EP1274117A2 - Method and apparatus for the analysis of the chemical composition of aerosol particles - Google Patents

Abstract

Detecting the chemical composition of aerosol particles involves introducing an aerosol, particle or gas stream (18) into an ion source of a mass spectrometer, in which the aerosol or particle stream hits a heatable surface in the ionization region of the ion source; heating the heatable surface to a pre-selected temperature; and detecting ions formed directly on the heatable surface in the mass spectrometer. Detecting the chemical composition of aerosol particles involves introducing an aerosol, particle or gas stream (18) into an ion source of a mass spectrometer vertical to the direction of the ions to be detected, in which the aerosol or particle stream hits a heatable surface (10) in the ionization region of the ion source; heating the heatable surface to a pre-selected temperature; and detecting ions formed directly on the heatable surface in the mass spectrometer or ionizing the substances vaporized by the aerosol particles or particles and detecting the ions in the spectrometer. An Independent claim is also included for a device for carrying out the above process. Preferred Features: The heatable surface is brought to a low temperature to enrich the aerosol particles or particles. Ionization is carried out using resonance enhanced multiphoton ionization single photon ionization with VUV light or electron collision ionization. The heatable surface is a strip or wire.

Description

The invention relates to a method and an apparatus for quantitative determination of the chemical composition of aerosol particles.

In addition to parameters such as particle size distribution and particle concentration is the chemical composition of the particles particularly important since presumably properties like chemical reactivity and biological effectiveness associated with it are. Furthermore, especially on the surface adsorbed compounds discussed as an important factor, for the effect of aerosols on human health can be responsible.

Methods for determining the chemical composition of aerosol particles are based on online methods such. B. on laser mass spectrometry. However, no quantifiable statements can be made with these methods. Quantifiable analysis methods are only available off-line, ie the chemical composition can only be determined quantitatively from a collected sample.
Another elegant way of quantifying the chemical composition is the thermal evaporation of particles and particle components. The components are evaporated and ionized quantitatively by rapid heating of the particles to a certain preselected temperature and can thus be analyzed in a mass spectrometer.

Determination of the chemical composition of aerosol particles is carried out on collected samples using various analysis methods. These include extraction and separation of organic components by gas chromatography [1] or the determination of the elementary composition by means of PIXE [2]. However, the disadvantage of these methods is that they are off-line Character, because particle samples for long periods of time must be collected. But have such filter samples the disadvantage that during the analysis no statements about the Size distribution and possible distribution of the chemical components the particles hit over the measured size range can be. But important insights are straight about the morphology and the composition of individual or accessible to a few particles. Off-line one-particle analysis is, for example, with laser microprobe mass spectrometry possible [2, 3]. It allows the chemical Characterization of individual particles. The disadvantage is, however here too the off-line nature of the method, as with the Filter methods first collect particles and bring them for analysis Need to become. The problem here is that in the course of Time between sample sampling and analysis on which The surface of the particles adsorbed compounds evaporate and thus get lost for a possible proof. Chemical conversions within the particle are also possible, that occur during sample storage or transportation can.

In the literature, working on the basis of mass spectrometry Analyzers known the chemical composition allow for aerosol particles, with on-line analytics individual particles is possible [4, 5]. The aerosol particles are carried from the atmospheric state by means of a special inlet system into the vacuum of a mass spectrometer transferred. The chemical analysis takes place after the Size determination (using a light barrier technology - more aerodynamic Diameter) according to the principle of laser micro-sample mass spectrometry (Ionization with intensely focused Laser pulses of suitable wavelengths for element determination or for the detection of fragments of organic species).

One-particle laser mass spectrometry has been used in recent years successful for a number of studies on environmental aerosols or used on particles generated in the laboratory.

However, one-particle analysis of this kind only allows qualitative statements about the composition of the particles, because here the relatively low sensitivity and the strong Matrix effects are to be noted as clear disadvantages. Farther the received signal intensity is not in one linear relationship with the absolute amount of available Species.

A method of quantifying the chemical composition of particles based on mass spectrometric methods on the thermal evaporation of aerosols on a heated Area and subsequent ionization of the molecular cloud formed using laser radiation [6]. By using a Quadrupole mass spectrometers are only proof a single mass and therefore molecular species per unit of time possible.

