1 presented by wayne einfeld and gary brown sandia national laboratories albuquerque, new mexico usa...

1

presented by

Wayne Einfeld and Gary BrownSandia National Laboratories

Albuquerque, New Mexico USA

Eric KoglinUnited States Environmental Protection Agency

Las Vegas, Nevada USA

Technology Performance Characteristics

for the On-Site Measurement

of Chlorinated Volatile Organic

Compoundsin

Groundwater

2

Presentation Overview

A US EPA Environmental Technology Verification test of field-portable water monitoring instruments is described.

Test results are presented which include the features and performance characteristics of five different on-site instrumental analysis methods for the measurement of chlorinated VOCs in groundwater at contaminated sites.

3

Presentation Outline

Overview of ETV Program and the Site

Characterization and Monitoring

Technology Center

Technology Overviews

Verification Test Design

Verification Test Results

Summary and Conclusions

4

Established by EPA to verify the performance of innovative environmental technologies

Accelerates acceptance and use of improved, cost-effective technologies

Public and private partners to test technologies under EPA sponsorship and oversight

Six Centers including the Site Characterization and Monitoring Technologies Center (SCMT)

Site Characterization and Monitoring Technology Center has Sandia National Laboratories and Oak Ridge National Laboratory as verification testing partners

Environmental Technology Verification (ETV) Program

5

Site Characterization and Monitoring Technologies Center

Our Technology Focus . . .

Verify the performance of technologies that

can be used for generating real-time data or

information to support monitoring of human

and ecosystem health, assessing real or

potential exposure to environmental

contaminants and hazards, for monitoring

environmental conditions, and characterizing

(physically and chemically) contaminated sites

6

SCMT Center Goals

Accelerate the use and acceptance of innovative environmental monitoring and characterization technologies

Rigorous, statistically-defensible testing under actual field conditions

Provide reliable, high-quality performance information

Leverage federal resources and expertise

7

What does Verification Mean?

To establish or prove the truth of the

performance of a technology under specific,

predetermined criteria or protocols and adequate

data quality assurance procedures.

8

SCMT Technology Areas

Field analytical technologies– Field portable X-Ray fluorescence

spectrometers– Field portable gas chromatograph/mass

spectrometers– Immunoassay kits– Field portable gas chromatographs– Fiber optic chemical sensors– Alpha detectors– Colorimetric test kits

9

SCMT Technology Areas cont’d

Decision support software systems Physical characterization (e.g., geophysical

methods, direct-push systems) Soil, soil gas, groundwater, surface water,

and sediment sampling methods Technologies for assessing contaminated

structures Monitoring bioremediation and natural

attenuation Toxicity screening methods

10

Technology Verification Process

VerificationTest

Planning

VerificationTest

Planning

FieldTesting

FieldTesting

Data Collectionand Validation

Data Collectionand Validation

ReportPreparation

ReportPreparation

FinalReport &

VerificationStatement

FinalReport &

VerificationStatement

11

Verification Test Plan Development

Verification Test Plan

12

Verification Org. coordinates

Vendors operate their instruments

Testing at two sites or conditions

“Blind” sample analysis

QA audits during field tests

Verification Testing in the Field

13

Technology Verification Report Contents

Verification Statement

Technology Description

Site and Design Description

Reference Laboratory Data Validation

Verification Test Results

Field Observations and Cost Summary

Technology Update

14

Verification of Field Analytical Techniques

for the Measurement VOCs in Water

Goal: Verify field analytical techniques capable of detecting and quantifying chlorinated VOCs in water

Demonstration objectives:

– Obtain performance information using quality control and field samples

– Compare technology results with conventional laboratory results

– Determine logistical requirements for technology use

Data used in this presentation is taken from from published ETV reports (www.epa.gov/etv)

15

Five Technologies Were Tested

16

Why use these technologies?

Faster, cheaper, better site screening and routine ground water monitoring

Quick-turnaround sampling and analysis enables on-site decisions and dynamic workplans

Less sample handling and paperwork

Reapplication of existing equipment

17

How might these technologies be used?

