Selecting the most suitable adsorbent for Air - Sigma

Transcription

Selecting the most suitable adsorbent for Air
Monitoring
Frank Michel, Jamie Brown
sigma-aldrich.com/analytical
© 2012 Sigma-Aldrich Co. All rights reserved.
Selecting an Adsorption Material
Questions to be asked:
• What and for what purpose needs to be determined?
• What are the requirements?
– Obeying official methods or norms
– Reliability of data (“court” proof)
– Duration of measurement
– Long term, short term (e.g. work place)
• Available equipment?
– Thermal desorber
– Pumps
– Analytical Instruments
Information resources
Official methods
• DIN, VDI
• International standards/norms (EN, ISO,…)
• NIOSH / OSHA / EPA
– http://www.osha.gov/dts/sltc/methods/toc.html
– http://www.cdc.gov/niosh/nmam/
– http://www.epa.gov/ttnamti1/airtox.html
Literature (e.g. journal articles)
Literature of supplier (applications, recommendations)
Analytical common sense / knowledge
Adsorbent Tubes - Media
Tubes
– Glass,
– Stainless steel
– (Plastic)
Adsorption Media
– Activated Coconut Charcoal
– Polymers
– Silica gel
– Florisil
– Graphitised Carbon Blacks
– Carbon Molecular Sieves
– Poly Urethane Foam (PUF)
– Coated Adsorbens
Adsorbent Tubes - Media
Tubes
– Glass,
– Stainless steel
– (Plastic)
Adsorption Media
– Activated Coconut Charcoal
– Polymers
– Silica gel
– Florisil
– Graphitised Carbon Blacks
– Carbon Molecular Sieves
– Poly Urethane Foam (PUF)
– Coated Adsorbens
Carbon Molecular Sieves History within Supelco
More than 20 year experience in preparing Carbon
adsorbents
Carbosieves
• First Family of Carbon molecular sieves (S-I, S-II, S-III)
• Carbosieve S-III one of strongest adsorbents
– Microporus only
– First CMS in air monitoring
Carboxenes (Introduced 1987)
• Carboxene-1000 highly efficient adsorbent
– Not as strong as S-III but far better kinetics
– Materials on Galileo and Titan Mission
Carbon Molecular Sieves
Carboxen-563
Carboxen-564
Carboxen-569
Carboxen-1000
Carboxen-1001
Carboxen-1002
Carboxen-1003
Carboxen-1016
Carboxen-1018
Carbosieve-SIII
Typical Characteristics:
• Spherical
• High surface area 400 to 1200 m2/g
• Designed to retain and release small
molecular weight compounds
• Max. desorption temperature >400°C
Carboxen-569, W. Engewald et al.,
Anal Bioanal Chem (2002) 373: 490–500
Relative Hydrophobicity of Carbon Molecular Sieves
Carboxen-1016
Carboxen-569, -1001, -1003
Retains
Less H2O
Carboxen-563, -564
Carboxen-1000
Carboxen-1012
Carboxen-1018, -1021, Carbosieve SIII
Retains
More H2O
If used in a humid atmosphere, a dry purge is typically
needed!!
Graphitized Carbons
Carbopack-F
Carbopack-C
Carbopack-Y
Carbopack-B
Carbopack-X
5 m2/g
10 m2/g
24 m2/g
100 m2/g
240 m2/g
Weakest
Strongest
Carbotrap-X, W. Engewald et al.,
Anal Bioanal Chem (2002) 373: 490–500
Typical Characteristics
Granular
Surface area: 5 to 240 m2/g
Designed to retain and release mid to large molecular weight compounds
Hydrophobic
Max. desorption temp. >400°C
Porous Polymers
Tenax TA
(35 m2/g) (2,6-diphenyl-p-phenyleneoxide)
Tenax GR
(24 m2/g) (same as above with 30% graphite)
Porapak N
(300 m2/g) (Divinylbenzene w/copolymer ethylene glycol
dimethylacrylate)
Chromosorb 106
(750 m2/g) (Cross-linked polystyrene)
HayeSep D
(795 m2/g) (High purity divinylbenzene)
Granular
Designed to retain and release mid to large molecular weight compounds
Max. desorption temp. range from 220° to 350°C
Other Adsorbents
Glass Beads
5 m2/g
Silica Gel-15
750 m2/g
Petroleum Charcoal
1050 m2/g
Coconut Charcoal
1070 m2/g
Granular
Max. desorption temp. range 180° - 220°C
A Tool for Selecting an
Adsorbent(s) for Thermal
Desorption Applications
The two goals of this study
To demonstrate the relative difference between the most
commonly used adsorbents in the field of Thermal
Desorption.
