test 

results; manually incorporated in 

data spreadsheets as necessary 

Mass spectrometer 

calibration 

information 

Battelle ETV laboratory 

record books or 

electronically 

At instrument 

calibration or 

recalibration 

Incorporated in verification report 

as necessary 

Mass spectrometer 

readings 

Battelle Recorded 

electronically by 

each instrument 

and then 

downloaded daily 

For each sample Converted to spreadsheet for 

statistical analysis and 

comparisons 

Reference method 

sample preparation 

Battelle Laboratory record 

books 

Throughout sample 

preparation 

Used to demonstrate validity of 

samples submitted for reference 

measurements 

Reference method 

procedures, 

calibrations, QA, etc. 

Battelle or 

subcontract 

laboratory 

Laboratory record 

books, or data 

recording forms 

Throughout sampling 

and analysis 

processes 

Retained as documentation of 

reference method performance 

Reference method 

analysis results 

Battelle or 

subcontract 

laboratory 

Electronically 

from reference 

analytical method 

Every sample 

analysis 

Converted to spreadsheets for 

calculations 

17 
Chapter 5

Statistical Methods and Reported Parameters

The statistical methods presented in this chapter were used to verify the performance parameters 

listed in Chapter 3. 

5.1 Accuracy 

Determination of accuracy of the PT samples was based on the concentration of the prepared 

standards. A minimum of three concentrations of PT samples was used to establish the 

calibration curve. All subsequent analyses of the PT samples were used to determine the 

accuracy of the CT-1128 relative to the prepared concentrations. Ideally, independent reference 

measurements would be used to confirm the accuracy of the technology. However, as discussed 

in Chapter 4, the reference laboratory measurements (particularly in the case of BTEX and 2,4­

D) were of questionable quality due to analytical holding times that were exceeded and 

inadequate QC results. Accuracy of the CT-1128 was therefore determined for all target 

contaminants using the prepared concentrations rather than the reference laboratory 

concentrations. The subsequent analyses of the PT samples for determination of accuracy 

included two types: 1) analysis of an additional two replicate sets of PT samples (except for 2,4­

D and dicrotophos where, as described in Section 3.1.1, the calibration curve PT samples were 

not repeated) and 2) daily verifications of the mid-level PT samples. The accuracy of the CT1128 was assessed as recovery (R), using Equation 1:

R = (Yi ÷ Xi )×100 (1) 

where Yi is the concentration of target contaminant i as measured by the CT-1128 and Xi is the 

prepared concentration of the contaminant i. R values are presented for PT samples. The ideal R 

value is 100%. The mean, median, maximum, and minimum R values are presented, as well as 

the standard deviation of the R values. 

5.2 Precision 

When possible, the relative standard deviation (RSD) of three replicate measurements of the PT 

samples across three or four concentrations was determined to assess the precision of the CT18 
1128 measurements. Precision was also evaluated on replicate measurements of mid-level PT 

samples that were used as daily calibration verifications. Lastly, the precision of replicate matrixfortified samples was calculated. Regardless of the type of sample analyzed, the precision was 

defined as the RSD of replicate measurements, using Equation 2:

RSD = (SD ÷Yi) ×100 (2) 

where Yi is the average concentration of target contaminant i as measured by the CT-1128, and 

SD, the standard deviation of the results. Ideal RSD values are near 0%. 

5.3 Linearity 

Linearity was determined by performing a linear regression analysis of the instrument response 

for one set of the PT samples versus the theoretical target contaminant concentrations across a 

minimum of three concentrations. The linear regression analysis used the target contaminant 

concentration as the independent variable and the response (integrated peak area for the 

contaminant of interest) from the CT-1128 as the dependent variable. Linearity was expressed in 

terms of slope, intercept, and coefficient of determination (r2

), in addition to presenting a plot of 

the data. The ideal value for r2

 is 1. 

5.4 Sensitivity 

Sensitivity was assessed by the ability of the CT-1128 to measure the target contaminant at or 

below the concentration of interest. This evaluation did not focus on determining instrumental 

detection limits since the purpose was to ascertain whether the CT-1128 was sensitive enough to 

measure the target contaminants at the concentrations of interest in the various water matrices. 

Serial ten-fold dilutions of the lowest concentration PT sample were performed until no change 

in instrument response for the target contaminant was observed. It was also noted whether the 

instrument response changed accordingly (e.g., ten-fold decrease for each ten-fold dilution). 

5.5 Instrument Stability 

Instrument stability (S) was determined by analyzing a PT sample at the beginning and end of 

the analytical sequence (usually over the course of a day) to assess the degree of calibration 

stability. The result of the PT sample at the end of the sequence was compared to that of the PT 

sample analyzed at the start of the analytical sequence using Equation 3:

RPD = [ (Yi2 −Yi1) ÷ average (Yi1,Yi 2)]×100 (3) 

where Yi2 and Yi1 are the results for the last and first PT sample, respectively, for target 

contaminant i. The ideal value for relative percent difference (RPD) is 0%. 

19 
5.6 Potential Matrix and Interference Effects 

Potential matrix and interference effects were assessed by comparing the response of the various 

test matrices fortified with the target contaminants to the average response of the PT samples 

analyzed on the day of testing. In the absence of instrument drift and target contaminant 

degradation, it was assumed that a matrix or interferent effect was responsible for any change in 

performance for the mid-level PT sample. The matrix effects were calculated using the percent 

recovery calculation. R values between 70% and 130% indicated that a matrix effect was not 

observed, while R values outside of that range were considered to indicate a matrix effect. 

