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On-line chemical analysis of single aerosol particles
~ Pergamon
PIT: 80011-8502(96)00117-4»
J. A.,.• .JOI Sci., Vol 27, SuppL I, pp. 5289-5290,1996 Copyriaht 10 1996 ElJevier Sc:IeDce Ltd Prinledin Great BriIaiD.All riihu rnerved OO21-8S02/96 515.00 + 0.00
On-line Chemical Analysis of Single Aerosol Particles M. WEISS, P ,J.T, VERHEIJEN, J.C.M , MARIJNISSEN,
B.
SCARLETT
Delft University of Technology, Faculty of Chemical Technology, Julianalaan 136, 2628 BL Delft, The Netherlands
KEYWORDS Laser mass spectrometry, aerosol beam, single particle analysis, soot INTRODUCTION At Delft University of Technology an instrument has been developed to chemically characterize single particles in an aerosol. Simultaneously, it measures the size of the particles. This type of combined analysis can, for example, be useful to determine the origin of a particle. The system is able to measure particles from 0.4 J..lm up to 10 um. INSTRUMENTATION The instrument (Figure 1) has been 1iOn proposed by Marijnissen et al. (1988). Aerosol particles are introduced into the vacuum chamber of a time of flight TOFtul>e mass spectrometer by a differentially pumped nozzle system (Kievit, 1995). Ion 1lI11C1or HeNllUI' : (conlInuOuI: ,e mW) With the aid of two, continuous HeNe Dichroicmlrrorx'" co_ laser beams the particles are detected : ............ BoamlPliltor and sized by measuring their speed in the vacuum chamber. A 5 mJ exExc:lmorla_ (pulald: 5 mJ /3 nl) cimer laser, triggered by the optical particle detection system, fires approximately 1.5 J..lS after detection, vaporizes the particles and ionizes the reF'igure 1: Schematic ,. . sU' lt l'ng fragments. The ions are then VIew 0 f t he Instrument analyzed in a TOF mass spectrometer. The optical particle detection system offers information on particle size simultaneously with the chemical composition from the mass spectrometer. The distance between the locations of determination of size and chemical composition is not more than 1 mm. It is therefore possible to look for correlations between size and chemical composition of particles. With the current setup, up to ten particles per second can be analyzed.
_1..
--
EXPERIMENTS AND RESULTS Experiments have been done with two types of elementary carbon, Norit SX 2, a powdered activated carbon, and Printex U, which is produced from a hexane flame. As can be seen from Figure 2, the two types can be discriminated by the presence or absence of the 23/24 and 27 peaks. The anthracene spectrum shows carbon clusters which are shifted by several a.m.u, from the n x 12 positions towards higher masses because of the presence of hydrogen in the clusters. 8289
5290
Abstracts of the 1996 European Aerosol Conference
36
Printex U
60
48
72
84
24
12
-. :j
23
.i iii c
27
Norit SX2 39
Ol
'iii
c
.2 23 39
o
20
40
Anthracene
60
80
100 120 mle (amu)
140
160
180
200
220
Figure 2: Mass spectra of elementary carbon in the form of Norit SX 2 and Printex U, compared with the polycyclic aromatic hydrocarbon Anthracene Another set of experiments which will be presented quantifies the reproducibility of the mass spectra as a function of the material under investigation, the laser power and the particle size. ACKNOWLEDGMENT The authors would like to thank the Netherlands Foundation for Chemical Research (SON) for supporting these investigations. Financial aid was provided by the Netherlands Organization for Scientific Research (NWO) and the Foundation for Technical Sciences (STW). REFERENCES Kievit, O. (1995). Development of a laser mass spectrometer for aerosols. Ph. D. thesis, Delft University of Technology, Delft, The Netherlands. Marijnissen, J., B. Scarlett, and P. Verheijen (1988). Proposed on-line aerosol analysis combining size determination, laser induced fragmentation and time-of-flight mass spectrometry. Journal of Aerosol Science 19, 1307-1310.