Field analytical support for direct push investigations

Preliminary groundwater screening at new or existing

wells

Real-time monitoring for plume migration/barrier wall

performance

Routine groundwater monitoring programs for known

compounds at relatively high contamination levels (>10

ug/L)

Soil vapor analysis

Waste water outfall monitoring

18

Getting Sample to the Instrument

Equilibrium Headspace- simple- less sensitive- HAPSITE, Voyager, Multi-gas

Monitor

Purge-and-Trap/Thermal Desorption

- more complex- more sensitive- Scentograph Plus II, EST Model 4100

19

Equilibrium HeadspaceHenry’s LawAt constant temperature:

[VOC]gas __________ = Henry’s Constant [VOC]liq

Henry’s Constant is compound-specific and is determined by the solubility of the compound in water

Less soluble > Higher headspace concentration More soluble > Lower headspace concentration

A gas sample is withdrawn from the headspace and analyzed by GC. The water concentration is calculated from the gas concentration using Henry’s Constant

Gas PhaseVOC Concentration

Liquid PhaseVOC Concentration

20

Dynamic Headspace (Purge-and-Trap)

Purge Gas

Helium

or

Nitrogen

Step 1Purge VOCs from solution and trap on sorbent

Step 2Heat the sorbent trap and sweep the VOCs off the sorbent with the carrier gas

20

Carrier

Gas

21

Gas Chromatography (GC)

Separates a mixture of compounds (usually organic)

Relies on differing solubilities of the analytes in an organic compound (stationary phase) lining the column wall

Detector at end of column allows separated compounds to be quantified

Retention time and detector response enable compound identification and quantification

22

Headspace/Gas Chromatography

23

Perkin-Elmer, Voyager

Description: Field-portable GC with multiple columns and dual ECD and PID detectors, isothermal operation

Size, Weight: Small, 48 pounds (with accessories)Sample handling: Completely manualSample throughput: 1-3 samples/hrData processing: pre-programmed automated methods, printed

outputCalibration: pre-deployment calibration, daily check standards Power: Battery or AC Cost: $24KAccessories: Carrier gases, optional PC, syringes, water bathOperator training: 1-2 hours for a chemical technician

24


25

Electron Capture Detector

A “standing current” is produced in the detector by the interaction of a radioactive electron source with the carrier gas.

When electronegative compounds enter the detector they “capture” the electrons and cause a measurable change in the standing current.

26

Photoionization Detector

A UV lamp is used to irradiate a heated ionization chamber at the end of a GC column

The UV energy ionizes many organic molecules through a photoionization reaction:

R + h = R+ + e-

The resulting ion current is sensed by an electrometer and is used to quantify the amount of material present

Electrometer

+

–

Power Supply

From GCColumn

Exhaust

UV LampHeated Ionization Chamber

27

Sentex Systems Inc., Scentograph Plus II

Description: Field-portable, purge-and-trap GC with micro-argon ion and/or electron capture detector, isothermal or temperature program operation

Size, Weight: Moderate, 80 poundsSample handling: Completely automatedSample Throughput: 2 samples/hourData processing: pre-programmed automated methods, printed

output not readily availableCalibration: Daily three-point, daily check standardsPower: Battery or AC Cost: $35KAccessories: Carrier gases, PCOperator training: Moderate

28


29

Micro Argon Ion Detector

The detector contains a tritium foil that is used to irradiate the argon carrier gas

Some of the argon molecules become excited (metastable).

