CA2167099A1 - Particulate analysis of fluid samples - Google Patents
Particulate analysis of fluid samplesInfo
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- CA2167099A1 CA2167099A1 CA 2167099 CA2167099A CA2167099A1 CA 2167099 A1 CA2167099 A1 CA 2167099A1 CA 2167099 CA2167099 CA 2167099 CA 2167099 A CA2167099 A CA 2167099A CA 2167099 A1 CA2167099 A1 CA 2167099A1
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Abstract
The present invention provides apparatus and methods for analyzing the particulate content of liquid samples. In an exemplary embodiment, the invention relates to a particle-analyzing apparatus comprising a liquid removal portion and a particle analyzing portion. In the liquid removal portion, the apparatus comprises a droplet formation portion for generating a droplet-laden gas stream from a liquid sample to be analyzed. Communicating with the droplet formation portion is a liquid removal portion.
The liquid removal portion receives the droplet-laden gas stream generated by the droplet formation portion and substantially removes the liquid from the received droplet-laden gas stream to create a particle-laden gas stream. The particle-laden gas stream is transported to a particle analyzer for evaluating the particles entrained in the particle-laden gas stream. Particle evaluation can range from rudimentary particle counting to more sophisticated real-time analysis of particle quantities and compositions.
The liquid removal portion receives the droplet-laden gas stream generated by the droplet formation portion and substantially removes the liquid from the received droplet-laden gas stream to create a particle-laden gas stream. The particle-laden gas stream is transported to a particle analyzer for evaluating the particles entrained in the particle-laden gas stream. Particle evaluation can range from rudimentary particle counting to more sophisticated real-time analysis of particle quantities and compositions.
Description
PARTICUT ~TF. ANAI YSIS OF FT UID SAMPI FS
Field of the Illvention The present invention relates to particle analysis and, more particularly, to S analysis of the particulate content of liquid samples.
~ronnd of the Ir~vQntio~
Particle detection and analysis is desirable in a variety of m~nllf~cturing and environmental contexts. As used herein, the terms "particle" and "particulate" refer to a 10 minute quantity or fragment of an element, compound, composition, or mixture. When used to describe subsl~ces in liquids, the terms "particle" and "particulate" describe a small quantity of suspended or dissolved nonvolatile material. In clean rooms used for the fabrication of integrated circuits, highly accurate particle detection is required due to the small tlim~ ions of the devices under production. Significant failure rates in 15 integrated circuits are associated with the presence of particles greater than one-tenth the device line~vidth. Typically, the smaller the size of the particle, the greater the number of particles that are present. The.efo.~, as linewidths decrease ~vithin the sub-micron range, particle removal becomes increasingly difficult and costly. Consequently, control of a particle source is usually more cost-effective than removal of particles once they are 20 liberated from their source. Through real-time particle analysis, particle sources can be identified and controlled.
For particles suspended or dissolved in liquids, accurate particle detection andanalysis is difficult beca~se many particle counting and evaluation techniques require separation of the particles from their liquid carriers. Conventional particle separation 25 methods, such as filtration, do not adequately capture very fine particulates, resulting in imprecise particle ~ses~ nt Compositional analysis of the filtrate is hindered by resolution of the analytical tool; particles smaller than the resolution of the analytical tool used for evaluation are overwhelmed by the filtering medium. Further, filtration does not permit real-time analysis of particle quantities, sizes, and compositions and thus does not 30 provide definitive information concerning particle gen~.alion events.
Quantitative analysis of particles while present in a carrier liquid gives an indication of particle e~ietence, but yields no compositional information. Consequently, there is a need in the art for improved systems for separating suspended or dissolved particles from their carrier liquids to facilitate quantitative, size, and/or compositional analysis of the particulate content of liquids.
For particles that are present in gases, such as particles entrained in air, particle detection and analysis is typically performed by counting of airborne particles followed 5 by off-line analysis of deposited particles through microscopic or laser scan techniques.
The former technique provides the rapid response required for monitoring particle generation events while the latter technique provides size and elemental composition information. Particle counting is frequently perforrned using standard light-scattering particle counters. However, these devices can only detect particles on the order of 50 10 nanometers or greater and provide no compositional information. While off-line analysis provides particle composition inforrnation, it too is limited by the particle sizes it can detect and cannot be time-correlated to particle generation events.