If using a time-of-flight mass spectrometer would be the detection of all ions formed per unit time is possible, with a quantitative determination of all particle components becomes possible.

The object of the invention is an apparatus and a method for quantitative on-line determination of the chemical composition of aerosol particles.

This object is achieved by the features of the claims 1 and 11. The subclaims describe advantageous refinements the invention.

The measuring principle is based on the thermal evaporation of the particles on a heated surface and detection of the directly formed ions or ionization and subsequent detection of the gaseous molecules and molecular fragments formed using various ionization techniques. These include laser ionization with different wavelengths (266nm for REMPI - r esonance e nhanced m ulti p hoton i onisation, 118nm for V acuum- UV s ingle p hoton i onisation - VUV-SPI) as well as light-induced electron impact ionisation (LEI) [7, 8] ,

Time-of-flight mass spectrometry (TOFMS) is particularly suitable for fast (to maintain online capability) and complete (to detect all ions formed) analysis. The heated surface must be introduced into the ionization chamber in such a way that the fields required to accelerate the ions formed are disturbed as little as possible. This can be accomplished through the special geometric design and arrangement of this surface. First of all, spatially small areas are suitable, such as the flattened tip of a thin needle. With a TOF mass spectrometer, the particles are now analyzed by detecting the ions formed. In addition to the aerodynamic diameter of the particles, their chemical composition is also determined quantitatively.
The invention is explained in more detail below on the basis of exemplary embodiments with the aid of FIGS. 1 to 4.

die Fig. 1 eine schematische Darstellung der Gesamtapparatur

die Fig. 2 verschiedene Typen von beheizbaren Oberflächen sowie deren geometrische Anordnungsmöglichkeiten

die Fig. 3 beispielhafte Ausführungen der heizbaren Ionisationsfinger

die Fig. 4 Chopper-Vorrichtungen zur Größenselektion.

It shows

1 is a schematic representation of the overall apparatus

2 different types of heatable surfaces and their geometrical arrangement options

3 shows exemplary designs of the heatable ionization fingers

4 Chopper devices for size selection.

FIG. 1 shows a typical bipolar aeroreol time-of-flight mass spectrometer. In the inlet system 12, the particles are suddenly separated from the gas phase by a skimmer system with differential vacuum pump stages and accelerated as a function of their mass and thus coupled size. A particle beam 18 is formed. Only particles of a certain size fraction which can pass through a system of two time-coupled choppers 37 enter the ionization region (FIG. 4a). In this case, only those particles can penetrate freely into the ionization chamber that have a speed that matches the rotational frequency of the choppers. When using 3 choppers 37 (FIG. 4b), the increased requirements make the size range narrower, that is, the fractionation is finer.
The speed of the aerosol particles determined in this way can then be used, when the chopper position and circulation frequency are known, which can be determined and regulated via a light barrier system (not shown in the drawing for reasons of space), for calculating the flight time until it hits the heated baffle surface 1. This is necessary for triggering the ionization laser 17 and for triggering the pulsed ion extraction in the mass spectrometer. When they hit the heated surface, the components of the aerosol particle are thermally evaporated and ionized. The ions formed directly during evaporation and the components of the molecular cloud formed which have been subsequently ionized with a suitable wavelength of laser radiation are then detected by mass spectrometry.

2 a to g show possible geometric designs of the heatable area shown.

The use of spatially in the withdrawal direction of the ions As little as possible extended ionization fingers is necessary around the electric fields that lead to the withdrawal of the ions formed from the ion source are required to impair as little as possible. These heated elements 22, 23, 24, 25, 26, 28 are collinear to the aerosol jet, so that the Particles on the baffle 1 incident. Geometric possibilities for shaping the Ionization fingers are, for example, a pointed needle 22, a wire-shaped body 23 with a flattened impact surface 1 or a tapered body 24 with a flattened baffle 1. Slight deviations in the focus of the aerosol jet 18 can, for example, by enlarging the Baffle surface 1 must be compensated. This can be largely without influencing the electric fields in the ion source by shaping the baffle as an elongated rectangular Baffle 1 can be reached. Here comes as a body a suitably arranged plate-shaped body 25 in question. The heating of the elements 22, 23, 24, 25 can for example through thermal conduction (i.e. through contact with a body brought to temperatures of 30-2800 ° C) or by irradiating target region 1 with IR laser light respectively. Furthermore, the stretched baffle by a heating tape 26, which is heated via the contact wires 27 will be formed. The one formed by the heating tape 26 Area can also be pulsed briefly to the desired one Temperature can be brought up to one on the colder surface collected amount of particles (or their thermally evaporable Portion) to evaporate quantitatively and as described ionize and analyze.

