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US 5,681,752 AGranted
Method and apparatus for determining the size and chemical composition of aerosol particles
AssigneeThe Regents of the University of California
InventorKimberly A. Prather
Life of this patent
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Abstract
The invention provides an improved mass spectrometer apparatus, and related method, that characterizes aerosol particles, in real time, according not only to their chemical composition, but also to their size. This added information can be of critical importance when evaluating risks associated with aerosol particles of particular chemical composition. The apparatus achieves this beneficial result in a reliable fashion by first detecting the presence and size of individual aerosol particles moving along a predetermined particle path and by then directing a pulse of high-intensity light at the particle, to desorb and ionize the particle, for analysis of its chemical composition.
Claims39
Apparatus for determining the size and chemical composition of individual polydisperse aerosol particles, in real time comprising:
- a particle accelerator that directs a succession of individual polydisperse aerosol particles along a predetermined particle path;
- an optical detector, disposed along the particle path, that detects the speed of individual polydisperse aerosol particles traveling along the path and produces a corresponding timing signal for each detected particle, wherein the detected speed of each particle indicates the particle's aerodynamic size;
- a laser oriented to direct a beam of light across the particle path, separate from and downstream of the optical detector;
- a controller, responsive to each timing signal produced by the optical detector, that controls the laser to direct the beam of light across the particle path coincident with the arrival of each aerosol particle whose speed is detected by the optical detector, such that each particle is desorbed into its component molecules;
- and
- a mass spectrometer that determines the chemical composition of the component molecules associated with each desorbed particle.
3 more elements
Apparatus for determining the size and chemical composition of individual polydisperse aerosol particles, in real time, comprising:
- means for directing a succession of individual polydisperse aerosol particles along a predetermined particle path;
- means for detecting the location and size of individual polydisperse aerosol particles traveling along the particle path;
- laser means located separate from and downstream of the detecting means for directing a beam of light at the successive aerosol particles detected by the means for detecting after a suitable time delay to desorb each particle into its component molecules and to ionize at least a portion of such molecules;
- and
- mass spectrometer means for determining the chemical composition of the ionized molecules associated with each desorbed particle.
2 more elements
A method for determining the size and chemical composition of individual polydisperse aerosol particles, in real time, comprising:
- directing a succession of individual polydisperse aerosol particles along a predetermined particle path;
- detecting aerodynamic size of individual polydisperse aerosol particles traveling along the particle path at a detection location;
- directing a collimated beam of light at the successive aerosol particles detected in the element of detecting, at a location downstream of the detection location, and after a suitable time delay, to desorb each particle into its component molecules and to ionize at least a portion of such molecules;
- and
- determining the chemical composition of the ionized molecules associated with each desorbed particle.
2 more elements
Apparatus for determining the size and chemical composition of individual aerosol particles, in real time, comprising:
- a particle accelerator that directs a succession of individual aerosol particles along a predetermined particle path wherein the particle accelerator includes a multiple-stage vacuum system, each stage of the system including a vacuum pump and each stage directing individual aerosol particles along the particle path;
- an optical detector, disposed along the particle path, that detects the speed of individual aerosol particles traveling along the path, the detected speed of each particle indicating the particle's aerodynamic size;
- a laser oriented to direct a beam of light across the particle path, downstream of the optical detector;
- a controller that controls the laser to direct the beam of light across the particle path coincident with the arrival of individual aerosol particles, such that each particle is desorbed into its component molecules;
- and
- a mass spectrometer that determines the chemical composition of the component molecules associated with each desorbed particle;
- wherein the multiple-stage vacuum system includes a plurality of concentric tubes supporting a vacuum of progressively increasing amount, the plurality of concentric tubes being separated from each other by skimmers aligned along the particle path and being configured to be adjustably movable axially relative to each other, to vary the distances between the successive skimmers, along the particle path.