Mass spectrometry is an analytical technique used for the accurate deterrnination of molecular weights, identification of chemical structures, determination of mixture 15 compositions, and ~ ive elemental analysis. Molecular structure is typically determined from the fragmentation pattern of the ions formed when the molecule is ionized. Elemental content of molecules is determined from mass values obtained from using mass spectrometers. However, since mass spectrometers typically operate invacuum, particulate analysis of gases or liquids usually requires that nearly all of the 20 particulate carrier be separated from the particulate material prior to ionization in the sl.ecl~ollleter. This requirement increases the complexity of particle detection for particulates present in liquids and gases.
More universal detection can be achieved through electron impact ionization of neutral species ejected by the collision of a particle beam with a heated surface.
25 However, this method creates extensive fragmentation and results in lower ionization yields than surface ionization. Sc~nning mass analyzers, such as the quadrapole or m~pnPtic sector analyærs, can also be used for particulate analysis. Due to the transient nature of the signal produced, it is difficult or impossible to obtain a complete mass spectrum. As a result, these analyzers show poor sensitivity and difficulty in performing 30 multico."~onent determin~tions.
Many of the difficulties associated with the above techniques for analyzing the particulate contents of gas strearns can be reduced or elimin~t~d through the use of a laser-assisted mass spectrometry system taught in U.S. Patent No. 5,382,794, issued ~ 3 ~ 2167099 -January 17, 1995, commonly assignèd to the instant assignee, the disclosure of which is incorporated by reference herein. In the patent, an exemplary laser-assisted mass spectrometry system is described in which particles enter an evacuable chamber through an inlet device such as a capillary. A laser, such as a pulsed laser, is positioned such that 5 the laser beam intersects the particle stream. As the particles pass through the path of the laser beam, they are fragmented and ionized. A detector, such as a time of flight mass spectrometer, detects the ionized species. Mass spectra are produced, typically recorded with an oscilloscope, and analyzed with a microprocessor. The mass spectra information permits real-time analysis of the particle size and composition.
While the laser-based system of the patent is advantageous for the real-time analysis of airborne particles, there is a need in the art for systems configured to analyze the particulate content of liquids. Such systems would be useful in analyzing chemical reactions, liquids used in semiconductor manufacturing, hazardous liquid materials, and non-volatile colllponents present in separation techniques such as liquid chromatography.
~mt~ry of the Invention The present invention provides appardlus and methods for analyzing the particulate content of liquid samples. In an exemplary embodiment, the invention relates to a particle-analyzing appa~L~Is comprising a liquid removal portion and a particle analyzing portion. In the liquid removal portion, the apparatus comprises a droplet formation portion for gene,dtiilg a droplet-laden gas strearn from a liquid sample to be analyzed. Coll~ icating with the droplet formation portion is a liquid removal portion.
The liquid removal portion receives the droplet-laden gas stream generated by the droplet formation portion and sl~bst~nti~lly removes the liquid from the received droplet-laden gas strearn to create a particle-laden gas stream. The particle-laden gas stream is tlallsl~olled to a particle analysis section for evaluating the patticles entrained in the particle-laden gas stream. Particle evaluation can range from ru~iment~y particle counting to more sophisticated real-time analysis of particle quantities, sizes, and compositions.
In one particular embodiment, the particle analysis section comprises a laser-assisted particle analyzer. The laser-assisted particle analyzer comprises an evacuable chamber having an entrance through which the particle-laden gas stream enters. A laser is positioned to produce a laser beam which intersects the particle laden gas stream, the ~ 4 ~ 2 1 67099 laser beam having a power density sufficient to fragment and ionize particles entrained in the particle-laden gas stream. A detector, such as a time-of-flight mass spectrometer, detects the ionized species. Practice of the present invention yields information about the particulate content of liquids, from simple particle quantities to real-time quantity and S compositional information, depending upon the selected analysis portion.
Brief Descr~p~on of the Dr~
FIG. 1 schematically depicts a carrier liquid removal system for analyzing the particulate content of liquids according to the present invention.
FIG. 2 schematically depicts an enlarged cross-section of a diffusion drying element of the carrier liquid removal system of FIG. 1.
FIG. 3 depicts a laser particle analyzer in partial cross-section useful in conjunction with the carrier liquid removal system of FIG. l.