One possibility for the improved heating of the stretched Impact surface by IR laser radiation is geometrical Formed as a wire-shaped body with a t-shaped Target region 28. Due to the constriction at the transition between Baffle 1 and wire can transfer heat from the area the area can be reduced, creating this geometry is especially suitable for use with IR laser pulses.

A possible version of an ionization finger is shown in FIG 3a. Here, a wire-shaped object 29 is made by contact with a heating element 32 to the desired temperature brought. For insulation, it is surrounded by ceramic sleeves 30, the surfaces of which are covered with a thin layer of metal, which can be connected to potential via a wire feed. Furthermore, the heating of the target region 1, as in Figure 3b shown, done only in a thin layer. For this is the baffle 1 as a thin high-resistance plate or Coating 33 executed, which with electrical leads 34 and leads 35, which is connected by a thin insulator layer 36 are separated.

Another option for ionizing the vaporized constituents is chemical ionization with a reactive gas (for example ammonia, NH ₃ ). This can be passed over the heated surface via a capillary inlet and react with the ions and molecules formed by impact on the impact surface 1 under the influence of electron bombardment (LEI). These chemically modified ionic components can then be detected in the TOFMS as described.

Instead of the skimmer system, a particle beam can be formed an alternate inlet can also be used to analyze fine and ultrafine particles. For this, the polydisperse aerosol first by means of an aerodynamic Focused lens [9] to a particle beam and then again through a system of 2 to 3 time-coupled choppers 37 selected a certain size fraction (FIG 4). Again, only those particles that have a have suitable speed and the correlated size pass freely through the rotating chopper 37 and hit the heated baffle 1. With this device can then be used in experiments with pulsed ion extraction the composition of fine particles can be determined. The The range of ultrafine particles (<150 nm) can, however, be the chopper system described no longer in different Size intervals are fractional because of the speed of the different particles in this size range almost becomes identical. A distinction between the different size fractions in this area, however, with an electrostatic Classifiers possible. This selects based on the Mobility in an electric field a certain size fraction from the polydisperse aerosol, these particles become then focused into a beam by the aerodynamic lens and aimed at the heated surface. A single one Chopper (Figure 4c) enables this again, for example Impact of defined quantities of particles on the surface. Becomes the area pulsed heated can also with this device ultrafine particles can be analyzed quantitatively. Because the number of molecules on the surface of fine and ultra-fine Molecules is very low is evidence of these molecules difficult to accomplish on individual particles. However, by collecting a certain amount you can Increase the amount of analyte molecules and enable detection. Through the sampling described, however Disadvantages of the conventional off-line methods avoided because the analysis takes place at almost the same time (on-line).

Double reflectron spectrometers can advantageously be used for the detection be used. These are suitable because of the possible simultaneous detection of both positive and negative ions very good for analysis of aerosol particles. The use of a double TOFMS system and pulsed Voltages to withdraw the ions ("delayed extraction" technique) thus allows great variability in the detection of chemical particle composition and particle properties.

1. Verwendung eines doppelten Reflektron TOFMS im bipolaren Mode (ein Flugrohr 19 für die negativen, ein Flugrohr 20 für die positiven Ionen), ständiger Beheizung der Fläche 1. und Nachionisationslaserpulsen 17. An den Blenden 2, 3, 4, 5 der Ionenquelle liegen bereits geeignete Potentiale an. Direkte Ionen, die durch thermische Ionisation gebildet werden, werden kontinuierlich abgezogen. Nach einem Ionisationslaserpuls 17 werden die photoionisierten oder durch Elektronenstoß ionisierten (LEI) positiven Molekülionen am TOFMS 20 nachgewiesen. Ständig direkt gebildete Ionen werden nur als Untergrundrauschen aufgenommen und sind somit unsichtbar.
Im TOFMS 20 werden somit nur Verbindungen, die verdampft wurden und über REMPI oder VUV ionisiert wurden nachgewiesen.