The metastable argon ionize the organics

Ar + e– = Ar*

Ar* + R = R+ + e–

The resulting ion current is sensed by an electrometer and is used to quantify the amount of organic material present

Electrometer

+

–

Argon carrier gasfrom GC column

ExhaustTritium Foil

30

Electronic Sensor Technology Inc., Model 4100

Description: Field-portable, purge-and-trap GC with surface acoustic wave detector

Size, Weight: Moderate, 35 pounds

Sample Handling: Partially automated

Sample Throughput: 2-3 samples/hour

Data processing: pre-programmed automated methods, printed output

Calibration: pre-deployment 3-point calibration, periodic check standards, internal standard

Power: Battery or AC

Cost: $25K

Accessories: Carrier gases, PC

Operator training: 1 day for experienced chemical technician

31

Electronic Sensor Technology Inc., Model 4100

32

Surface Acoustic Wave Detector

A surface acoustic wave (SAW) detector operates much like a quartz crystal detector. An AC voltage at the input transducer causes an acoustic wave to propagate across a crystal surface to the output transducer.

Adding mass, such as an analyte from the end of a GC column, onto the detector surface causes a measurable change in the properties of the acoustic wave.

33

Inficon Inc., HAPSITE

Description: Field-portable GC-MS and Headspace Sampling Accessory

Size, Weight: Moderate, 75 poundsSample Handling: Partially automatedSample Throughput: 2-3 samples per hourData Processing: pre-programmed automated methods, printed

output Calibration: pre-deployment multi-point, periodic check standard,

internal and surrogate standards, daily MS tune checkPower: Battery or AC Cost: $75-95KAccessories: Calibration and carrier gases, PCOperator training: 1 day of training for an experienced chemical technician

34

Inficon Inc., HAPSITE

35

GC-Mass Spectrometry

Quadrupole Mass Selective Detector

An electron beam ionizes compounds exiting the GC column

The quadrupole filter allows ions of specific mass to pass through the filter and strike the ion collector.

The mass selectivity of the filter can be continuously scanned over a pre-determined range by changing the dc and rf settings of the filter.

36

Innova AirTech Instruments Type 1312 Multi-gas Monitor

Description: Field-portable, photoacoustic infrared bandpass spectrometer

Size, Weight: Small, 30 pounds

Sample Handling: Partially automated

Sample Throughput: 1-2 samples/hr

Data Processing: Automated method, manual recording of data necessary, no printed report

Calibration: Factory calibration, no daily check standards

Power: Battery or AC

Cost: $28-35K

Accessories: Headspace flask, stir plate, tubing

Operator training: Several hours for a field technician

37


38

Photoacoustic Spectroscopy

Chopped (intermittent) bandpass-filtered infrared radiation is passed through a cell containing the gases of interest.

The target gases absorb the radiation. The absorption is accompanied by a rise and fall in temperature (pressure) in the cell at the chopping frequency.

This pressure cycle or acoustic signal is detected by two sensitive microphones. The intensity of the pressure cycle is related to the target gas concentration.

39

Verification Test Design Elements

Different Environmental Conditions– Testing at two contaminated sites with groundwater wells (Savannah River, SC and McClellan AFB, CA) – Historical sampling data used to select GW wells

A Blend of Field and QA Samples– Performance evaluation (PE), 42 samples per site– Groundwater (GW), 33 samples per site– Blank samples, 8 per site

Reference Laboratory Analyses– Splits of all samples analyzed by an off-site reference

laboratory– US EPA Method 8260 (Purge-and-trap GC-MS)

