Passive Air Sampling for Ozone by Solid Phase Microextraction
I-Su Lee and Shih-Wei Tsai
Institute of Environmental Health, College of Public Health, National Taiwan University, Taipei, [email protected]
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Outline
IntroductionPurposeMaterials and methodsResultsConclusions
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Introduction
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Ozone
One of the major air pollutants
Ground level is produced by reaction between NO2, organic gas and sunlight
Exposures might cause severe health effects
4Source, U.S. EPASource, U.S. EPA
Methods of Sampling and Analysis
Direct instrumentUV-light absorption…...
Personal samplerActivePassive
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Active VS. Passive
Active Passive
Advantage High accuracyShort term monitoring
LightHigh accuracyOperation easinessLong term monitoring
Disadvantage Need pumpHeavyNot reusable
Low sensitivity Sample storage hardNot reusable
6source, http://www.tva.gov/environment/air/ontheair/outdoor.htm
The advantages of SPME
Integration of sampling、extraction、concentration、sample injectionReduce and simplify the extraction proceduresSolvent-freeGood detection and quantitation limitReusable
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Purpose
Develop a passive sampler for ozone based on the technique of SPME
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Expected reaction
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N C C N N CO
HDPE
ozone+ other product
F
F
F
CH 2
FFO NH 2
N CO
H
F F
CH 2
FF
FO N C
H
NF F
F CH 2
FFO N C
H
N
PFBHA
+
+
Pyridin-4-aldehyde-PFBHA
Materials and methods
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Materials
1,2-Di-(4-pyridyl)ethylene(DPE)Pyridin-4-aldehydePFBHAOzoneOximeExposure systemSPME diffusion sampler
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Chromatogram of oxime
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CH2O N
FF
F
FFC
H
N
CH2O N
FF
F
FFC
H
N
Synthesize oxime
Aldehyde and PFBHA form
oxime on SPME
Reaction time between PFBHA and pyridin-4-aldehyde
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Materials
1,2-Di-(4-pyridyl)ethylene(DPE)Pyridin-4-aldehydePFBHAOzoneOximeExposure systemSPME diffusion sampler
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Exposure system
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Passive sampler
Hood
Mixing chamber
Exposure chamber
Continuous analyzer
Ozone generator
Materials
1,2-Di-(4-pyridyl)ethylene(DPE)Pyridin-4-aldehydePFBHAOzoneOximeExposure systemSPME diffusion sampler
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SPME diffusion sampler
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Perspective view of the passive sampler: (a) SPME fiber assembly,
(b) PTFE septum, (c) PTFE tubing, and (d) cap/PTFE tape.
Fiber selection
fiberarea
Oxime* DPE**
PDMS 455475 -
PDMS/DVB 1125855 8852208
CAR/PDMS nd -
CW/DVB 110338 -
DVB/CAR/PDMS 1168172 872430*pyridin-4-aldehyde extract 5min and PFBHA extract 2min,
GC inject port temperature 250 ºC, desorption time 2min**DPE extract 30min, GC inject port temperature 250 ºC, desorption time 5min
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Desorption efficiency of oxime
desorption time(min)#
areadessoption
efficiency*(%)first second
1 16671.055 797.887 95.43%
2 15390.997 468.4785 97.05%
5 15269.862 398.117 97.46%
7 14746.4935 0 100.00%
# aldehyde adsorption 1 min, PFBHA react 20min, temperature of GC inject port 270 ºC*first area/(first area + second area)
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Methods
Fiber PDMS/DVB
DPE loaded method Direct extraction 30sec
GC inject port temperature 270 ºC
Desorption time 7min
PFBHA reaction time 20min
GC temperature program 150 ºC 250 ºC(15min)
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10 ºC/min
Results
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Test on real sample
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Ozone concentration : 400ppbExpose 4hr
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Fick’s First Law : nf = Dg(A/Z) ∫Cg(t)dt
nf and Q is the sampling mass of the analyte
Sampling Rate = Dg(A/Z)
Dg : Binary diffusion coefficient of analyte in air, cm2min−1
A : Surface area of the needle opening, cm2
Z : Retracted fiber path length, cm
Fick’s First Law
Q=RCT*source: Jacek A.K. and Inman N.. Sampling and sample-preparation strategies based on solid-phase
microextraction for analysis of indoor air. Trends in Analytical Chemistry, 21 (12); 840-850 (2002)
Fiber condition
Coating DPE
React with
PFBHA
GC analyse
Fiber condition
Coating DPE
Coating PFBHA
GC analyse
method 1
method 2
sampling Wait 20min
sampling
Sampling method
ozone concentration × exposure time vs. oxime mass
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Pyridin-4-aldehyde storage
Day* Area
0 2998.857
1 2477.574
4 2160.433
*aldehyde adsorption 1min, storage in 4 ºC, PFBHA react 20min
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Compare with other samplerSampling reagent Instrument Detection limit
1,2-di(4-pyridyl)ethylene(DPE) GC-ECDMethod 1, 120 ppb-hrMethod 2, 30 ppb-hr
1,2-di(4-pyridyl)ethylene(DPE) Spectrophotometry(422nm) 3 ug/m3 for a one week exposure
indigo carmine Spectrophotometry(408nm) 0.7 ppm-hr, 50 ppb for 8 hr
potassium iodideSpectrophotometry(575nm)
ion chromatography(IC)
3-methyl-2-benzothiazolinone acetone azine (MBTH ) Spectrophotometer(504nm) 0.09 ppm-hr,
4 ppb for 24 hr
p-acetamidophenol(p-ATP) Spectrofluorimeter
nitrite ion ion chromatography(IC)201 ppb-hr,
17 ppb for 12 hr, 8 ppb for 24 hr
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Conclusions
More sensitiveReusableSolvent-freeBackground noiseCoated fiber should be prepared before samplingInterferenceField test
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AcknowledgementNSC 95-2314-B-002-329, Taiwan
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