5.7 Field Portability 

For this verification test, field portability was defined as the ability for a user to operate the CT1128 in a non-laboratory environment for sample analysis. Observations related to field 

portability were observed and reported. These considerations included weight and dimensions of 

unit, impact on user mobility, start-up time, and power requirements. 

5.8 Operational Factors 

Operational factors such as maintenance needs, data output, consumables used, ease of use, 

repair requirements, and sample throughput were evaluated based on observations recorded by 

Battelle staff. A separate laboratory record book was maintained for the CT-1128 and was used 

to enter daily observations on these factors. Examples of information to be recorded in the record 

book include the status of diagnostic indicators for the CT-1128, use or replacement of any 

consumables, the effort or cost associated with maintenance or repair, vendor effort (e.g., time on 

site) for repair or maintenance, the duration and causes of any instrument down time or data 

acquisition failure, and operator observations about ease of use of the CT-1128. These 

observations were summarized to aid in describing CT-1128 performance. 

The time required for each sample from the start of sample preparation to reporting of results 

defined sample time. The number of samples that could be analyzed per unit time defined sample 

throughput. The sample throughput was noted for laboratory and field portions of testing. 

20 
Chapter 6

Test Results 

6.1 Accuracy 

Accuracy (Tables 6-1a-g), expressed as percent recovery (R), was determined using the equation 

given in Section 5.1. This calculation was only performed on PT samples since these samples 

represent the matrix free of any potential interference (ASTM Type II DI water). In all cases, 

with the exception of toluene, the integrated peak areas of the first replicate set of three or four 

PT sample concentrations including the blank when possible (all cases except for CWAs where 

no blanks were analyzed) were used to generate a linearly regressed calibration curve on which 

quantitation was based. For toluene, the third replicate set was used to generate the curve due to 

non-linear response of the lower standards on the first two replicates. In addition to presenting 

the mean R for each PT level (when more than one PT level was tested) the median, maximum, 

and minimum R are reported along with the standard deviation of the R values in Tables 6-1a-g. 

For observations of less than three, standard deviation of R was not determined (as indicated by 

“nd”). Overall statistics that combine all R values across all concentrations are also presented to 

summarize the accuracy results for each target analyte. Note that the number of observations for 

the mid-level PT samples (i.e., PT 2 or PT 3) is considerably higher than that of the other 

concentration levels due to the periodic calibration checks that were performed daily. 

21 
Table 6-1a. Accuracy (Percent Recovery) Results – Benzene 

Benzene PT Level Observations Mean Median Maximum Minimum SD 

PT 1 (0.01 mg/L) 4 168% 126% 305% 115% 91% 

PT 2 (0.10 mg/L) 3 116% 115% 124% 109% 7% 

PT 3 (1.00 mg/L) 25 189% 135% 399% 81% 111% 

PT 4 (10.00 mg/L) 3 94% 91% 103% 87% 8% 

benzene ALL 35 172% 125% 399% 81% 103% 

For benzene, accuracy is considerably higher than ideal (100%) at 172% overall mean R. This is 

primarily due to a change in response for benzene observed several days into testing after 

establishing the calibration curve. It could not be determined whether the change was due to the 

SPME extraction of benzene or the instrumental response for benzene. The response for a 

particular analyte may change over the course of several days and may be due to a number of 

factors including the extraction technique or environmental conditions; in such a case, it is 

usually left to the operator’s discretion whether to reacquire a calibration curve. It is important to 

note that this procedure was followed throughout testing (i.e., one calibration curve for each 

analyte was used to quantify results from subsequent testing). The high degree of variability in 

the benzene response throughout testing using the single curve is reflected by the SD of the R. 

Table 6-1b. Accuracy (Percent Recovery) Results – Toluene 

Toluene PT Level Observations Mean Median Maximum Minimum SD 

PT 1 (0.001 mg/L) 4 299% 251% 533% 160% 162% 

PT 2 (0.01 mg/L) 3 261% 94% 599% 91% 292% 

PT 3 (0.10 mg/L) 25 508% 611% 770% 67% 237% 

PT 4 (1.00 mg/L) 3 243% 126% 489% 114% 213% 

toluene ALL 35 440% 489% 770% 67% 248% 

Toluene was the least accurate of the BTEX compounds tested, exhibiting significant overrecoveries with an overall mean R of 440%. The third set of replicates was used to generate the 

calibration curve since it was the most linear of the replicate sets of PT samples. The high degree 

of variability in the toluene response is reflected by the SD of the R. 

Table 6-1c. Accuracy (Percent Recovery) Results – Ethylbenzene 

Ethylbenzene PT Level Observations Mean Median Maximum Minimum SD 

PT 1 (0.001 mg/L) 4 102% 94% 140% 82% 26% 

PT 2 (0.01 mg/L) 3 99% 89% 130% 79% 27% 

PT 3 (0.10 mg/L) 25 110% 121% 143% 66% 27% 

PT 4 (1.00 mg/L)(a) 3 58% 55% 65% 54% 6% 

ethylbenzene ALL 35 104% 102% 143% 54% 29% 

(a) PT 4 not used in calibration curve due to suspected detector saturation 

The CT-1128 exhibited accuracy for ethylbenzene that was usually in the range of 70-130%, 

with a mean of 104%, and relatively small standard deviations of the R values. Ethylbenzene 

demonstrated reduced accuracy at the PT 4 concentration level (1.00 mg/L), which may have 

22 
been due to detector saturation. Therefore, PT 4 was not included in the calibration curve for this 

analyte. 