40

Verification Test Design Elements cont’d

PE Mix 1 - Purgeable ASupelco Cat. No. 4-8059

Lot LA68271

PE Mix 2 - VOC 3Supelco Cat. No. 4-8779

Lot LA64701

PE Mix 3 - Purgeable BSupelco Cat. No. 4-8058

Lot LA 63978

Trichlorofluoromethane 1,1-Dichloropropene 1,2-Dichloroethane

1,1-Dichloroethane 1,2-Dichloroethane 1,1,2,2-Tetrachloroethane

Dichloromethane Trichloroethene cis-1,3-Dichloropropene

1,1-Dichloroethene 1,2-Dichloropropane trans-1,3-Dichloropropene

Chloroform 1,1,2-Trichloroethane trans-1,2-Dichloroethene

Carbon tetrachloride 1,3-Dichloropropane 1,1,1-Trichloroethane

Trichloroethene 1,2-Dibromoethane Benzene

1,2-Dichloropropane 1,1,1,2-Tetrachloroethane Bromodichloromethane

1,1,2-Trichloroethane 1,1,2,2-Tetrachloroethane Toluene

Tetrachloroethene 1,2,3-Trichloropropane Ethyl benzene

Dibromochloromethane 1,2-Dibromo-3-chloropropane Bromoform

Chlorobenzene cis-1,3-Dichloropropene

1,2-Dichlorobenzene trans-1,3-Dichloropropene

2-Chloroethyl vinyl ether Hexachlorobutadiene

Multiple VOC Compounds

Participating technologies were not calibrated for all these compounds

41

Verification Test Design Elements cont’d

A Wide Concentration Range of Compounds

– PE Samples: 10 µg/L to >1000 µg/L

– GW Samples: 5 µg/L to > 1000 µg/L

Blind Replicate Samples

– Triple or quadruplicate splits of all GW and PE samples

– for determination of instrument precision

42

A Challenging Test Sample Matrix

A Challenging Test Sample Matrix

65 environmental groundwater samples from both sites

84 performance evaluation (PE) water samples mixed and distributed onsite

8 blank samples ~160 samples analyzed per

technology over ~ 8 days Over 9000 individual compound

analyses!

Groundwater

PE + Blanks

43

Field Sample PreparationPE Samples Performance Evaluation samples were mixed in a 10-L carboy in an onsite mobile laboratory and then dispensed into 40-mL VOA vials Each of the five technologies and reference lab were given 4 replicates from all PE mixtures

GW Samples 10 liters of groundwater was sampled into a glass carboy from various monitoring wells with downhole electric pumps Carboy contents were mixed and then dispensed into 40-mL VOA vials at the wellhead. Replicate samples were distributed to all participants and the reference laboratory

44

Sample Distribution

GW Samples

Blank Samples

PE SamplesHAPSITE

VOYAGER

Model 4100

Scentograph Plus II

Multi-gas Monitor

Reference Lab

Each sample delivered intriplicate or quadruplicate

45

Definition of Terms

Precision Relative standard deviation from replicate samples

Accuracy Average percent recovery of a known test sample or absolute percent difference from a known

Comparability Percent difference of results relative to reference laboratory results

Detection Limit Method Detection Limit or Practical Quantitation Limit

Sample Samples per hour Throughput

False Positive Frequency that detects are reported for blank samples

False Negative Frequency that no-detects are reported for compounds at or near the 5 ug/L regulatory limit

46

Key Instrument Performance Parameters in this Test

Accuracy - percent recovery

Precision - relative standard deviation

Comparability to reference - absolute percent difference

False positive/negative - at blank and 10 ug/L conc. levels

Sample throughput - samples per hour

Versatility - number of compounds detected

Ease of use - through field observation

Operator training requirements -through field

observation

47

ETV doesn’t compare technologies

In a policy of fairness and

objectivity, ETV doesn’t pick

technology winners and losers

Technologies are varied and their

application is usually site- and

application-specific

The site user is best-suited to

match site needs with technology

capabilities

Side-by-side comparisons, if

required, are left to the user

Brand X Brand Y

???

48

How the results are presented

Presentation by instrument

Performance CharacteristicsFalse +/-AccuracyPrecisionComparison with Reference Lab

Summarized results are necessary (lots of data in reports!) Performance for TCE and PCE is emphasized

TechnologyPerformanceResults

49

Perkin Elmer Voyager False +/-

False positive rate in 16 blanks: 19%False negatives for SRS site (10 Samples at 10 g/L):

Compound False Negative Rate (%)1,1-Dichloroethene 0 Dichloromethane 0 Chloroform 100Carbon tetrachloride 0 1,2-Dichloropropane 80Trichloroethene 01,1,2-Trichloroethane 100Dibromochloromethane 90Tetrachloroethene 0 Chlorobenzene 0 1,1-Dichloroethane No calibration1,2-Dichlorobenzene No calibration