2. Verwendung eines doppelten Reflektron TOFMS im bipolaren Mode, ständiger Beheizung der Fläche 1 und Nachionisationslaserpulsen 17. Das Zentrum der Ionenquelle ist feldfrei während der thermischen Verdampfung auf der beheizten Fläche 1. Direkt gebildete positive und negative Ionen werden nicht beeinträchtigt. Nach dem Ionisieren der verdampften neutralen Moleküle mittels eines Ionisationslaserpulses mit geeigneter Wellenlänge 17, oder mit Elektronenstoßionisation (LEI) werden die Blenden 2, 3, 4, 5 der Ionenquelle schlagartig auf Hochspannung gelegt. Das TOFMS wird im bipolaren Modus betrieben (ein Flugrohr 19 für die negativen Ionen, ein Flugrohr 20 für die positiven Ionen). Die direkt gebildeten positiven Ionen und die durch Photoionisation oder Elektronenstoß gebildeten positiven Ionen werden im TORFMS 20 nachgewiesen, die direkt gebildeten negativen Ionen im TOFMS 19.

3. Verwendung eines doppelten Reflektron TOFMS, ständig beheizter Fläche 1 und chemischer Ionisation durch ein Reaktivgas induziert durch Elektronenstoß (LEI). An den Blenden 2, 3, 4, 5 der Ionenquelle liegen bereits geeignete Potentiale an. Direkte Ionen, die durch thermische Ionisation gebildet werden, werden kontinuierlich abgezogen. Durch Laserpulse ausgelöste Elektronen induzieren die chemische Ionisation durch Reaktion mit dem eingeleiteten Gas. Das TOFMS wird im bipolaren Modus betrieben (ein Flugrohr 19 für die negativen Ionen, ein Flugrohr 20 für die positiven Ionen). Die durch chemische Ionisation gebildeten positiven Ionen werden im TOFMS 20 nachgewiesen. Ständig direkt gebildete Ionen werden nur als Untergrundrauschen aufgenommen und sind somit unsichtbar.

4. Verwendung eines doppelten Reflektron TOFMS, ständig beheizter Fläche 1 und chemische Ionisation durch ein Reaktivgas induziert durch Elektronenstoß (LEI). Das Zentrum der Ionenquelle ist feldfrei während der Verdampfung auf der beheizten Fläche. Eventuell direkt durch thermische Ionisation gebildete Ionen werden nicht beeinflusst. Durch Laserpulse ausgelöste Elektronen induzieren die chemische Ionisation durch Reaktion mit dem eingeleiteten Gas. Danach werden die Blenden 2, 3, 4, 5 schlagartig auf Hochspannung gelegt. Das TOFMS wird im bipolaren Modus betrieben (ein Flugrohr 19 für die negativen Ionen, ein Flugrohr 20 für die positiven Ionen). Die durch chemische Ionisation gebildeten positiven Ionen sowie die direkt gebildeten positiven Ionen werden im TOFMS 20 nachgewiesen, die direkt gebildeten negativen Ionen werden im TOFMS 19 nachgewiesen.

5. Verwendung eines doppelten Reflektron TOFMS und kurzzeitig gepulst beheizter Fläche. Das innere der Ionenquelle ist feldfrei während dem Auftreffen der Partikel auf die Prallfläche 1. Da die Temperatur zu Beginn noch niedrig ist, werden die Partikel auf der Fläche aufgesammelt. Durch einen Heizpuls werden schlagartig Partikel und Verbindungen von der Oberfläche der Partikel verdampft und thermisch ionisiert. Danach wird schlagartig an die Blenden 2, 3, 4, 5 Hochspannung angelegt. Die direkt durch thermische Ionisation gebildeten positiven Ionen werden im TOFMS 20 nachgewiesen, die direkt gebildeten negativen Ionen werden im TOFMS 19 nachgewiesen.

