Air Toxics LTDLaboratory Services Since 1989

Field Evaluation of Diffusive Samplers for Indoor Air VOC Measurements

AIHce 2011

Heidi Hayes, Technical Director

Robert Mitzel, Vice-President

Business Development1201

Outline

• Introduction

• Study Objectives

• Sampler Selection

• Field Sampling

• Results

• Conclusions

Conventional Air Sampling

• Possible equipment failure• Requires experienced field

sampler• Short duration (~24 hours)• Expensive to ship

• Requires experienced field sampler

• Short duration (~8 hours)• Sorbent type and sample

volume selection is critical

Summa Canisters Pumped Sorbent Tubes

Passive Sampling

Practical Advantages• Reliable deployment with little training required• Unobtrusive• Inexpensive to ship

Technical Advantages• Capable of generating trace level RLs• Long-term time-integrated measurements

More representative indoor air concentrations and increased sensitivity are advantageous to health risk assessments.

Passive Sampling Concepts

Concentration (µg/m3)

Analytical Result(µg)

Uptake Rate(mL/min)

Sampling duration(min)

1000 mL1L

1000 Lm3

X

X X

Recorded in the fieldAvailable in literature

Dependent on Sampler Geometry

Measured in lab

Project Objectives

• Sample integration of 1 to 7 days

• Measurement of a wide VOC suite – Petroleum and chlorinated compounds

• Reporting limits comparable to TO-15 SIM (~0.1 µg/m3)

• Measured concentrations correlate with TO-15

Passive Samplers

Tube

Solvent

Membrane

ThermalDesorption

RadialBadge

SKC 5753M OVM

SKC ULTRA Radiello®145WMS®-

TDATD

Radiello®130WMS®-Charcoal

Sampling RateLowest Highest

Sampler Geometries

Sorbent

Passive Samplers

Tube

Solvent

Membrane

ThermalDesorption

RadialBadge

SKC ULTRA Radiello®145

Radiello®130

Sampler Geometries

Sorbent

Field Sampling – Case 1

• Indoor air samples collected

• Duration 3, 4, and/or 7 days

• Concurrent deployment– Radiello 130 – Charcoal– Radiello 145 – TD Sorbent– ULTRA III – TD sorbent

Results

Compound Sample ULTRA IIIRadiello-Charcoal

Radiello-TD %RSD

Indoor 1 0.46 0.33 0.29 25%Indoor 2 0.86 0.84 0.42 35%Indoor 3 1.0 0.70 0.54 31%Indoor 4 7.4 9.4 6.8 17%

Tetrachloroethene Indoor 4 2.9 3.0 3.7 14%

Trichloroethene

Concentration (µg/m3)

Good comparability was observed when detections on each sampler were sufficiently above their respective

reporting limits.

Results

•ULTRA III = 5-20 times greater sensitivity than the RAD-Charcoal.

•ULTRA III had validated sampling rates for chlorinated breakdown products whereas RAD-TD required estimated rates.

•Diffusive adsorption on the RAD-TD sorbent did not behave as predicted for these light VOCs (chloroform, 1,1-DCE) resulting in low bias. Stronger TD sorbent is required for these VOCs.

Results• One indoor air location was severely

impacted with chlorinated solvents (100 to 10,000 µg/m3)

• Sampling duration was 3 days.

• Both Radiello-TD and ULTRA III exceeded capacity & TD-GC/MS.

• Radiello-Charcoal had a higher capacity, and solvent extraction allowed for easy dilutions.

Field Sampling – Case 2

• Indoor air samples collected – 13 sites– Concurrent TO-15 cans & ULTRA III– Chlorinated solvents,petroleum products– 1 to 3 day duration

Results

Strong correlation between ULTRA III and TO-15 concentrations across 3 orders of magnitude and at

concentrations <0.1 µg/m3

Conclusions

• Each passive sampler evaluated provided quantitative VOC indoor air measurements for TCE and PCE over a period of up to 7 days.

• The larger surface area of charcoal provided an advantage over TD-sorbents when sampling high concentrations over multiple days.

Conclusions

• ULTRA III-TD and Radiello-TD provide greater sensitivity than the Radiello-Charcoal over the 1-7 day period.

• ULTRA III-TD provides a wider range of VOCs than Radiello-TD.

• ULTRA III has a built-in blank correction allowing for improved accuracy at trace levels.