PIT: 80011-8502(96)00117-4»
J. A.,.• .JOI Sci., Vol 27, SuppL I, pp. 5289-5290,1996 Copyriaht 10 1996 ElJevier Sc:IeDce Ltd Prinledin Great BriIaiD.All riihu rnerved OO21-8S02/96 515.00 + 0.00
On-line Chemical Analysis of Single Aerosol Particles M. WEISS, P ,J.T, VERHEIJEN, J.C.M , MARIJNISSEN,
B.
SCARLETT
Delft University of Technology, Faculty of Chemical Technology, Julianalaan 136, 2628 BL Delft, The Netherlands
KEYWORDS Laser mass spectrometry, aerosol beam, single particle analysis, soot INTRODUCTION At Delft University of Technology an instrument has been developed to chemically characterize single particles in an aerosol. Simultaneously, it measures the size of the particles. This type of combined analysis can, for example, be useful to determine the origin of a particle. The system is able to measure particles from 0.4 J..lm up to 10 um. INSTRUMENTATION The instrument (Figure 1) has been 1iOn proposed by Marijnissen et al. (1988). Aerosol particles are introduced into the vacuum chamber of a time of flight TOFtul>e mass spectrometer by a differentially pumped nozzle system (Kievit, 1995). Ion 1lI11C1or HeNllUI' : (conlInuOuI: ,e mW) With the aid of two, continuous HeNe Dichroicmlrrorx'" co_ laser beams the particles are detected : ............ BoamlPliltor and sized by measuring their speed in the vacuum chamber. A 5 mJ exExc:lmorla_ (pulald: 5 mJ /3 nl) cimer laser, triggered by the optical particle detection system, fires approximately 1.5 J..lS after detection, vaporizes the particles and ionizes the reF'igure 1: Schematic ,. . sU' lt l'ng fragments. The ions are then VIew 0 f t he Instrument analyzed in a TOF mass spectrometer. The optical particle detection system offers information on particle size simultaneously with the chemical composition from the mass spectrometer. The distance between the locations of determination of size and chemical composition is not more than 1 mm. It is therefore possible to look for correlations between size and chemical composition of particles. With the current setup, up to ten particles per second can be analyzed.
_1..
--
EXPERIMENTS AND RESULTS Experiments have been done with two types of elementary carbon, Norit SX 2, a powdered activated carbon, and Printex U, which is produced from a hexane flame. As can be seen from Figure 2, the two types can be discriminated by the presence or absence of the 23/24 and 27 peaks. The anthracene spectrum shows carbon clusters which are shifted by several a.m.u, from the n x 12 positions towards higher masses because of the presence of hydrogen in the clusters. 8289
5290
Abstracts of the 1996 European Aerosol Conference
36
Printex U
60
48
72
84
24
12
-. :j
23
.i iii c
27
Norit SX2 39
Ol
'iii
c
.2 23 39
o
20
40
Anthracene
60
80
100 120 mle (amu)
140
160
180
200
220
Figure 2: Mass spectra of elementary carbon in the form of Norit SX 2 and Printex U, compared with the polycyclic aromatic hydrocarbon Anthracene Another set of experiments which will be presented quantifies the reproducibility of the mass spectra as a function of the material under investigation, the laser power and the particle size. ACKNOWLEDGMENT The authors would like to thank the Netherlands Foundation for Chemical Research (SON) for supporting these investigations. Financial aid was provided by the Netherlands Organization for Scientific Research (NWO) and the Foundation for Technical Sciences (STW). REFERENCES Kievit, O. (1995). Development of a laser mass spectrometer for aerosols. Ph. D. thesis, Delft University of Technology, Delft, The Netherlands. Marijnissen, J., B. Scarlett, and P. Verheijen (1988). Proposed on-line aerosol analysis combining size determination, laser induced fragmentation and time-of-flight mass spectrometry. Journal of Aerosol Science 19, 1307-1310.