To provide Thermal Desorption users a simple tool in
choosing the right adsorbent(s) for their applications
Scope of the research
Adsorbents:
• 24 different adsorbents were tested
Test Probe:
• 43-compound gas mix
Sample volume:
• Adsorbents were challenged with 6 diff. sample volumes
Analytical Tests:
• Thermal desorption and GC/MS
The packed adsorbent tubes
Glass Frit
Inlet of the tube
(0.5cc3 volume)
Adsorbent occupied
a 3.7cm bed-length
Glass wool plug & SS clip
Flow direction during the Challenge
Flow direction during Desorption
Gas Mix
Halocarbon 12
Chloromethane
Halocarbon 114
Vinyl chloride
1-3 Butadiene
Bromomethane
Ethyl Chloride
Halocarbon 11
Acrylonitrile
1,1-Dichloroethylene
Methylene chloride
3-Chloropropylene
Halocarbon 113
1,1-Dichloroethane
cis-1,2-Dichloroethane
Chloroform
1,2-Dichloroethane
1,1,1-Trichloroethane
Benzene
Carbon tetrachloride
1,2-Dichloropropane
Trichloroethylene
cis-1,3-Dichloropropene
trans-1,3Dichloropropene
1,1,2-Trichloroethane
Toluene
1,2-Dibromoethane
Tetrachloroethylene
Chlorobenzene
Ethylbenzene
m-Xylene
p-Xylene
Styrene
1,1,2,2-Tetrachloroethane
o-Xylene
4-Ethyltoluene
1,3,5-Trimethylbenzene
1,2,4-Trimethylbenzene
1,3-Dichlorobenzene
1,4-Dichlorobenzene
1,2-Dichlorobenzene
1,2,4-Trichlorobenzene
Hexchloro-1, 3-butadiene
Characteristics of the Gas Mix
Concentration : 1ppm of each compound
compound range: 50 to 260 in molecular weight,
-30 to 215°C in boiling point.
Spiking the tubes with the gas mix
• 20 mL of the gas mix
• Injected into a stream of N2
• N2 carried the compounds to the tube
Challenge volume (N2)
1
0.2
Liters
5
Liters
10
Liters
20
100
Liters
Liters
Liters
Parameters
The flow rate remained constant at 0.05 Liters/minute
Nitrogen (dry) served as the carrier gas
Nitrogen carries (pushes) the compounds
Gas Mix in the Syringe
.….
. . ..
………
………
….
Nitrogen Gas Flow
Adsorbent
Gas Mix injected
After 0.2 Liters
0 Liters
After 100 Liters
After 5 Liters
(Simulates an air
sample)
---- Small M.W. Chloromethane
---- Mid M.W. Benzene
---- High M.W. Dichlorobenzene
We analyzed “What remained on the adsorbent”
Thermally desorbing the adsorbents
Each adsorbents was
thermally desorbed to
determine the recovery of
each compound in the test
mix.
GERSTEL TDSA
Followed by a second
desorption of the same
adsorbent to determine if any
carryover was observed.
Calculating the recovery
• We spiked the same volume (20ml) of the gas mix onto a
Carbotrap-300 multi-bed tube. The gas mix was carried onto the
tube at 0.2 Liters.
• The response of each compound from the multi-bed tube was
assumed as 100% recovered. (The average of six analyses)
Carbotrap-300 multi-bed tube
1. bed:
2. bed:
3. bed:
Carbopack C Carbopack B Carbosieve SIII
Carbopack-C
Carbopack-B
Carbosieve-SIII
Chromatogram of the calibration on Carbotrap-300
CO2
Chromatographic view of the Carbopack(s)
0.2 Liter Volume
Terms defined
Relative Recovery
• The recovery of each compound, relative to the response of the same compound
thermally desorbed from a multi-bed adsorbent tube.
Challenge Volume
• The volume of nitrogen used to challenge the adsorbent. Simulates different air
sample volumes.
Breakthrough
• The compound traveled through the adsorbent without being retained.
Too Strongly Adsorbed
• The adsorbent retains the compound so strong that it’s not efficiently released
during thermal desorption. (Partial Desorption)
Irreversible Adsorption
• The adsorbent retains the compound, but it’s not released during thermal
desorption.
The outcome of this research …
How to use the performance charts
Information about the adsorbent
The 6 volumes studied
Green = Recommend for use
Recoveries are greater then 80%
Yellow = Use caution
(Watch the trend)
Too
strongly
adsorbed
Recoveries are 21 to 79%
Red = Not recommend
Recoveries are below 20%
Using the charts to design a multi-bed tube
Observe the trend
First Bed
Second Bed
Third Bed
Retained by the
Carbopack-X
These compounds are
retained
by the Carbopack-B
Sampling Direction
Example of how the charts can used:
You want to sample 10-Liters of an atmosphere containing:
•
•
•
•
Vinyl chloride
Methylene chloride
Toluene
1,2,4-Trichlorobenzene
•
“Since there is no single adsorbent that will trap & release all
four of these compounds, two adsorbents are needed. The
two adsorbents can be used to create a multi-bed tube.”