FIG. 4 depicts a further laser particle analyzer in partial cross-section useful in lS conjunction with the carrier liquid removal system of FIG. 1.
Detailed Der~ lior~
Referring now to the drawings in detail in which like numerals indicate the sameor similar elements in each of the several views, FIG. 1 depicts a carrier liquid removal system l O0 according to one embodiment of the present invention. Carrier liquidremoval system 100 comprises droplet formation portion 110 coupled to drying portion 120. Droplet formation portion l l O is typically an atomizer capable of droplet formation on the order of 0.001-100 microns in diameter. Exemplary sources include generators with ultrasonic nebulizers and atomizers. The resultant droplet-laden gas stream enters drying portion 120 through drying portion conduit 122 for carrier liquid removal. Drying portion 120 includes a plurality of diffusion drying elements 130, best seen in FIG. 2, e.ap~ed with at least one heated zone 140.
As depicted in FIG. 2, each diffusion drying element 130 includes a tubular mesh132 substantially concentric with the cylindrical conduit housing portion 136. Positioned between housing portion 136 and mesh 132 is a particulate carrier liquid removalsubstance 134. In an exemplary embodiment, the carrier liquid removal substance 134 is a molecular sieve such as a zeolite. In particular, zeolites with a pore size of 4A are effective for removing carrier liquids comprising water, while zeolites with pore sizes of 1 3X are effective for removing carrier liquids comprising other solvents. However, other pore sizes can also be employed. Generally, the diffusion drying elements have a length on the order of 0.5 meter with an outer diameter on the order of 0.1 meter and an inner mesh diameter on the order of 0.013 meter. Exemplary diffilsion drying elements are 5 commercially available from TSI, Inc. As the molecular sieve material removes the carrier liquid, the particles remain, resulting in substantially pure detection of particles without interference from the carrier liquid. .
Returning to FIG. 1, at least one heated zone 140 is inte~sl~elaed between at least two diffilsion drying elements 130. Heated zone 140 further assists in the liquid removal 10 process by raising the tempeldl~lre of the droplet-laden gas stream, driving off carrier liquid. The heated zone is typically formed from a variety of heating elements including, but not limited to resistance heating elements, inductive heaters, and radiant heaters. The heating element is positioned such that it substantially circumferentially surrounds conduit 122. An additional heated zone is optionally positioned towards the end of 15 drying portion 120 to further remove liquid from the droplet-laden gas stream.
Consequently, following removal of the liquid from the droplet-laden gas stream, a particle-laden gas stream exits liquid removal system at exit 150.
In an alternative embodiment, carrier liquid removal system 100 is used in the analysis of particle-laden gas samples which cannot be directly analyzed by a particle 20 analyzer due to carrier gas toxicity, carrier gas reactivity, or other incompatibility. In this embodiment, the incompatible gas is displaced by a substantially non-reactive or inert gas. The pores of the molecular sieve material are charged with the substantially non-reactive or inert gas. Pore-charging can be accomplished by passing the non-reactive or inert gas through system 100, thus filling the pores of the molecular sieve material 25 contained within the diffusion drying elements with the non-reactive or inert gas. This non-reactive or inert gas contained within the pores displaces the incompatible gas of the particulate-laden gas stream. In this manner, reactive or corrosive gases are precluded from entering a particle analysis system.
In both the carrier liquid removal and gas displ~cenl~t uses of system 100, the 30 particle-laden gas stream is transported from exit 150 to a particle analyzer. As used herein, the e~ ession "particle analyzer" relates to any appa,al-ls which provides size, quantity and/or compositional information about the particles entrained in the gas stream exiting system 100. The particle analyzer can be either real-time, dynamically yielding 2 1 67()99 information as the particles are analyzed, or off-line, involving collection of particles for later evaluation.
In one exemplary embodiment, particle analysis is performed using a laser-assisted particle analyzer, schematically depicted in FIG. 3. The apparatus 2 includes an 5 inlet device 3 through which particles enter an evacuable chamber 6. Typically, charnber 6 is differentially pumped by diffusion pump 7 and mechanical pump 8 to m~int~in a ,oles~lre of approximately less than or equal to 10-3 torr. Inlet device 3 includes capillary 4 fabricated from materials which provide a smooth interior surface, such as fused silica.
