A Nano-size Particle Sampler using a Differential Mobility ...
Transcript of A Nano-size Particle Sampler using a Differential Mobility ...
A Nano-size Particle Sampler using a Differential Mobility Analyzer 9th ETH Conference on Combustion generated Nanoparticles, 17, Aug. 2005
Ikegami-shincho
Toshihiko MYOJO, Mariko Ono-OgasawaraNational Institute of Industrial Health, Kawasaki, Japan
Contents
ObjectiveDifferential mobility analyzerPAH analysis using direct injection GC-MSField samplingResults
Objective
Differential mobility analyzer (DMA) extracts aerosol particles ranging from 1 to 1000 nm in diameter.It is advantageous that DMA can be operated at normal pressure condition, because volatile or semi-volatile PAHs are unstable at low pressure.We tested twin custom-made DMAs as nano-particle samplers.DMA sampling flow-rate was increased up to 4 l/min to increase sample mass.
Contents
ObjectiveDifferential mobility analyzerPAH analysis using direct injection GC-MSField samplingResults
Specification of DMA
r1
r2L
Sheath flow
Aerosol flow
Monodisperse aerosol
Excess flow
DC high volt
Ground
Teflon
Stainless steel
Aerosol inlet
Aerosol outlet
Slit width
Filter positionfor visualization
Teflon
Qa
Qc
Qc
Q s
Electrode lengthL: 40 cm
Electrode radiusr1: 2.5 cmr2:1.5 cm
Applied voltageV: 0 – 10000 V
Sheath flow rateQc: 3 – 30 L/min
Size classification theory of DMA
Electrical mobility of particle; Zp
Zp = peCm/(3πµdp) (1)
dp: diameter, p :number of charge, e :elementarycharge, µ :viscosity, Cm: Cunningham’s correction factor
Size classification theory of DMA (cont.)
Electrical mobility of particle extracted through DMA slit; Zpc
Zpc={Qc+(1/2)(Qa-Qs)}ln(r1/r2)/(2πVL) (2)
Width of the mobility spread; ∆Zp
∆Zp =(Qa+Qs)ln(r1/r2)/(2πVL) (3)
Aerosol concentration at DMA outlet
Qa/Qc=0.33
Qa/Qc=0.1
Zp
2∆Zp
ni
dp
N/d
ln(d
p) Aerosol IN
DMA
Aerosol OUT∆no = ni∆Zp
Aerosol concentration of the size at Zpc; ni
Aerosol concentration extracted through DMA slit; ∆no
Aerosol concentration at DMA outlet
Aerosol concentration extracted through DMA slit; ∆noAerosol concentration of the size at Zpc; ni
∆no = ni ∆Zp (4)
If Qa = Qs, then ∆Zp = (2Qa/Qc) Zpc∆no = ni (2Qa/Qc) Zpc (5)
Collected particles =Qa ni (2Qa/Qc) Zpc (6)for unit time
Ambient aerosol concentration at DMA outlet
0.10
20
40
60
80
100
0.05 0.2
Ambient aerosol 40cm DMA
Concentration (p/cm3 )
Diameter (µm)
Aerosol flow 2 Lpm 0.6 Lpm
Size distribution of outlet aerosol from DMA(sequentially measured by SMPS)
0.01 0.1 1
0.08 µm 40cm DMA6-0.6 L/min
Diameter (µm)0.01 0.1 1
0.24 µm
0.08 µm40cm DMA6-2 L/min
dN/d log(dp)
Diameter (µm)
Size distribution of outlet aerosol from DMA(sequentially measured by SMPS)
10 100
0
50000
100000
150000
200000
240 nm (L-2)
150 nm (L-3)
80 nm (L-4)
50 nm
40cmDMA -> SMPSQc 12Lpm, Qa 4LpmIncense smoke
dN/dlog(dp)
D iameter (nm)
Contents
ObjectiveDifferential mobility analyzerPAH analysis using direct injection GC-MSField samplingResults
PAH analysis using direct injection GC-MSPhenanthrene PHEAnthracene ANTFluoranthene FLUPyrene PYRBenzo(a)anthracene BaAChrysene CHRBenzo(b)fluorantheneBenzo(k)fluoranthene
BbkF
Benzo(e)pyrene BePBenzo(a)pyrene BaPIndeno(1,2,3-cd)pyrene INDDibenzo(a,h)anthracene DBahABenzo(ghi)perylene BghiP
GC conditions
Instruments: Thermoquest TraceGCQColumn: SGE HT8, 30 m x 0.25 mm i.d.,
Film thickness: 0.25mmCarrier Gas : He 1mL/minTemp Condition: 80ºC (1 min, hold)
15ºC/min to 350ºC (9 min)Inj. Temp: 300ºC, Splitless Injection
MS conditions
Ion Source Temp: 225ºC Transfer Line Temp: 300ºCMS Mode: Selected Ion Monitoring (SIM Mode)Standard Sample:
NIST Standard Reference Material 1649(Ambient Particulate Matter)
PAH concentration was determined by comparison of peak area of the standard sample and collected sample.