50

Voyager Summary Precision

% RSD VoyagerTCE

Ref LabTCE

VoyagerPCE

Ref LabPCE

Median 15 6 ** 6

Minimum 7 1 9 2

Maximum 71 12 ** 22

N SampleSets

8 16 8 11

Combined data from PE samples at both sites** Voyager did not detect PCE in 7 of 8 sets

51

Average Voyager Recovery for Selected Compounds

0 50 100 150 200 250 300 350 400

TCE @ SRS

TCE @ MCL

PCE @ SRS

PCE @MCL

12DCA @ SRS

12DCA @ MCL

Co

mp

ou

nd

an

d S

ite

Average Percent Recovery

Low Conc. (~100 ug/L)

Mid Conc. (~200 ug/L)

High Conc. (~800 ug/L)

High/Low Mix Conc.

52

Voyager Summary Accuracy

Compound % RecoveryRange

Trichloroethene 92–344

1,2-Dichloroethane 34–170

1,2-Dichloropropane 34–170

1,1,2-Trichloroethane1,2-Dichloropropane

50–116

Tetrachloroethene 1–124

Trans-1,3-Dichloropropane

72–162

For selected target compounds

53

Scatter Plot Comparisons with Reference Lab

Example scatter plots shown for both sites combined A total of 20 TCE and 20 PCE detects by the reference

lab at all concentration ranges at both sites Only TCE and PCE results below 500 ug/L are plotted False negatives reported by technology are also shown Diagonal line in plot is the zero-bias line

54

Perkin Elmer Voyager vs. Lab Reference

TCE and PCE in groundwater samples at both sites

0

50

100

150

200

250

300

350

400

450

500

0 100 200 300 400 500

Ref Lab Conc. (ug/L)

Vo

ya

ge

r C

on

c. (

ug

/L)

TCE at SRS

TCE at MAFB

PCE at SRS

PCE at MAFB

0 False Negatives Reported

55

Perkin-Elmer, VoyagerPerformance Summary

False negative rate: low for TCE and PCE

Precision: <20% RSD for TCE

Undetermined for PCE

Accuracy: 90-340% TCE Recovery

1-120% PCE Recovery

Reference Lab Comparison: Biased high for TCE and PCE

56

Scentograph Plus II False +/-

Compound False Negative Rate (%)1,1-Dichloroethene 0Dichloromethane 0Carbon tetrachloride 0 1,2-Dichloropropane 30Trichloroethene 01,1,2-Trichloroethane 0 Tetrachloroethene 0 Chlorobenzene 0 2-Chloroethyl vinyl ether No calibrationDibromochloromethane No calibrationTrichlorofluoromethane No calibration1,1-Dichloroethane No calibration1,2-Dichlorobenzene No calibration


57

Scentograph II Summary Precision

% RSD ScentogrTCE

Ref LabTCE

ScentogrPCE

Ref LabPCE

Median 6 6 7 6

Minimum 0 1 3 2

Maximum 17 12 13 22

N SampleSets

8 16 4 11

58

Average Scentograph Recovery for Selected Compounds

0 20 40 60 80 100 120 140 160 180 200

TCE @ SRS

TCE @ MCL

PCE @ SRS

PCE @MCL

12DCA @ SRS

12DCA @ MCL

Co

mp

ou

nd

an

d S

ite





High/Low Mix Conc.

59

Scentograph Plus II Summary Accuracy




1,2-Dichloropropane

84–122

1,1,2-Trichloroethane

85–116


trans-1,3-Dichloropropane

83–124


60

Sentex Scentograph Plus II vs. Lab Reference

0

50

100

150

200

250

300

350

400

450

500

0 100 200 300 400 500


Sc

en

tog

rap

h C

on

c. (

ug

/L)

TCE at SRS

TCE at MAFB

PCE at SRS

PCE at MAFB



61

Sentex Scentograph Plus II

Performance Summary



<10% RSD for PCE


95-115% PCE Recovery

Reference Lab Comparison: No bias for TCE and PCE

62

EST Model 4100 II False +/-

Compound False Negative Rate (%)1,1-Dichloroethene 100Dichloromethane No calibrationChloroform 100Carbon tetrachloride 1001,2-Dichloropropane 100Trichloroethene 01,1,2-Trichloroethane 100Dibromochloromethane No calibrationTetrachloroethene 0Chlorobenzene 01,1-Dichloroethane 1001,2-Dichlorobenzene 100