4 more elements
Apparatus for determining the size and chemical composition of individual aerosol particles, in real time, comprising:
- a particle accelerator that directs a succession of individual aerosol particles along a predetermined particle path;
- an optical detector, disposed along the particle path, that detects the speed of individual aerosol particles traveling along the path, the detected speed of each particle indicating the particle's aerodynamic size;
- a laser oriented to direct a beam of light across the particle path, downstream of the optical detector;
- a controller that controls the laser to direct the beam of light across the particle path coincident with the arrival of individual aerosol particles, such that each particle is desorbed into its component molecules;
- and
- a mass spectrometer that determines the chemical composition of the component molecules associated with each desorbed particle;
- wherein the optical detector includes
- a first light source that directs a first beam of light across the particle path, at a first predetermined location,
- a first detector that detects light scattered from the particle path due to impingement of the first beam of light on an aerosol particle traveling along the path,
- a second light source that directs a second beam of light across the particle path, at a second predetermined location, downstream of the first predetermined location,
- a second detector that detects light scattered from the particle path due to impingement of the second beam of light on an aerosol particle traveling along ht path, and
- a timing device for measuring the time delay between detection of scattered light by the first detector and detection of scattered light by the second detector, such time delay indicating the speed of the associated particle;
- and wherein the first and second light sources together include
- a laser that generates a laser beam having multiple wavelengths, and
- an optical assembly that separates the laser beam into the first and second beams of light, each having a wavelength different from the other, and that directs the first and second beams of light across the particle path, at the respective first and second predetermined locations.
12 more elements
Apparatus for determining the size and chemical composition of individual aerosol particles, in real time, comprising:
- a particle accelerator that directs a succession of individual aerosol particles along a predetermined particle path;
- an optical detector, disposed along the particle path, that detects the speed of individual aerosol particles traveling along the path, the detected speed of each particle indicating the particle's aerodynamic size;
- a laser oriented to direct a beam of light across the particle path, downstream of the optical detector;
- a controller that controls the laser to direct the beam of light across the particle path coincident with the arrival of individual aerosol particles, such that each particle is desorbed into its component molecules;
- and
- a mass spectrometer that determines the chemical composition of the component molecules associated with each desorbed particle;
- wherein the optical detector includes
- a first light source that directs a first beam of light across the particle path, at a first predetermined location,
- a first detector that detects light scattered from the particle path due to impingement of the first beam of light on an aerosol particle traveling along the path,
- a second light source that directs a second beam of light across the particle path, at a second predetermined location, downstream of the first predetermined location,
- a second detector that detects light scattered from the particle path due to impingement of the second beam of light on an aerosol particle traveling along the path, and
- a timing device for measuring the time delay between detection of scattered light by the first detector and detection of scattered light by the second detector, such time delay indicating the speed of the associated particle;
- and wherein the first and second light sources direct the respective first and second beams of light along paths that are substantially perpendicular to each other and that are in transverse planes that are substantially perpendicular to the particle path, such that aerosol particles are impinged on by both beams only if they travel along the center of the particle path.
10 more elements
Apparatus for determining the size and chemical composition of individual aerosol particles, in real time, comprising:
- means for directing a succession of individual aerosol particles along a predetermined particle path, wherein the means for directing includes a multiple-stage vacuum system, each stage of the system including a vacuum pump and each stage directing individual along the particles along the particle path;
- means for detecting the location and size of individual aerosol particles traveling along the particle path;
- laser means for directing a beam of light at the successive aerosol particles, to desorb each particle into its component molecules and to ionize at least a portion of such molecules;
- and
- mass spectrometer means for determining the chemical composition of the ionized molecules associated with each desorbed particle;
- wherein the multi-stage vacuum system includes a plurality of concentric tubes supporting a vacuum of progressively increasing among, such tubes being separated from each other by skimmers aligned along the particle path and being configured to be adjustably movable axially relative to each other, to vary the distances between the successive skimmers, along the particle path.