6. Verwendung eines doppelte Reflektron TOFMS mit gepulster Beheizung der Prallfläche und Nachionisationslaserstrahlen. An den Blenden 4, 5 liegt zu Beginn schon eine geeignete Spannung an. Nach dem kurzzeitigen Aufheizen der Fläche direkt gebildete positive Ionen werden im TOFMS 20 nachgewiesen. Direkt gebildete negative Ionen werden zwar durch die Blenden 2, 3 abgezogen, aber z. B. durch ein Deflektionsfeld durch die Ablenkeinheit'9 so abgelenkt, dass sie den Detektor 13 des TOFMS 19 nicht erreichen. Vor dem Nachionisationslaserpuls 17 werden die Spannungen der Blenden 2, 3 auf geeignete Hochspannungen gelegt um im TOFMS 19 positive Ionen aus der Ionenquelle abzuziehen (die direkten Ionen haben bereits die Ionenquelle verlassen und sind im feldfreien Driftraum des TOFMS 20). Gleichzeitig wird das Deflektionsfeld abgeschaltet. Die durch die Nachionisation mit einem Laserpuls oder Elektronenstoß gebildeten positiven Ionen werden im TOFMS 19 nachgewiesen. Gleichzeitig kann ein Deflektionsfeld im Bereich der Ionenquelle im TOFMS 20 an die Elektrode 8 gelegt werden um eventuell gebildete negative Ionen vom Detektor 14 im TOFMS 20 abzuhalten.
Im positiven MS des TOFMS 20 sind die direkt über thermische Ionisation gebildeten Ionen sichtbar.
Im positiven MS des TOFMS 19 sind die durch die Nachionisation gebildeten Ionen sichtbar.

Possible configurations of methods are presented below as examples. They refer to FIG. 1. It should be noted here that the ion-optical elements in FIG. 1 are not shown completely.

1. Use of a double reflectron TOFMS in bipolar mode (a flight tube 19 for the negative, a flight tube 20 for the positive ions), constant heating of the surface 1. and post-ionization laser pulses 17. Lie on the diaphragms 2, 3, 4, 5 of the ion source already suitable potential. Direct ions, which are formed by thermal ionization, are continuously extracted. After an ionization laser pulse 17, the photo-ionized or electron-impact ionized (LEI) positive molecular ions are detected on the TOFMS 20. Ions that are directly formed are only recorded as background noise and are therefore invisible.
In TOFMS 20, only compounds that have been evaporated and ionized via REMPI or VUV are detected.

2. Use of a double reflectron TOFMS in bipolar mode, constant heating of surface 1 and post-ionization laser pulses 17. The center of the ion source is field-free during thermal evaporation on the heated surface 1. Directly formed positive and negative ions are not affected. After ionizing the vaporized neutral molecules by means of an ionization laser pulse with a suitable wavelength 17, or with electron impact ionization (LEI), the diaphragms 2, 3, 4, 5 of the ion source are suddenly connected to high voltage. The TOFMS is operated in bipolar mode (a flight tube 19 for the negative ions, a flight tube 20 for the positive ions). The directly formed positive ions and the positive ions formed by photoionization or electron impact are detected in TORFMS 20, the directly formed negative ions in TOFMS 19.

3. Use of a double reflectron TOFMS, permanently heated surface 1 and chemical ionization by a reactive gas induced by electron impact (LEI). Suitable potentials are already present at apertures 2, 3, 4, 5 of the ion source. Direct ions, which are formed by thermal ionization, are continuously extracted. Electrons released by laser pulses induce chemical ionization by reaction with the introduced gas. The TOFMS is operated in bipolar mode (a flight tube 19 for the negative ions, a flight tube 20 for the positive ions). The positive ions formed by chemical ionization are detected in the TOFMS 20. Ions that are directly formed are only recorded as background noise and are therefore invisible.

4. Use of a double reflectron TOFMS, permanently heated surface 1 and chemical ionization by a reactive gas induced by electron impact (LEI). The center of the ion source is field-free during evaporation on the heated surface. Any ions formed directly by thermal ionization are not affected. Electrons released by laser pulses induce chemical ionization by reaction with the introduced gas. Then the apertures 2, 3, 4, 5 are suddenly placed on high voltage. The TOFMS is operated in bipolar mode (a flight tube 19 for the negative ions, a flight tube 20 for the positive ions). The positive ions formed by chemical ionization and the directly formed positive ions are detected in TOFMS 20, the directly formed negative ions are detected in TOFMS 19.