The inner diameter of inlet device 3 is generally on the order of 0.20 to 0.53 mm with a length on the order of 10-200 cm for particle analysis in the range of 0.001 to 10 microns.
Optionally, one or more purnped skimmers 24 are positioned adjacent the capillary outlet to assist in focusing the particle-laden gas stream through the chamber entrance. FIG. 4 depicts an alternate inlet device embodiment. In this embodiment, the inlet device comprises a pumpedjet separator capillary 5. Optionally, mechanical pumps 28 m~int~in a pressure of approximately 0.01-1.0 torr inside skimmers 22 and jet separator capillary 5 in the respective embot~iments of FIGS. I and 2.
To ionize the particles injected through the inlet device, a pulsed laser 10 is focused through an opening in chamber 6. The opening in chamber 6 is positioned such that the focused laser beam i~ e-;~ the path traveled by the particles. A time-of-flight mass spectrometer (TOF/MS) 12 obtains mass spectra created by particles ionized by laser 10. U~ile time-of-flight mass slJectro~cters are depicted in the FIGS., it is understood that these ~pe.,llv~eters are illustrative. A variety of mass spectrometers can be employed in the particle analyzers of the present invention including, but not limited to, quadrapole, m~netic sector, and quadrapole ion trap spectrometers, and Penning ion trap spectrometers such as FTICR sl,e~ L~o~eters. A transient recorder 16, such as a digital oscilloscope, records the mass spectra while computer 22 analyzes and displays the information received from oscilloscope 16.
Laser 10 is selected from pulsed lasers having a short pulse width, a high peak power, a moderate spot size, and a high repetition rate. For the embodiments shown in FIGS. 3 and 4, laser 10 has a pulse frequency in the range of 10 Hz to 10 kHz with a frequency of from 1 to 10 kHz being preferred. The laser power is approximately S mJ or greater with a power density on the order of at least 1.5 x 1 o8 W/cm2. Laser spot sizes are determine~ by the selected laser power and power density and are generally between 0.001 to 2 mm2, although other spot sizes are acceptable. Commercially-available lasers for use in the particle analyzer of FIGS. 3 and 4 include a Lambda Physik excimer laser, model EMG 202, and a Spectra Physics DCR Il Neodymium YAG laser.
Time-of-flight mass spectrometer 12, as depicted in FIGS. 3 and 4, is a dual 5 positive and negative time-of-flight mass spectrometer. The spectrometer counts each fragmentation incident and measures the masses and yields of both positive and negative ions produced when the particle beam contacts the laser beam. While a dual positive and negative time-of-flight mass spectrometer is shown as illustrative, it is understood that a single time-of-flight spectrometer can be employed. For example, a positive time-of-10 flight mass spectrometer can be employed when laser power densities are sufficientlyhigh to yield primarily positive ions. The mass of the ions correlates to the required travel time for the particle fragment to contact the detector. A Jordan Associates dual time-of-flight mass spectrometer can be employed as mass spectrometer 12. Further details concerning the appa~ s of FIGS. 3 and 4 and their operation are found in the aforementionéd U.S. Patent No. 5,382,794, discussed above.
It is emphasized that the particle analyzers of FIGS. 3 and 4 are merely exemplary and that any particle analyzer can be used in conjunction with the carrier liquid removal system of the present invention. Other particle analyzers useful in conjunction with system 100 include, but are not limited to, particle counters such as light-scattering particle counters and differential mobility particle analyzers, and compositional analyzers such as Auger spectroscopy, and x-ray analyzers (particularly when coupled with sc~nnin~ electron microscopy (SEM)). Additionally, liquid removal systems other than that depicted in FIG. 1 can be used for carrier liquid removal of particulate-cont~inin~
fluid samples. Any system which removes liquid from a particle-laden liquid sarnple to create a particle-laden gæ stream can be employed in the particulate analysis of liquid samples according to the present invention. A liquid removal system suitable for use in the present invention is described in published PCT Application No. WO 93/05379, the disclosure of which is incorporated herein by reference. Other laser-assisted particle analyzers employable in the present invention are disclosed in copending U.S. Patent Application Serial No. 08/_, , filed January 17, 1995, (Attomey Docket No. Reents 4) assigned to the assignee of the instant application, the disclosure of which is incorporated by reference herein.