3 more elements
Apparatus for determining the size and chemical composition of individual aerosol particles, in real time, comprising:
- means for directing a succession of individual aerosol particles along a predetermined particle path;
- means for detecting the location and size of individual aerosol particles traveling along the particle path;
- laser means for directing a beam of light at the successive aerosol particles, to desorb each particle into its component molecules and to ionize at least a portion of such molecules;
- and
- mass spectrometer means for determining the chemical composition of the ionized molecules associated with each desorbed particle;
- wherein the means for detecting includes
- first detection means for directing a first beam of light across the particle path, at a first predetermined location, and for detecting light scattered from the particle path due to impingement of first beam of light on an aerosol particle traveling along the path,
- second detection means for directing a second beam of light across the particle path, at a second predetermined location, downstream of the first predetermined location, and for detecting light scattered from the particle path due to impingement of the second beam of light on an aerosol particle traveling along the path, and
- timing means for measuring the time delay between detection of scattered light by the first detection means and detection of scattered light by the second detection means, such time delay indicating the speed, and thus the aerodynamic size, of the associated particle;
- wherein the first and second detection means together include
- a laser that generates a laser beam having multiple wavelengths, and
- an optical assembly that separates the laser beam into the first and second beams of light, each having a wavelength different from the other, and that directs the first and second beams of light across the particle path, at the respective first and second predetermined locations.
9 more elements
Apparatus for determining the size and chemical composition of individual aerosol particles, in real time, comprising:
- means for directing a succession of individual aerosol particles along a predetermined particle path;
- means for detecting the location and size of individual aerosol particles traveling along the particle path;
- laser means for directing a beam of light at the successive aerosol particles, to desorb each particle into its component molecules and to ionize at least a portion of such molecules;
- and
- mass spectrometer means for determining the chemical composition of the ionized molecules associated with each desorbed particle;
- wherein the means for detecting includes
- first detection means for directing a first beam of light across the particle path, at a first predetermined location, and for detecting light scattered from the particle path due to impingement of the first beam of light on an aerosol particle traveling along the path,
- second detection means for directing a second beam of light across the particle path, at a second predetermined location, downstream of the first predetermined location, and for detecting light scattered from the particle path due to impingement of the second beam of light on an aerosol particle traveling along the path, and
- timing means for measuring the time delay between detection of scattered light by the first detection means and detection of scattered light by the second detection means, such time delay indicating the speed, and thus the aerodynamic size, of the associated particle;
- and wherein the first and second detection means are configured to direct the respective first and second beams of light along paths that are substantially perpendicular to each other and that are in transverse planes oriented substantially perpendicular to the particle path, such that aerosol particles are impinged on by both beams only if they travel along the particle path.
7 more elements
A method for determining the size and chemical composition of individual aerosol particles, in real time, comprising:
- using a multiple-stage vacuum system to direct a succession of individual aerosol particles along a predetermined particle path, wherein the successive stages of the vacuum system are separated from each other by skimmers aligned along the particle path;
- adjustably moving the skimmers axially relative to each other, to vary the distances therebetween, along the particle path;
- detecting the location and aerodynamic size of individual aerosol particles traveling along the particle path;
- directing a collimated beam of light at the successive aerosol particles, to desorb each particle into its component molecules and to ionize at least a portion of such molecules;
- and
- determining the chemical composition of the ionized molecules associated with each desorbed particle.
3 more elements
A method for determining the size and chemical composition of individual aerosol particles, in real time, comprising:
- directing a succession of individual aerosol particles along a predetermined particle path;
- detecting the location and aerodynamic size of individual aerosol particles traveling along the particle path, wherein detecting includes
- directing a first beam of light across the particle path, at a first predetermined location, and detecting light scattered from the particle path due to impingement of the first beam of light on an aerosol particle traveling along the path,
- directing a second beam of light across the particle path, at a second predetermined location, downstream of the first predetermined location, and detecting light scattered from the particle path due to impingement of the second beam of light on an aerosol particle traveling along the path, and
- measuring the time delay between detection of scattered light from the first beam of light and detecting scattered light from the second beam of light, such time delay indicating the speed, and thus the aerodynamic size, of the associated particle,
- wherein directing the first and second beams of light together include generating a laser beam having multiple wavelengths and separating the laser beam into the first and second beams of light, each having a wavelength different from the other;
- directing a collimated beam of light at the successive aerosol particles, to desorb each particle into its component molecules and to ionize at least a portion of such molecules;
- and
- determining the chemical composition of the ionized molecules associated with each desorbed particle.
6 more elements
Dependencies are inferred from the claim text.