5. Use of a double reflectron TOFMS and a briefly pulsed heated surface. The inside of the ion source is field-free during the impact of the particles on the impact surface 1. Since the temperature is still low at the beginning, the particles are collected on the surface. With a heating pulse, particles and compounds are suddenly evaporated from the surface of the particles and thermally ionized. Then high voltage is suddenly applied to the apertures 2, 3, 4, 5. The positive ions formed directly by thermal ionization are detected in TOFMS 20, the directly formed negative ions are detected in TOFMS 19.

6. Use of a double reflectron TOFMS with pulsed heating of the impact surface and post-ionization laser beams. A suitable voltage is already present at the diaphragms 4, 5 at the beginning. After the surface has been briefly heated, positive ions formed directly are detected in the TOFMS 20. Directly formed negative ions are withdrawn through the apertures 2, 3, but z. B. deflected by a deflection field by the deflection unit 9 such that they do not reach the detector 13 of the TOFMS 19. Before the post-ionization laser pulse 17, the voltages of the apertures 2, 3 are applied to suitable high voltages in order to draw positive ions out of the ion source in the TOFMS 19 (the direct ions have already left the ion source and are in the field-free drift space of the TOFMS 20). At the same time, the deflection field is switched off. The positive ions formed by post-ionization with a laser pulse or electron impact are detected in TOFMS 19. At the same time, a deflection field in the area of the ion source in the TOFMS 20 can be applied to the electrode 8 in order to keep any negative ions that may be formed from the detector 14 in the TOFMS 20.
The ions formed directly via thermal ionization are visible in the positive MS of TOFMS 20.
The ions formed by the post-ionization are visible in the positive MS of TOFMS 19.

applications

a) Process analytics (e.g. combustion aerosols from industrial sources)
A large number of particles are created during combustion processes. These can have different chemical properties. In addition to the particle core, the loading of the particles with toxic organic compounds as a health-relevant parameter is also discussed. It is also necessary to know the exact amounts of chemical substances as precisely as possible in order to obtain defined statements about the effects on the environment and health.
A quantifiable on-line analysis of aerosol particles depending on the process parameters enables environmentally and health-friendly combustion conditions to be found (process-integrated environmental protection).

b) Monitoring of environmental aerosols
The environmental aerosol can be comprehensively characterized using the method according to the invention (aerodynamic diameter, quantitative chemical composition). This is interesting e.g. B. to record the exposure of the population to anthropogenic aerosols and their health effects.

c) Monitoring the production of defined nanoparticles
With the method according to the invention, artificially produced or produced aerosols can be comprehensively characterized (aerodynamic diameter, quantitative chemical composition). This is interesting for B. to optimize and monitor the production / process conditions.

Reference symbol list :

1

electronically controlled, individually pulsable Power supply for panels (2, 3, 4, 5), liners (6, 7), baffles (8, 9) and other ion-optical elements (not shown)

2

Second aperture from TOFMS 19

3

First aperture of TOFMS 19

4

First aperture of TOFMS 20

5

Second aperture of TOFMS 20

6

Liner from TOFMS 20

7

Liner from TOFMS 19

8th

Deflector plate from TOFMS 20

9

Baffle plate from TOFMS 19

10

heated object

11

Vacuum lock for heatable element

12

Inlet system with skimmers

13

TOFMS 19 detector

14

TOFMS 20 detector

15

vacuum pumps

16

pulsed laser beam for heating the impact surface 21 (generally IR light, e.g. 10.6 µm from CO ₂ laser)

17

pulsed laser beam for post ionization with REMPI or Single-photon ionization (generally UV or VUV, 0.1-30ns pulse width, 0.01-100000 µJ / pulse)

18

Aerosol particle beam

19

First TOFMS for negative (bipolar mode) or positive ions

20

Second TOFMS for positive ions

21

baffle

22

Acicular body

23

Wire-shaped body

24

Tapered body

25

Plate-shaped body

26

Heating tape or coil

27

contact wires

28

Wire-shaped body with a t-shaped target region

29

Tapered body

30

Metal-coated ceramic covers

31

contact wires

32

heating element

33

High-resistance plate

34

Electrical supply

35

Electrical discharge

36

insulation

37

chopper

Bibliography :

[1] Cass, GR, Organic molecular tracers for particulate air pollution sources, trends in analytical chemistry, 17 (6) , 356-366, 1998.