63

Model 4100 Summary Precision

% RSD Model 4100TCE**

Ref LabTCE

Model 4100PCE

Ref LabPCE

Median 10 6 12 6

Minimum 2 1 6 2

Maximum 28 12 22 22

N SampleSets

8 16 6 11

**TCE reported as a co-eluter with 1,2 dichloropropane

64

Average Model 4100 Recovery for Selected Compounds

0 20 40 60 80 100 120 140 160 180 200

TCE @ SRS

TCE @ MCL

PCE @ SRS

PCE @MCL

112TCA @ SRS

112TCA @ MCL

Co

mp

ou

nd

an

d S

ite





High/Low Mix Conc.

65

Model 4100 Summary Accuracy




1,2,3-Trichloropropane 49–174

1,1,2-Trichloroethane 57–118


trans-1,3-Dichloropropene

57–145


66

EST Model 4100 vs. Lab Reference


0

50

100

150

200

250

300

350

400

450

500

0 100 200 300 400 500


Mo

de

l 41

00

Co

nc

. (u

g/L

)

TCE at SRS

TCE at MAFB

PCE at SRS

PCE at MAFB


67

EST Model 4100Performance Summary



<20% RSD for PCE


35-70% PCE Recovery

Reference Lab Comparison: Biased low for TCE and PCE

68

Inficon HAPSITE False +/-

Compound False Negative Rate (%)1,1-Dichloroethene 0Dichloromethane 01,1-Dichloroethane 0Chloroform 0Carbon tetrachloride 101,2-Dichloropropane 0Trichloroethene 01,1,2-Trichloroethane 40Dibromochloromethane 20Tetrachloroethene 40Chlorobenzene 101,2-Dichlorobenzene No calibration


69

HAPSITE Summary Precision

% RSD HAPSITETCE

Ref LabTCE

HAPSITEPCE

Ref LabPCE

Median 14 6 15 6

Minimum 7 1 6 2

Maximum 18 12 22 22

N SampleSets

8 16 6 11

70

Average HAPSITE Recovery for Selected Compounds

0 20 40 60 80 100 120 140 160 180 200

TCE @ SRS

TCE @ MCL

PCE @ SRS

PCE @MCL

12DCA @ SRS

12DCA @ MCL

Co

mp

ou

nd

an

d S

ite





High/Low Mix Conc.

71

HAPSITE Summary Accuracy




1,1,2-Trichloroethane 79–120



trans-1,3-Dichloropropane

85–101


72

Inficon HAPSITE vs. Lab Reference

0

50

100

150

200

250

300

350

400

450

500

0 100 200 300 400 500


HA

PS

ITE

Co

nc

. (u

g/L

)

TCE at SRS

TCE at MAFB

PCE at SRS

PCE at MAFB



73

Inficon HAPSITEPerformance Summary

False negative rate: low for TCE, high for PCE


<15% RSD for PCE


70-95% PCE Recovery


74

Innova Multi-gas Monitor False +/-

False positive rate in 16 blanks: 13%

False negatives for SRS site:(6 samples at 10 g/L, TCE and PCE only)

Compound False Negative Rate (%)

Trichloroethene 0Tetrachloroethene 50

75

Multi-gas Monitor Summary Precision

% RSD Multi-gasTCE

Ref LabTCE

Multi-gasPCE

Ref LabPCE

Median 16 6 13 6

Minimum 4 1 5 2

Maximum 22 12 46 22

N SampleSets

13 16 13 11

76

Average Multi-gas Monitor Recovery for TCE and PCE

0 20 40 60 80 100 120 140 160 180 200

TCE @ SRS

TCE @ MCL

PCE @ SRS

PCE @ MCL

Co

mp

ou

nd

an

d S

ite


Low 1 (~50 ug/L)

