Application of Passive Sorbent
Techniques to the Measurement of
Naphthalene in Indoor Air
Heidi Hayes, Technical Director
March 26, 2015
AEHS San Diego, CA
www.airtoxics.com
Outline
•
Background
–
–
•
Selection of passive sampler configurations
Optimization for naphthalene
Chamber Studies
–
–
Generation of Uptake Rates
Low concentration naphthalene challenge
–
•
•
TO-15, TO-17, and passive
Conclusions
Next steps
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2
The Naphthalene Challenge
Residential Indoor Air Screening Level = 0.083 µg/m3*
Parameter
TO-15
TO-17
Passive
Reliability of equipment
Fair
Fair
Excellent
Ease of sample collection
Fair
Fair
Excellent
Sampling period – days to weeks
Limited
Limited
Excellent
Naphthalene performance at RSL
Marginal
Excellent
??
*USEPA Regional Screening Level (November 2014)
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3
Passive Sampling Concepts
Measured in lab
Analytical Sensitivity dependent on sorbent type
Analytical Result
(µg)
1000 mL
1L
X
X
1000 L
m3
Concentration
(µg/m3)
Uptake Rate
(mL/min)
X
Sampler Geometry specific
Sampling duration
(min)
Recorded in the field
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4
Passive Sampler Candidates
Sampler Geometries
Tube
Permeation
Badge
Radial
Sorbent
Higher
Analytical
Sensitivity
Lower
Sensitivity
Thermal
Desorption
Solvent
Extraction
Lowest
Uptake Rate
Highest
Uptake Rate
© 2015 Eurofins Air Toxics, Inc. All Rights Reserved
Sorbent Selection
Sorbent Category
Type
Retention
Desorption
Efficiency
Solvent Extraction
Charcoal
Excellent
Very Poor <20%
Carbon Molecular Sieves
(CMS)
Excellent
Poor
Strong graphitized carbon
blacks (Carbopack X)
Excellent
Marginal
Medium graphitized carbon
black (Carbopack B)
Excellent
Good
Weak porous polymer
(Tenax TA)
Excellent
Excellent
Thermal Desorption
© 2015 Eurofins Air Toxics, Inc. All Rights Reserved
Passive Sampler Candidates
Sampler Geometries
Tube
Permeation
Badge
Radial
Sorbent
Higher
Analytical
Sensitivity
Lower
Sensitivity
Tenax TA
Solvent
Extraction
Lowest
Uptake Rate
Highest
Uptake Rate
© 2015 Eurofins Air Toxics, Inc. All Rights Reserved
Passive Sampler Configuration
Radiello custom solution
•
•
Sorbent: Tenax TA Cartridge (RAD147)
Diffusive Body: High permeability (white RAD120)
•
•
•
Uptake rates for VOCs 60 to 80 mL/min
Routinely paired with charcoal sorbent, not thermal desorption
cartridge due to its high uptake rate.
Combination is used for phenol and cresol application.
White
Yellow – less
permeable
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8
Chamber Study – Uptake Rates
~80 µg/m3 Toluene (~20 ppbv)
~20 µg/m3 Naphthalene (~4 ppbv)
Permeation Device –
Toluene and
Naphthalene Vapors
Conditioned Air Flow
(2 LPM)
%RH = 50 + 5
Temp (deg C) = 23 + 2
TO-17
Radiello Samplers
TO-17
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Uptake Rate (mL/min)
Chamber Study – Uptake Rates
Toluene
Naphthalene
4 hours
8 hours
24 hours
Duration
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Low concentration challenge
~16 µg/m3 Toluene (4 ppbv)
~3.5 µg/m3 Naphthalene (0.6 ppbv)
Permeation Device –
Toluene and
Naphthalene Vapors
Conditioned Air Flow
(2 LPM)
%RH = 50 + 5
Temp (deg C) = 23 + 2
TO-17
TO-15
Radiello Samplers
3-day deployment
3 x 24-hr TO-15 samples collected.
TO-17 concentrations used as the control.
© 2015 Eurofins Air Toxics, Inc. All Rights Reserved
Low Concentration Results
C/C0
Toluene
Naphthalene
1.6
1.6
1.4
1.4
1.2
1.2
1
1
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
0
TO-17
TO-15
RAD147
TO-17
TO-15
RAD147
C0 = TO-17 Control Concentration
© 2015 Eurofins Air Toxics, Inc. All Rights Reserved
Conclusions
• TO-15 and RAD147 concentrations fell within 60-140% of
expected for sub-ppbv levels of naphthalene.
• TO-15 SIM naphthalene measurements showed greater
variability than TO-17 and RAD147.
• The Radial-Tenax combination is promising as a passive
sorbent solution for meeting indoor air naphthalene RSL over a
period of 1 to 3 days.
© 2015 Eurofins Air Toxics, Inc. All Rights Reserved
Next Steps
• Observed a general high bias for RAD147 over a 3-day period
•
•
Small, limited data set – is this trend repeatable?
Is the uptake rate at 3 days consistent with 24 hours?
• Field validation for Radial-Tenax configuration
•
•
•
Indoor air site with low-level naphthalene source
Verification of performance using concurrent TO-17 measurements
Duration to be evaluated: 1, 2, and 3 days.
• Determine uptake rates for other geometries paired with Tenax
to optimize passive sorbent solution for desired sampling
periods.
© 2015 Eurofins Air Toxics, Inc. All Rights Reserved
Questions
Heidi Hayes
[email protected]
916-605-3341
www.airtoxics.com
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