Table 6-1d. Accuracy (Percent Recovery) Results – Xylenes (Total) 

Xylenes (total) PT Level Observations Mean Median Maximum Minimum SD 

PT 1 (0.001 mg/L) 4 124% 117% 158% 105% 23% 

PT 2 (0.01 mg/L) 3 89% 80% 113% 73% 21% 

PT 3 (0.10 mg/L) 25 104% 113% 136% 62% 24% 

PT 4 (1.00 mg/L) 3 77% 74% 84% 73% 6% 

xylenes ALL 35 103% 109% 158% 62% 25% 

To produce the total xylenes result, the operator added the response for both m- and p-xylene 

(which were not resolved from each other) to that of o-xylene to produce a total response. 

Though the PT 4 sample was excluded from the calibration curve for xylenes as it was in 

ethylbenzene, accuracy was not affected to the same extent. Total xylenes R was close to ideal, 

with a mean R value of 103% and a relatively low SD. 

Table 6-1e. Accuracy (Percent Recovery) Results – 2,4-D and Dicrotophos 

2,4-D PT Level Observations Mean Median Maximum Minimum SD 

PT 3 (50.0 mg/L) 8 62% 66% 79% 29% 16% 

Dicrotophos PT Level Observations Mean Median Maximum Minimum SD 

PT 3 (500.0 mg/L) 8 143% 104% 520% 7% 160% 

Since only one replicate of each PT sample was analyzed for 2,4-D and dicrotophos, accuracy 

was determined using the PT 3 check samples that were analyzed each day of testing. Accuracy 

for 2,4-D was less than ideal as the method was not sensitive for this contaminant. For 

dicrotophos, the PT 4 sample was excluded from the calibration curve as it did not give a linear 

response with respect to the other PT samples. The dicrotophos response showed high variability 

as reflected in the SD of the R. 

Table 6-1f. Accuracy (Percent Recovery) Results – GB and GD 

GB PT Level Observations Mean Median Maximum Minimum SD 

PT 1 (0.5 mg/L) 5 120% 130% 185% 51% 53% 

PT 2 (1.0 mg/L) 18 106% 119% 185% 35% 51% 

PT 3 (10.0 mg/L) 4 101% 114% 140% 36% 46% 

GB ALL 27 108% 127% 185% 35% 49% 

GD PT Level Observations Mean Median Maximum Minimum SD 

PT 1 (0.5 mg/L) 5 74% 70% 126% 47% 32% 

PT 2 (1.0 mg/L) 18 72% 70% 148% 15% 33% 

PT 3 (10.0 mg/L) 4 92% 95% 115% 65% 21% 

GD ALL 27 75% 74% 148% 15% 31% 

For GB, the mean accuracy (R) was near ideal at 108%. For GD, the mean R was 75%, though 

the variability was less than that of the GB response (as reflected in SD of R). The spiking 

23 
solution used to fortify the water samples with these two CWAs contains several other chemicals 

which affected the library matching for GB (resulting in a lower quality match for this analyte). 

As shown in Figures 6-1a and 6-1b, the operator was able to use the background subtracting 

feature of Chemstation to improve the quality of the library match (and thus, the confidence in 

the identification) of GB in the sample from a quality of 50 before the background subtraction to 

a quality of 83 after the background subtraction. 

Figure 6-1a. Library Match for GB without Background Subtraction 

24 
Figure 6-1b. Library Match for GB with Background Subtraction 

25 
Table 6-1g. Accuracy (Percent Recovery) Results – VX 

VX PT Level Observations Mean Median Maximum Minimum SD 

PT 1 (10.0 mg/L) 2 113% 113% 126% 100% nd 

PT 2 (15.0 mg/L) 2 104% 104% 119% 89% nd 

PT 3 (30.0 mg/L) 2 111% 111% 111% 111% nd 

VX ALL 6 109% 111% 126% 89% 13% 

nd = SD of R not calculated for observations less than three 

Due to the lack of sensitivity for the originally proposed testing levels for VX, data were limited 

to three sets of replicates, including the set of replicates from which data were plotted to generate 

the calibration curves that were used to quantify the subsequently acquired data. Since there were 

only two replicates, SD was not calculated for each PT sample level (though SD is provided for 

all PT sample levels combined). Mean recovery for VX was 109%. 

6.2 Precision 

Precision (Table 6-2), expressed as RSD, was calculated for the three replicate measurements of 

the PT samples and matrix-fortified samples (except for 2,4-D and dicrotophos, in which cases 

only matrix-fortified samples were used for the calculation, and VX, in which case no matrix 

samples were analyzed) by the method listed in Section 5.2. RSD values ranged from 1% to 

100% with several trends observed. When compared to benzene and xylenes, where only one 

sample type showed a RSD greater than 20%, toluene and ethylbenzene, 2,4-D, dicrotophos, GB, 

and GD had multiple samples types with a RSD greater than 20%. This variable response may be 

due to either the SPME or the CT-1128 (or contributions from both sources). Additionally, DW3, 

a groundwater sample, exhibited a RSD greater than 20% for six of the eight analytes tested. 

Table 6-2. Summary of RSD of the Various Sample Types(a) 

Sample Type Benzene Toluene Ethylbenzene Xylenes 2,4-D Dicrotophos GB GD VX 

PT 1 4% 198% 12% 6% NA NA 26% 26% 22% 

PT 2 4% 1% 11% 13% NA NA 48% 32% 15% 

PT 3 5% 61% 6% 8% NA NA 48% 24% 7% 

PT 4 7% 12% 1% 2% NA NA NA NA NA 

DW1 3% 6% 36% 7% 36% 30% 10% 4% NA 

DW2 7% 7% 44% 14% 17% 19% 4% 2% NA 

DW3 50% 66% 52% 3% 25% 68% 23% 18% NA 

DW4 13% 14% 3% 14% 15% 77% 20% 13% NA 

Weakly Buffered 

Water (442-30) 9% 100% 11% 13% 9% 24% 9% 1% NA 

Strongly Buffered 

Water (442-3000) 3% 3% 4% 5% 32% 58% 27% 14% NA 

THMs Spiked 

Water (ASTM 

Type II Water) 

5% 3% 0% 30% 16% 17% 21% 7% NA 

NA = Not applicable. 