[2] K. Willeke, PA Baron (Ed.), Aerosol Measurement, Van Nostrand Reinhold, New York 1993.

[3] R. Zimmermann, L. Van Vaeck, A. Adams, M. Davidovic, M. Beckmann, Analysis of the organic adsorbate layer on sootparticies from an incineration plant by fourier transform laser microprobe mass spectrometry (FT-LMMS): Chemical fingerprints, Environmental Science and Technology, (submitted).

[4] SH Wood, KA Prather, Time-of-flight mass spectrometry methods for real time analysis of individual aerosol particulates, trends in analytical chemistry, 17 (6) , 346-356, 1998.

[5] A. Trimborn, K.-P. Hinz, B. Spengler, Online analysis of atmospheric particies with a transportable laser mass spectrometer, Aerosol Science and Technology, 33 (1-2) , 191-201, 2000.

[6] JT Jayne, DC Leard, X. Zhang, P. Davidovits, KA Smith, CE Kolb, DR Worsnop, Development of an aerosol mass spectrometer for size and composition analysis of submicron particles, Aerosol Science & Technology, 33 (1- 2) , 49-70, 2000.

[7] HJ Heger, R. Zimmermann, R. Dorfner, M. Beckmann, H. Griebel, A. Kettrup, U. Boesl, On-line emission analysis of polycyclic aromatic hydrocarbons down to pptv concentration levels in the flue gas of an incineration pilot plant with a mobile resonance-enhanced multiphoton ionization time-of-flight mass spectrometer, Analytical Chemistry, 71 , 46-57, 1999.

[8] F.Mühlberger, R.Zimmermann, A mobile mass spectrometer for comprehensive on-line analysis of trace and bulk components of complex gas mixtures , Analytical Chemistry (submitted).

[9] GA Petrucci, PB Farnsworth, P. Cavalli, N. Omenetto, A differentially pumped particie inlet for sampling of atmospheric aerosols into a time-of-flight mass spectrometer: Optical characterization of the particie beam, Aerosol Science and Technology, 33 (1-2), 105-121, 2000.

Claims (11)

Method for the detection of the chemical composition of aerosol particles with the following process steps: a) introducing an aerosol or particle beam or a gas jet into an ion source of a time-of-flight mass spectrometer perpendicular to the direction of flight of the ions to be detected, the aerosol or particle beam striking a heatable surface in the ionization region of the ion source. b) heating this heatable surface to a preselectable temperature c) Detection of the ions formed directly on the heatable surface in the time-of-flight mass spectrometer or ionization of the substances evaporated by the aerosol particles or particles and detection of the ions in the time-of-flight mass spectrometer. A method according to claim 1, characterized in that the heatable surface is brought to a low temperature for the enrichment of the aerosol particles or particles. Method according to claim 1 or 2, characterized in that the ionization takes place via resonance enhanced multiphoton ionization (REMPI). A method according to claim 1 or 2, characterized in that the ionization takes place via single photon ionization (SPI) with VUV light. A method according to claim 1 or 2, characterized in that the ionization takes place via electron impact ionization (EI). Method according to one of claims 1 or 2, characterized in that components from a gas, aerosol or particle beam is ionized directly via thermal ionization on the heated surface. Method according to one of claims 1 to 6, characterized in that the tip of a needle is used as the heatable surface, the needle being arranged collinear to the aerosol or particle beam. Method according to one of claims 1 to 6, characterized in that a belt is used as the heatable surface. Method according to one of claims 1 to 6, characterized in that a wire is used as the heatable surface. Method according to one of claims 1 to 9, characterized in that a certain particle size range is used for the measurement. Device for detecting the chemical composition of aerosol particles consisting of an ion source, a gas, aerosol or particle beam source which generates a directed beam, a time-of-flight mass spectrometer, ionization devices, characterized by a heatable surface with a holder in the trajectory of the directed beam in the region of the ionization region in the ion source of the time-of-flight mass spectrometer.

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