Low 2 (~100 ug/L)

Mid 1 (~200 ug/L)

Mid 2 (~250 ug/L)

High 1 (~400 ug/L)

High 2 (~700 ug/L)

VHigh (~1250 ug/L)

77

Multi-gas Monitor Summary Accuracy




For TCE and PCE

78

Innova Multi-gas Monitor vs. Lab Reference


0

50

100

150

200

250

300

350

400

450

500

0 100 200 300 400 500


Mu

lti-

ga

s M

on

ito

r C

on

c. (

ug

/L)

TCE at SRS

TCE at MAFB

PCE at SRS

PCE at MAFB


79

Innova Multi-gas Monitor

Performance Summary

False negative rate: low for TCE, high for PCE


<15% RSD for PCE


50-110% PCE Recovery


80


Advantages Lightweight and small Sensitive and selective for a variety of VOCs Three columns and dual detectors (PID/ECD) can

help in the identification of unknown compounds Detects most VOCs, including halogenated and

non-halogenated aliphatic and aromatic hydrocarbons

Instrument is easy to operate

81


Limitations EC detector requires radioactive permit/license Isothermal column only -- co-elution of analytes

possible in complex samples Somewhat cumbersome manual sample handling

and injection is required Equilibrium headspace method limits sensitivity for

some VOC compounds Equilibrium headspace method used in this test

needed further development and negatively influenced the results

82


Advantages Purge-and-trap system with MAID offers high

sensitivity -- sub-ppb detection for most VOCs

Isothermal or temperature programmable operation

Dual detector option can give versatility:

– microargon ionization (MAID)

– electron capture detector (ECD)

Virtually no sample handling required

System could be fully automated to run unattended

83


Limitations Maximum operating temperature of 179 o C

MAID and ECD detectors contain tritium and may require a state permit/license

At the time of the test, control and analysis software was dated and in need of an upgrade

Only moderately portable -- two bulky packages plus accessories

84

Electronic Sensor Technology Inc.,Model 4100

Advantages Compact portable package

Purge-and-trap feature enables improved detection levels over equilibrium headspace methods

Minimal sample handling requirements

Universal (mass sensitive) SAW detector

Wide detector dynamic range (greater than 104)

Fast throughput (less than 30-second chromatographic total elution time)

85

Limitations With fast analysis times, co-elution of

compounds is possible Data analysis for complex samples is not fully

automated and requires considerable operator intervention

Operator experience in chromatography desirable for complex samples

Electronic Sensor Technology Inc.Model 4100

86

Inficon, HAPSITE

Advantages Headspace accessory enables automatic GC

injection

Unknown compound identification with on-board mass spectral libraries

Highly versatile for unknown identification

Moderately portable (3 pieces including PC) in light of the analytical power of the instrument

87

Inficon, HAPSITE

Limitations Considerable sample handling is required

Isothermal operation only

Compound sensitivity is limited by equilibrium headspace considerations

Instrument is relatively expensive

Maintenance costs can be high (getter pump)

88


Advantages Detection limits for TCE and PCE in water are

in the low ppb range

Large dynamic range (6 orders of magnitude)

Small cell volume reduces volumes of samples and calibration gas

Instrument is easy to use

Calibrations are stable over many months

89


Limitations Some sample handling is required

The headspace flask accessory needs further development

Instrument must be factory calibrated for the compounds of interest

Compound sensitivity is limited by equilibrium headspace considerations

The presence of unknowns can cause erroneous results

90

ETV Site Characterization and Monitoring Technologies information is at the US EPA web site

www.epa.gov/etv

The web site contains: Test categories Test schedules Test plans Report summaries Complete reports Center news

For more information...

91

Links to Additional Resources

1 presented by wayne einfeld and gary brown sandia national laboratories albuquerque, new mexico usa...

Documents

oversight n n

directpush systems n

performance of technologies

groundwater slide

technology focus

expertise slide

actual field conditions

scmt center goals o