(a) Entries in bold italics indicate RSD > 20%. 

26 
6.3 Linearity 

For all target contaminants, a minimum of three PT samples were used to generate a calibration 

curve as described in Section 5.3. The curves (Figures 6-2a-i) were constructed from the same 

set of replicates if multiple replicates were analyzed (e.g., the first set of PT sample replicates 

was used to generate the calibration curve for benzene calibration). When a blank sample was 

analyzed as part of the calibration curve, the blank response was included in the construction of 

the corresponding calibration curve. It should be noted that not every concentration level of PT 

samples was used to construct the curves. For some (ethylbenzene, xylenes, and dicrotophos), 

the highest PT sample level was removed to yield better calibration curves. Table 6-3 

summarizes the calibration curve results. Calibration for seven of the nine analytes yielded 

curves with coefficient of determination, r2

, of 0.999 or greater. The notable exceptions are those 

analytes for which the provided method lacked sensitivity, 2,4-D and VX (r2

 of 0.921 and 0.959, 

respectively), though all of the r2

 values were greater than 0.920. The number of days for which 

the calibration curve was used to quantitate data is also indicated in Table 6-3. 

Table 6-3. Summary of Calibration Curve Data 

Contaminant Number of 

Points in Curve 

Range 

(mg/L) r

2 Number of Days 

Curve was Used 

benzene 5 0 to 10 1.000 8 

toluene 5 0 to 1 1.000 8 

ethylbenzene 4 0 to 0.1 (1 not linear) 1.000 8 

xylenes 4 0 to 0.1 (1 not linear) 1.000 8 

2,4-D 5 0 to 100 0.921 5 

dicrotophos 4 0 to 500 (1000 not 

linear) 0.999 5 

GB 3 0.5 to 10 1.000 9 

GD 3 0.5 to 10 1.000 9 

VX 3 10 to 30 0.959 1 

27 
CT-1128 Response (Peak Area) 

n = 5 CT-1128 9-13 Calibration Benzene SPME 

r

2

 = 1.000 

7000000 

6000000 

y = 578244x - 1098 

0 2 4 6 8 10 

Expected Concentration (mg/L) 

5000000 

4000000 

3000000 

2000000 

1000000 

0 

Figure 6-2a. Calibration Curve for Benzene 

CT-1128 9-13 Calibration Toluene SPME n = 5 

r

2

 = 1.000 

1600000 

CT-1128 Response (Peak Area) 1400000 

1200000 

1000000 

800000 

600000 

400000 

200000 

0 

y = 1471470x + 3319 

0 0.2 0.4 0.6 0.8 1 1.2 

Expected Concentration (mg/L) 

Figure 6-2b. Calibration Curve for Toluene 

28 

12 
CT-1128 9-13 Calibration Ethylbenzene SPME n = 4

r

2

 = 1.000

2500000

CT-1128 Response (Peak Area) 2000000

1500000

1000000

500000

0

y = 22080249x - 1631 

0 0.02 0.04 0.06 0.08 0.1 0.12 

Expected Concentration (mg/L) 

Figure 6-2c. Calibration Curve for Ethylbenzene 

CT-1128 9-13 Calibration Xylenes SPME n = 4

r

2

 = 1.000

y = 22238885x - 8173 

-500000 

0 

500000 

1000000 

1500000 

2000000 

2500000 

0 0.02 0.04 0.06 0.08 0.1 0.12 

CT-1128 Response (Peak Area) 

Expected Concentration (mg/L) 

Figure 6-2d. Calibration Curve for Xylenes (Total) 

29 
CT-1128 9-29 Calibration Dicrotophos SPME n = 4 

r

2

 = 0.999 

1000000 

eak Area) 

900000 

800000 

P

y = 1799x + 4308 (

700000 

se n

600000 

8 Respo

500000 

400000 

CT-112

300000 

200000 

100000 

0 

0 100 200 300 400 500 600 

Expected Concentration (mg/L) 

Figure 6-2f. Calibration Curve for Dicrotophos 

CT-1128 9-29 Calibration 2,4-D SPME n = 5 

r

2

 = 0.921 

y = 6552x - 27045 

-100000 

0 

100000 

200000 

300000 

400000 

500000 

600000 

700000 

800000 

CT-1128 Response (Peak Area) 

0 20 40 60 80 100 120

Expected Concentration (mg/L) 

Figure 6-2e. Calibration Curve for 2,4-D 

30 
CT-1128 11-01 Calibration GB SPME n = 3 

r

2

 = 1.000 

ea) 100000 

r

90000 

eak A

80000 y = 8710x - 1015 

P

70000 

se (

60000 

n

50000 

espo

40000 

128 R

30000 

20000 

1-

10000 

TC

0 

024 6 810 12

Expected Concentration (mg/L) 

Figure 6-2g. Calibration Curve for GB 

CT-1128 11-01 Calibration GD SPME n = 3 

r

2

 = 1.000 

ea) 800000 

r

700000 

ak A

y = 69391x + 12827 

e

600000 

P(

500000 

se pon

400000 

se

300000 

 R

200000 

1128-

100000 

TC

0 

0 24 6 810 12

Expected Concentration (mg/L) 

