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 !