The present invention can be used to monitor the particulate content of numerousliquids employed in industrial processes or discharged as effluents from industrial processes. In one exemplary embodiment, system 100 is employed in chromatographyapplications as an interface with a liquid chromatograph. The present invention applies to 5 the monitoring of hazardous materials, e.g., chlorinated organics in water systems, radioactive cont~min~ntc in liquids (e.g., groundwater) near radioactive waste storage sites as well as to the monitoring of heavy metal cont~min~nt~ and chlorine and fluorine additives in municipal water supplies. Through real-time analysis, cont~min~tion can be immediately discovered, rather than the lengthy time currently required to receive off-line 10 analysis.
While the invention has been described in terms of the foregoing exemplary embodiments, it will be readily apparent that numerous changes and modifications can be made. Accordingly, modifications such as those suggested above, but not limited thereto, are considered to be within the scope of the claimed invention.
Field of the Illvention The present invention relates to particle analysis and, more particularly, to S analysis of the particulate content of liquid samples.
~ronnd of the Ir~vQntio~
Particle detection and analysis is desirable in a variety of m~nllf~cturing and environmental contexts. As used herein, the terms "particle" and "particulate" refer to a 10 minute quantity or fragment of an element, compound, composition, or mixture. When used to describe subsl~ces in liquids, the terms "particle" and "particulate" describe a small quantity of suspended or dissolved nonvolatile material. In clean rooms used for the fabrication of integrated circuits, highly accurate particle detection is required due to the small tlim~ ions of the devices under production. Significant failure rates in 15 integrated circuits are associated with the presence of particles greater than one-tenth the device line~vidth. Typically, the smaller the size of the particle, the greater the number of particles that are present. The.efo.~, as linewidths decrease ~vithin the sub-micron range, particle removal becomes increasingly difficult and costly. Consequently, control of a particle source is usually more cost-effective than removal of particles once they are 20 liberated from their source. Through real-time particle analysis, particle sources can be identified and controlled.
For particles suspended or dissolved in liquids, accurate particle detection andanalysis is difficult beca~se many particle counting and evaluation techniques require separation of the particles from their liquid carriers. Conventional particle separation 25 methods, such as filtration, do not adequately capture very fine particulates, resulting in imprecise particle ~ses~ nt Compositional analysis of the filtrate is hindered by resolution of the analytical tool; particles smaller than the resolution of the analytical tool used for evaluation are overwhelmed by the filtering medium. Further, filtration does not permit real-time analysis of particle quantities, sizes, and compositions and thus does not 30 provide definitive information concerning particle gen~.alion events.
Quantitative analysis of particles while present in a carrier liquid gives an indication of particle e~ietence, but yields no compositional information. Consequently, there is a need in the art for improved systems for separating suspended or dissolved particles from their carrier liquids to facilitate quantitative, size, and/or compositional analysis of the particulate content of liquids.
For particles that are present in gases, such as particles entrained in air, particle detection and analysis is typically performed by counting of airborne particles followed 5 by off-line analysis of deposited particles through microscopic or laser scan techniques.
The former technique provides the rapid response required for monitoring particle generation events while the latter technique provides size and elemental composition information. Particle counting is frequently perforrned using standard light-scattering particle counters. However, these devices can only detect particles on the order of 50 10 nanometers or greater and provide no compositional information. While off-line analysis provides particle composition inforrnation, it too is limited by the particle sizes it can detect and cannot be time-correlated to particle generation events.
Mass spectrometry is an analytical technique used for the accurate deterrnination of molecular weights, identification of chemical structures, determination of mixture 15 compositions, and ~ ive elemental analysis. Molecular structure is typically determined from the fragmentation pattern of the ions formed when the molecule is ionized. Elemental content of molecules is determined from mass values obtained from using mass spectrometers. However, since mass spectrometers typically operate invacuum, particulate analysis of gases or liquids usually requires that nearly all of the 20 particulate carrier be separated from the particulate material prior to ionization in the sl.ecl~ollleter. This requirement increases the complexity of particle detection for particulates present in liquids and gases.
More universal detection can be achieved through electron impact ionization of neutral species ejected by the collision of a particle beam with a heated surface.