Figure 6-2h. Calibration Curve for GD 

31 
CT-1128 11-01 Calibration VX SPME n = 3 

r

2

 = 0.959 

700000 

k ea

600000 

P (

y = 26300x - 165810 

es

500000 

no

) 

p

a

400000 

se

Are

300000 

8 R

200000 

121-T

100000 

C

0 

0 5 10 15 20 25 30 35 

Expected Concentration (mg/L) 

Figure 6-2i. Calibration Curve for VX 

6.4 Sensitivity 

Sensitivity, as defined in Section 5.4, is the ability to determine the target contaminant at the 

concentration of interest in the various water matrices. Results of the sensitivity evaluation are 

shown in Table 6-4. For VX and 2,4-D, the concentrations of interest were not achieved due to 

lack of sensitivity using the provided method. With the exception of benzene, all other 

contaminants were spiked lower than the concentration of interest in the various matrices (see 

Table 3-3). For benzene, determining whether the CT-1128 was sensitive enough to detect the 

concentration of interest was determined using dilutions of the lowest PT sample. Serial ten-fold 

dilutions of PT 1 were performed for each contaminant, and the dilutions were made and tested 

until the instrument response did not change by the approximate corresponding dilution factor. 

For many of the target contaminants, the response at these levels, while low, may be sufficient 

for a qualitative result or identification. 

Table 6-4. Sensitivity of CT-1128 

Contaminant 

Concentration 

of Interest 

(mg/L)(a) 

Sufficient Sensitivity 

to Detect Conc. of 

Interest 

benzene 0.005 Yes 

toluene 1 Yes 

ethylbenzene 0.7 Yes 

xylenes 10 Yes 

2,4-D 0.07 No 

dicrotophos 1400 Yes 

GB 20 Yes 

GD 1.4 Yes 

VX 2.1 No 

(a) See Table 3-1 for Target Contaminants and Concentrations of Interest. 

32 
6.5 Instrument Stability 

Stability (Table 6-5), determined by the method described in Section 5.5, was based on the first 

and last PT sample of a testing day, expressed as an RPD of the two. The ideal RPD is zero with 

those results greater than 20% flagged (those results listed in bold italics). In addition to 

presenting the mean percent recovery for each PT level, median, maximum, minimum, and 

standard deviation of RPD were reported. Though the verification test involved acquiring a 

single calibration which was used for the duration of testing (the number of days over which 

stability was tested is indicated in Table 6-5), it is recommended that an operator acquire a new 

calibration curve when the response has changed. This frequency will depend on the operator’s 

need for accuracy and precision. Alternatively, the operator may use the average response of 

standards analyzed throughout an analytical run to normalize the sample results for instrumental 

drift. This approach was used by the operator in determining potential matrix effects and 

interferents. For example: PT 3 samples for benzene, expected to be 1.0 mg/L gave 3.8, 3.9, and 

3.7 mg/L for an average response of 3.8 mg/L throughout the testing day when THMs fortified 

water samples were analyzed. When determining the R of benzene in the matrix, the operator 

normalized the THMs-matrix response, which was 3.9, 3.9, and 4.2 for an average response of 

4.01 mg/L to the PT 3 response, giving average R as 106%. 

Table 6-5. Results of Stability Testing for CT-1128 

Contaminant PT Level 

(mg/L) 

Number of 

Days 

Stability (RPD)(a) 

Mean Median Maximum Minimum SD 

benzene 1.00 8 27% 10% 100% 1% 39% 

toluene 0.10 8 52% 14% 133% 3% 61% 

ethylbenzene 0.10 8 9% 10% 17% 0% 5% 

xylenes 0.10 8 12% 10% 33% 1% 10% 

2,4-D 50.0 4 35% 23% 83% 10% 33% 

dicrotophos 500 4 92% 81% 195% 11% 80% 

GB 1.00 7 48% 50% 83% 7% 31% 

GD 1.00 7 27% 33% 63% 3% 22% 

(a) The ideal RPD is zero with those results greater than 20% flagged (those results listed in bold italics) 

The average RPD ranged from that for ethylbenzene (average RPD of 9% with a SD of 5%) to 

that for dicrotophos (average RPD of 92% with a SD of 80%). Only two analytes, ethylbenzene 

and xylenes (average RPD of 9% and 12%, respectively) had average RPD less than 20%, while 

results for toluene and dicrotophos were much greater than 20% (average RPD of 52% and 92%, 

respectively). 

6.6 Potential Matrix and Interference Effects 

The ability of the CT-1128 to detect the target contaminants was challenged by analysis of 

fortified samples in different matrices. The results are shown in Table 6-6. To determine 

percent recovery (R) of the fortified samples, the average response of the PT samples throughout 

the day of testing was used. A matrix effect was defined as recoveries outside of the range of 

70% to 130% R value. A trend was observed with the strongly buffered water matrix (442-3000) 

which gave R outside of that range, indicating that a matrix effect may be present. This result 

33 
may be due to an enhancement of the SPME efficiency, which has been observed with the 

extraction of analytes in high salt matrices. Results for 2,4-D may be due to sensitivity issues. 

For dicrotophos, all but two of the sample types exhibited matrix effects which may also be due 

to a less than optimal method for the contaminant. DW3 also showed matrix effects for five of 

the eight contaminants tested which may be due to the fact that it is the sole groundwater sample 

of the four regional DWs. Potential matrix and interference effects were not tested for VX due to 

the lack of sensitivity for this contaminant using the provided method. 