0 5 10 15 20 25Time (min)
0
50
1000
50
1000
50
1000
50
100
Rel
ativ
e A
bund
ance 0
50
100
11.4012.1510.738.215.004.25
13.50 13.88
12.64 14.31
16.00
14.97 16.99
17.7918.22
18.4317.53
20.31
19.9419.71 20.90 22.52 2
FluoranthenePyrene
Benzo(a)anthracene
Benzo(b+k)fluorantheneBenzo(e)pyrene
Indeno(1,2,3-cd)pyrene
MW=202
MW=228
MW=252
MW=276
MW=178Phenanthrene Anthracene
Chrysene
Benzo(ghi)perylene
Chromatograms (NIST SRM1649)
Benzo(a)pyrene
Dibenzo(a,h)anthracene
Calibration curves (NIST SRM1649)
R2 = 0.9297
R2 = 0.9747
R2 = 0.9406
R2 = 0.9637
R2 = 0.95990
1000000
2000000
3000000
4000000
5000000
6000000
0 0.01 0.02 0.03 0.04
Sample amount (µg)
Are
a
PHEPYRCHRBaPBgP
Contents
ObjectiveDifferential mobility analyzerPAH analysis using direct injection GC-MSField samplingResults
Ikegami-shincho, Kawasaki, Japan
DMA 1240 nm
DMA 280 nm
Filter holderCyclone
Roadside Air monitering station
Road side at Ikegami-shincho, Kawasaki, Japan
Sampling conditions
Date: 2005, Jan. 24 – Jan. 28 Sampling flow rate;Whole: 2 L/minDMA 1 and 2: 4 L/minDMA sheath flow rate: 12L/minDMA 1: 1025 V, DMA 2: 6090 VFilter: Whatman QM-A micro quartz fibre filter
Contents
ObjectiveDifferential mobility analyzerPAH analysis using direct injection GC-MSField samplingResults
Particles deposited on DMA electrodes
240 nm
100 nm pore
80 nm
PAHs concentration and their ratio
0
5
10
15
20
25
Whole-w1240 nm-w180 nm-w1
PAH
(ng/
m3)
0%
20%
40%
60%
80%
100%
Whole-w1240 nm-w180 nm-w1
BghiP
DBahA
IND
BaP
BeP
BbkF
CHR
BaA
PYR
FLU
ANT
PHE
PAHs concentration and their ratio
0
1
2
3
4
5
PHEANT
FLU
PYR
BaACHRBbkFBeP
BaP
INDDBahABghiP
0.0
0.1
0.2
0.3
0.4
0.5
PHE
ANT
FLU
PYR
BaACHRBbkFBeP
BaP
INDDBahABghiP
0.0
0.1
0.2
0.3
0.4
0.5
PHEANT
FLU
PYR
BaACHRBbkFBeP
BaP
INDDBahABghiP
ng/m3
80 nm 240 nm whole
Sampled ambient particles on each filter at Ikegami-shincho
DateWhole DMA
240 nm 80 nm2005/Jan/24
/
2005/Jan/28
Collected particle mass* (µg)600 50 30Whole PAH **(ng)239 51.8 22.9 BaP (ng)12.9 3.8 1.5Sampling volume (m3)11.2 21.8 22.4
*: Sensitivity of balance =10 µg**: Sensitivity of PAH analysis = 0.1 ng
Summary
DMA can be used as a nanoparticle sampler.To increase flow ratio of aerosol flow and sheath flow of DMA means to increase particle amount through DMA slit.Four days sampling by this sampler at road side collected enough amount of nanoparticles for chemical analysis of PAHs.If we can increase DMA sheath flow-rate, we can increase sampling flow rate more than 4 l/min.
AcknowledgementsThe authors deeply appreciate to Dr. S. Kobayashi, National Institute of Environmental Studies, for his arrangement of their air monitoring station at Ikegami-shincho, Kawasaki, Japan.This work was supported by grants of EPA, Japan and the Smoking Research Foundation.
Thank you for your attention !