air toxics ltd laboratory services since 1989 field evaluation of diffusive samplers for indoor air...
TRANSCRIPT
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.