Table 6-6. Results of Potential Matrix and Interference Effects 

Contaminant 

Matrix Effects Observed(a) 

DW1 DW2 DW3 DW4 

Weakly 

Buffer ed 

Water 

(442-30) 

Strongly 

Buffered 

Water 

(442-3000) 

THMs 

Spiked 

Water 

benzene 120% 82% 88% 108% 58% 218% 106% 

toluene 107% 193% 180% 95% 39% 158% 99% 

ethylbenzene 96% 102% 88% 109% 94% 139% 101% 

xylenes 102% 129% 115% 99% 99% 135% 87% 

2,4-D 17% 30% 22% 13% 90% 16% 110% 

dicrotophos 103% 142% 349% 143% 162% 236% 121% 

GB 80% 123% 63% 79% 91% 38% 140% 

GD 159% 92% 61% 133% 90% 66% 134% 

VX ND ND ND ND ND ND ND 

(a) bold italic font indicates values outside 70-130% range of average response of daily PT samples 

ND = no data; VX matrix testing was not performed due to lack of sensitivity for this contaminant using the vendor 

provided method 

6.7 Field Portability 

The CT-1128 was removed from the laboratory to be installed and operated within a warehouse 

facility. To begin the move, the CT-1128 was shut down after a day of laboratory analysis. The 

heating zones were cooled and the turbo pumps were subsequently allowed to spin down. After 

venting the instrument, the instrument was packed into the hard transport case for mobilization 

into the field. This aspect of transportability was straightforward. The CT-1128 unit weighs 

approximately 70 pounds so it is possible to load the unit into a specially designed hard case 

using two people. The hard case held the CT-1128 securely and protected the instrument during 

mobilization. The packed CT-1128 (which, with its hard case, weighed approximately 225 

pounds (102 kg) and measured 36” (91.4 cm) x 36” (91.4 cm) x 39” (99.1 cm)) was loaded onto 

the back of a pickup truck. 

34 
Battelle has a warehouse facility in Columbus, Ohio that is located along the banks of the 

Olentangy River. This location was selected for its proximity to the river, as a possible scenario 

could involve analyzing grab water samples from the river using the CT-1128. To shield the 

instrument from the rain, the truck was moved inside the warehouse (Figure 6-3). The instrument 

was powered and supplied with UHP helium from a gas tank (alternatively, the CT-1128’s 

internal metal hydride storage bottle may be charged to supply hydrogen as the carrier gas but 

this was not tested during this verification test). After establishing the gas flow, the source and 

quad temperatures were heated. The system was packed and transported at 8:00 A.M. and by 

9:30 A.M., the CT-1128 was installed and under vacuum, though it was necessary to wait for the 

instrument to reach thermal equilibrium prior to performing the autotune procedure. Though a 

dialog box in the MSD Chemstation software tells the operator to wait for two hours, the vendor 

claims that the instrument may be operated to obtain data well before this time (this was not 

verified as part of the test). At approximately 11:30 A.M., an autotune was performed, followed 

by an air and water check. It was at this time that the results of the check indicated an air leak. 

After spending a significant amount of time leak checking the system, a stress fracture in the 

helium gas line was discovered and replaced. After replacing the gas line, several air and water 

checks were performed and showed the N2 and O2 peaks to be gradually decreasing. After 

obtaining a satisfactory air and water check (abundance of H2O, N2, and O2 should all be less 

than 10% of the internal calibrant PFTBA), the instrument was left on standby (as the workday 

had come to an end). This type of effort highlights the advantage of operating the CT-1128 in a 

mobile laboratory environment (e.g., van with source of electrical power) so that downtime 

associated with re-establishing vacuum and tuning, which can be several hours, may be 

minimized dramatically, allowing the operator to analyze field samples sooner. 

On the following day, the 

operator tuned the MS and 

performed a four-point 

calibration for BTEX 

analytes. A separate 

individual prepared the 

standards and provided a 

water sample fortified with 

BTEX at concentrations 

unknown to the operator. 

The operator analyzed the 

sample and determined 

concentrations of the 

BTEX analytes based on 

the acquired calibration 

curve. The results are 

presented in Table 6-7. 

The recoveries were 

comparable to what was 

observed in the laboratory 

with recoveries for 

benzene, ethylbenzene, and 

xylenes at 108%, 135%, and 121% respectively. However, the accuracy for toluene was low, 

Figure 6-3. Use and Installation of CT-1128 Outside of the 

Laboratory 

35 
which is opposite to the behavior observed in the laboratory testing (during which a mean 

recovery of 440% was observed – see Table 6-1b). This may be due to a non-optimal method for 

this contaminant. Overall, in terms of analytical performance, no major differences were 

observed due to field deployment. 

Table 6-7. Field Portability Results 

Contaminant PT Conc. Level (mg/L) Linearity Conc. of Blind 

Sample (mg/L) 

Accuracy (R of 

Blind Sample) PT 1 PT 2 PT 3 PT 4 r

2 

benzene 0.01 0.10 1.00 10.0 1.000 1.00 108 

toluene 0.001 0.01 0.10 1.00 0.996 0.10 23 

ethylbenzene 0.001 0.01 0.10 1.00 0.998 0.10 135 

xylenes 0.001 0.01 0.10 1.00 1.000 0.10 121 

Since the CT-1128 requires approximately two hours to equilibrate once electrical power and gas 

have been supplied, it is recommended that the instrument be kept on standby as long as possible 

when time for analyzing field samples is a critical factor. Mobilization into the field is 

straightforward and is due in large part to the “button up” design of the CT-1128 and its 

transport-ready case. When the on-board metal hydride canister is used to supply carrier gas, the 

CT-1128 requires only a source of electrical power for several hours of field deployment. The 

advantage of on-site analysis of chemicals makes the CT-1128 a powerful tool for the 

identification and analysis of chemicals that have been traditionally analyzed by a fixedlaboratory GC-MS system. 