Solution: “You need a multi-bed adsorbent tube”
“Inlet” First adsorbent bed
Breaks through
Retained
Back-up adsorbent bed
Retained
Carryover was observed (Too Strongly Adsorbed)
Most likely irreversibly adsorbed
Should have a weaker adsorbent
placed in front
Testing different Carbon adsorbents?
•E.g. for air sampling
•Other applications
Carbon Adsorbent Sampler Kits
Supelco Literature
Bulletins and Application Notes
Supelco-Catalog
Air Methods Guide (2. Edition)
• Method references for solvent desorption tubes for more than
1000 compounds
Supelco Air Methods Guide (2nd Ed.)
Content:
• Compound (alphabetically)
– Name and/or category (e.g. VOC)
• Reference method (NIOSH, OSHA, EPA
and ASTM methods)
• Sample volume and flow rate
• Description of sampling media with catalog
number
• Analytical technique
Supelco Air Methods Guide - Example
Compound
Method
Volume
Liters
Rate
Liters/Min
Acenaphthene
NIOSH 5506
200-1000
2
Acenaphthene
NIOSH 5515
200-1000
2
Acenaphthylene
NIOSH 5506
200-1000
2
Acenaphthylene
NIOSH 5515
200-1000
2
Acetaldehyde
Acetaldehyde
Acetaldehyde
Acetaldehyde
Acetic Acid
Acetic Acid
NIOSH 2538
NIOSH 2539
NIOSH 3507
OSHA 68
NIOSH 1603
US Army
1-12
5
6-60
3
20-300
10-25
0.01-0.05
0.01-0.05
0.1-0.5
0.05
0.01-0.1
Acetic Anhydride
NIOSH 3506
25-100
0.2-1
Medium and/or Sample
Collection Device
Supelco
Model No.
Supelco
Cat. No.
SKC
Equiv
Analytical
Technique
XAD-2
PTFE filter
XAD-2
PTFE filter
XAD-2
PTFE filter
XAD-2
PTFE filter
XAD-2 c/w 2-HMP
XAD-2 c/w 2 HMP
fritted bubbler
XAD-2 c/w 2-HMP
coconut charcoal
Chromosorb P c/w Na2CO3
ORBO-43
----ORBO-43
----ORBO-43
----ORBO-43
----ORBO-25
ORBO-23
----ORBO-25
ORBO-32S
ORBO-70
20258
23390-U
20258
23390-U
20258
23390-U
20258
23390-U
20357
20257-U
64835-U
20357
20267-U
20256-U
226-30-04
225-17-07
226-30-04
225-17-07
226-30-04
225-17-07
226-30-04
225-17-07
226-27
226-118
225-36-2
226-27
226-01
NA
fritted bubbler
-----
64835-U
225-36-2
VIS
894
custom
225-9010
GC-NPD
821
custom
225-9009
GC-NPD
ORBO-32S
Carbotrap 349
20267-U
20243
226-01
NA
GC-FID
TD-GC/MS
ORBO-91
20360
226-121
GC-FID
ORBO-1101
ORBO-32L
ORBO-32S
20061
20228
20267-U
226-59-09
226-09
226-01
GC-NPD
GC-FID
GC-FID
HPLC-UV/Fl
GC-FID
HPLC-UV/Fl
GC-FID
GC-FID
GC-FID
HPLC-UV
GC-NPD
GC-FID
GC-FID
Acetic Anhydride
OSHA 102
7.5
0.05-0.5
Acetic Anhydride
OSHA 82
0.75
0.05
Acetone
Acetone
NIOSH 1300
NIOSH 2549
0.50-3
1-6
0.01-0.2
0.01-0.05
Acetone
OSHA 69
3
0.05
Acetone Cyanohydrin
Acetonitrile
Acetylene Dichloride
NIOSH 2506
NIOSH 1606
NIOSH 1003
0.30-12
1-25
0.2-5
0.2
0.01-0.2
0.01-0.2
glass fiber filter
c/w DMBA & DOP
glass fiber filter
c/w 1-2PP
coconut charcoal
3-bed thermal desorption tube
Carbosieve S-III
(Anasorb CMS)
Porapak QS
coconut charcoal
coconut charcoal
Acetylene Tetrabromide
NIOSH 2003
50-100
0.2-1
silica gel
ORBO-52S
20229
226-10
GC-FID
Acetylene Tetrachloride
NIOSH 1019
3-30
0.01-0.2
petroleum charcoal
ORBO-303
20040-U
226-38
GC-FID
Conclusion
This research provides thermal desorption users a tool in
choosing the right adsorbent(s) for their application.
In the future we plan to expand the list of compounds to
include:
• Polar
• sulfur compounds
• effect of humidity.
The direct link to the entire Technical Report:
http://www.sigmaaldrich.com/Graphics/Supelco/objects/11400/11342.pdf
Dziękuję za uwagę!
•Acknowledgement:
•Jamie Brown - Supelco, Bellefonte, USA

Selecting the most suitable adsorbent for Air - Sigma

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