6.8 Operational Factors 

In general, GC-MS systems are sophisticated analytical instruments that require proper method 

development and an experienced operator to yield optimal results. The verification test was 

conducted using experienced GC-MS operators running the analytical methods provided by the 

vendor. It is important to note that these methods were not explicitly confirmed by the vendor 

using the levels proposed prior to the verification test. For all analytes, the PT sample starting 

concentrations had to be determined experimentally in order to determine appropriate levels (as 

opposed to the levels listed in test/QA plan for this test (1)). In the case of CWAs, this was not 

possible due to the restrictions on the use and availability of these chemicals. The methods 

provided for this verification test were not optimized or modified for sensitivity and therefore 

may not represent the most optimal performance of the CT-1128 for a particular target 

contaminant. It is also important to note that the results of the verification test reflect the 

performance of the SPME sample preparation as well as the analysis by the CT-1128. Operator 

experience with SPME will therefore be beneficial to using the technique in tandem with the CT1128. 

36 
Though a recurring GC oven temperature error was observed during testing, the CT-1128 did not 

require any extensive maintenance during the verification test. The operator replaced the 

injection port septum each day as recommended by the vendor. On several occasions, leaks were 

suspected. Detection and remedial actions can take significant time. During the field test, 

detecting a small leak that seemed to contribute to a large amount of air and water took several 

hours. After a suspect copper gas line for the external helium gas cylinder was replaced, it took 

additional time to remove the water that had been introduced from the humid environment. It 

was noted that the SPME use resulted in great wear and tear on the septum, often resulting in a 

cored septum which could serve as a leak. It is therefore advisable to replace the septum at the 

end of each testing day. Such situations coupled with daily preparation and sample run times, 

which ranged from 22 minutes to 32 minutes, can have a significant impact on sample 

throughput. Typically, the daily procedures recommended for operation lasted approximately one 

hour. These activities, performed on a system that has reached thermal equilibrium, include a 

bakeout procedure, daily mass tuning, and an air/water check. If the system is not at equilibrium 

such as when it has been first deployed in the field, it is necessary to allow for two hours for 

thermal equilibration after achieving vacuum. Though it is possible to sequence the analytical 

steps to maximize sample throughput (e.g., exposing the SPME to absorb analytes for the next 

sample while the GC oven temperature is ramping down ), average sample throughput during 

verification testing was 11 samples per each ten hour working day, translating to approximately 

one sample per hour. Operational costs for the verification test included UHP helium, SPME 

vials, crimp seals, SPME fibers, and disposable stir bars. For 100 samples, the total cost for these 

supplies was approximately $914. The GC column and standard chemicals were not included in 

this cost. 

During the verification test, the operator occasionally observed errors for the column temperature 

readback. The problem seemed to be intermittent and erratic (alternating from low to correct to 

high reading). Inconsistent retention times supported that the problem was not merely a faulty 

readback, but actual variation in the GC oven temperature. Based on the technical support 

provided by the vendor, a faulty thermocouple was suspected. In addition to providing 

troubleshooting support, the vendor provided application support for target contaminants. 

37 
Chapter 7

Performance Summary

As shown in Table 7-1, benzene accuracy was considerably higher than ideal (100%) at 172% 

because of a change in response several days after establishing the calibration curve. Toluene 

(which had the lowest accuracy of the BTEX chemicals) exhibited significant over-recoveries, 

with an overall mean R of 440%, though accuracy for ethylbenzene and xylenes (total) was close 

to 100%. The mean R for 2,4-D and dicrotophos was 62% and 143%, respectively. For GB, the 

accuracy was close to ideal at 108%. For GD, the R was acceptable at 75%. The mean R for VX 

was 109%, though the concentrations tested were significantly higher than the LD50 for this 

CWA. 

Table 7-1. Summary of Accuracy, Precision, Linearity, and Stability 

Contaminant Accuracy Precision Linearity Stability 

Mean R Mean RSD r

2

 of curve Mean RPD 

benzene 172% 10% 1.000 27% 

toluene 440% 43% 1.000 52% 

ethylbenzene 104% 16% 1.000 9% 

xylenes (total) 103% 10% 1.000 12% 

2,4-D 62% 21% 0.921 35% 

dicrotophos 143% 42% 0.999 92% 

GB 108% 24% 1.000 48% 

GD 75% 14% 1.000 27% 

VX 109% 15% 0.959 27% 

Table 7-1 also shows that across all sample matrices, precision, as measured by RSD of 

replicates, ranged from 10% RSD for benzene to 43% RSD for toluene. 

The calibration curves of seven of the nine contaminants had coefficients of determination (r2

) of 

0.999 or greater. The exceptions were those contaminants for which the provided methods lacked 

sensitivity—2,4-D and VX (r2

 of 0.921 and 0.959, respectively), though for all contaminants, r2 

values were greater than 0.920. 

Instrument stability, in terms of the mean RPD of prepared sample replicates, ranged from 9% 

average RPD for ethylbenzene (with a SD of 5%) to 92% for dicrotophos (with a SD of 80%). 

38 
Only two contaminants, ethylbenzene and xylenes (average RPD of 9% and 12%, respectively), 

had average RPDs less than 20%, while toluene and dicrotophos had RPDs significantly greater 

than 20% (52% and 92%, respectively). Table 7-2 summarizes the results of testing for matrix 

effects on the analyses performed on the CT-1128. 

Table 7-2. Summary of Matrix Effects Observed 

Contaminant 

Matrix Effect(a) from Potential Interferents 9 = observed 

DW1 DW2 DW3 DW4 

Weakly 

Buffered 

Water 

Strongly 

Buffered 

Water 

THMs 

Spiked 

Water 

benzene • • 

toluene • • • • 

ethylbenzene • 

xylenes • 

2,4-D • • • • • 

dicrotophos • • • • • 

GB • • • 

GD • • • • • 

VX ND ND ND ND ND ND ND 

(a) matrix effect defined as recovery outside range of 70-130% of average response of daily PT samples 

ND = no data; VX matrix testing was not performed due to lack of sensitivity for this contaminant using the vendor 

provided method 

Table 7-2 shows that a matrix effect was present with the strong buffer matrix, which gave Rs 

outside the 70% to 130% range for all eight target contaminants tested. DW3 also showed matrix 

effects for five of the eight contaminants, which may be due to its origin as a groundwater 

sample. VX was not tested for potential matrix and interference effects because of the lack of 

sensitivity of the provided method. Table 7-3 shows the results of sensitivity testing of the CT1128. 

Table 7-3. Results of CT-1128 Sensitivity Testing for Target Contaminants 

Contaminant 

Concentration 

of Interest 

(mg/L) 

Sufficient Sensitivity 

to Detect Conc. of 

Interest 

benzene 0.005 Yes 

toluene 1 Yes 

ethylbenzene 0.7 Yes 

xylenes 10 Yes 

2,4-D 0.07 No 

dicrotophos 1400 Yes 

GB 20 Yes 

GD 1.4 Yes 

VX 2.1 No 

39 
Table 7-2 shows that with the exception of VX and 2,4-D (for which the provided methods 

lacked sensitivity), the sensitivity of the CT-1128 was sufficient to detect the target contaminants 

at the concentrations of interest, i.e., at LD50 or MCL concentrations. 

Because the CT-1128 requires approximately two hours to equilibrate once electrical power and 

gas have been supplied, it should be kept on standby (under vacuum and thermally equilibrated) 

as long as possible when time is a critical factor for analyzing field samples. Mobilization in the 

field is straightforward, and the CT-1128 requires only a source of electrical power for several 

hours of field deployment when used with its on-board hydrogen canister for a source of carrier 

gas. During the non-laboratory testing, the coefficients of determination (r2

) achieved in the field 

for benzene, toluene, ethylbenzene, and xylenes were 1.000, 0.996, 0.998, and 1.000, 

respectively, and the recoveries of a blind test water sample were 108%, 23%, 135%, and 121%, 

respectively. 

The CT-1128 did not require extensive maintenance during the verification test. On several 

occasions, leaks were suspected, and detection and remediation took a significant amount of time 

(as it typically does with any GC-MS system). Typical extraction and sample run times ranged 

from 22 minutes to 32 minutes. The daily procedures recommended for operation during 

verification testing (e.g., mass tuning, air/water check, and SPME fiber/GC column bakeout) 

lasted approximately one hour. Average sample throughput during verification testing was 11 

samples per 10-hour working day, or approximately one sample per hour. For 100 samples, the 

total cost for supplies was approximately $914, not including the GC column and standard 

chemicals. At the time of testing, the cost of the CT-1128 GC-MS system, with optional SPME 

stirrer/heater, was $140,000. 

It is important to note that the results of the verification test reflect the performance of the SPME 

sample preparation as well as the analytical results generated by the CT-1128. The methods 

provided for this verification test were not optimized or modified for sensitivity by the vendor 

prior to use in the verification test and therefore may not represent the most optimal performance 

of the CT-1128 for a particular target contaminant. Operator experience with SPME would 

therefore be beneficial to using the technique in conjunction with the CT-1128. 

40 
Chapter 8

References

1. Test/QA Plan for Verification of Mobile Mass Spectrometers, Battelle, Columbus, Ohio, 

July 2005. 

2. EPA-600-R-93/100. EPA Method 180.1. Turbidity (Nephelometric), Methods for the 

Determination of Inorganic Substances in Environmental Samples. 1993. 

3. American Public Health Association, et al. Standard Methods for Examination of Water and 

Wastewater. 19th Edition. 1997. Washington D.C. 

4. EPA 600/4-79/020 Method 150.1. pH, Electrometric Method.. 1982. 

5. EPA 600/R-94/111 Method 200.8. Determination of Trace Metals by Inductively Coupled 

Plasma - Mass Spectrometry. 1994. 

6. EPA 600/4-79/020 Method 130.2. Hardness, Total (mg/L as CaCO3) Titrimetric, EDTA. 

1982. 

7. EPA 600/R-95/131. EPA Method 524.2. Purgeable Organic Compounds by Capillary 

Column GC/Mass Spectrometry. Methods for Determination of Organic Compounds in 

Drinking Water, Supplement III. 1995. 

8. EPA 600/R-95/131. EPA Method 552.2. Haloacetic Acids and Dalapon by Liquid-Liquid 

Extraction, Derivatization and GC with Electron Capture Detector. Methods for the 

Determination of Organic Compounds in Drinking Water, Supplement III. 1995. 

9. Battelle SOP HMRC-IV-118-05: Standard Operating Procedure for the Determination of 

CA in Wastewater. 

10. EPA 600/R-95/131. EPA Method 515.1. Chlorinated Acids in Water by Gas 

Chromatography with an Electron Capture Detector. Methods for Determination of 

Organic Compounds in Drinking Water, Supplement III. 1995. 

41 
11. Quality Management Plan (QMP) for the ETV Advanced Monitoring Systems Center, 

Version 5.0, U.S. EPA Environmental Technology Verification Program, Battelle, 

Columbus, Ohio, March 2004. 

12. “National Primary Drinking Water Regulations” (40 CFR 141), U.S. Environmental 

Protection Agency, Office of Ground Water and Drinking Water (OGWDW), July 1, 2002. 

42