25 However, this method creates extensive fragmentation and results in lower ionization yields than surface ionization. Sc~nning mass analyzers, such as the quadrapole or m~pnPtic sector analyærs, can also be used for particulate analysis. Due to the transient nature of the signal produced, it is difficult or impossible to obtain a complete mass spectrum. As a result, these analyzers show poor sensitivity and difficulty in performing 30 multico."~onent determin~tions.
Many of the difficulties associated with the above techniques for analyzing the particulate contents of gas strearns can be reduced or elimin~t~d through the use of a laser-assisted mass spectrometry system taught in U.S. Patent No. 5,382,794, issued ~ 3 ~ 2167099 -January 17, 1995, commonly assignèd to the instant assignee, the disclosure of which is incorporated by reference herein. In the patent, an exemplary laser-assisted mass spectrometry system is described in which particles enter an evacuable chamber through an inlet device such as a capillary. A laser, such as a pulsed laser, is positioned such that 5 the laser beam intersects the particle stream. As the particles pass through the path of the laser beam, they are fragmented and ionized. A detector, such as a time of flight mass spectrometer, detects the ionized species. Mass spectra are produced, typically recorded with an oscilloscope, and analyzed with a microprocessor. The mass spectra information permits real-time analysis of the particle size and composition.
While the laser-based system of the patent is advantageous for the real-time analysis of airborne particles, there is a need in the art for systems configured to analyze the particulate content of liquids. Such systems would be useful in analyzing chemical reactions, liquids used in semiconductor manufacturing, hazardous liquid materials, and non-volatile colllponents present in separation techniques such as liquid chromatography.
~mt~ry of the Invention The present invention provides appardlus and methods for analyzing the particulate content of liquid samples. In an exemplary embodiment, the invention relates to a particle-analyzing appa~L~Is comprising a liquid removal portion and a particle analyzing portion. In the liquid removal portion, the apparatus comprises a droplet formation portion for gene,dtiilg a droplet-laden gas strearn from a liquid sample to be analyzed. Coll~ icating with the droplet formation portion is a liquid removal portion.
The liquid removal portion receives the droplet-laden gas stream generated by the droplet formation portion and sl~bst~nti~lly removes the liquid from the received droplet-laden gas strearn to create a particle-laden gas stream. The particle-laden gas stream is tlallsl~olled to a particle analysis section for evaluating the patticles entrained in the particle-laden gas stream. Particle evaluation can range from ru~iment~y particle counting to more sophisticated real-time analysis of particle quantities, sizes, and compositions.
In one particular embodiment, the particle analysis section comprises a laser-assisted particle analyzer. The laser-assisted particle analyzer comprises an evacuable chamber having an entrance through which the particle-laden gas stream enters. A laser is positioned to produce a laser beam which intersects the particle laden gas stream, the ~ 4 ~ 2 1 67099 laser beam having a power density sufficient to fragment and ionize particles entrained in the particle-laden gas stream. A detector, such as a time-of-flight mass spectrometer, detects the ionized species. Practice of the present invention yields information about the particulate content of liquids, from simple particle quantities to real-time quantity and S compositional information, depending upon the selected analysis portion.
Brief Descr~p~on of the Dr~
FIG. 1 schematically depicts a carrier liquid removal system for analyzing the particulate content of liquids according to the present invention.
FIG. 2 schematically depicts an enlarged cross-section of a diffusion drying element of the carrier liquid removal system of FIG. 1.
FIG. 3 depicts a laser particle analyzer in partial cross-section useful in conjunction with the carrier liquid removal system of FIG. l.
FIG. 4 depicts a further laser particle analyzer in partial cross-section useful in lS conjunction with the carrier liquid removal system of FIG. 1.
Detailed Der~ lior~
Referring now to the drawings in detail in which like numerals indicate the sameor similar elements in each of the several views, FIG. 1 depicts a carrier liquid removal system l O0 according to one embodiment of the present invention. Carrier liquidremoval system 100 comprises droplet formation portion 110 coupled to drying portion 120. Droplet formation portion l l O is typically an atomizer capable of droplet formation on the order of 0.001-100 microns in diameter. Exemplary sources include generators with ultrasonic nebulizers and atomizers. The resultant droplet-laden gas stream enters drying portion 120 through drying portion conduit 122 for carrier liquid removal. Drying portion 120 includes a plurality of diffusion drying elements 130, best seen in FIG. 2, e.ap~ed with at least one heated zone 140.
As depicted in FIG. 2, each diffusion drying element 130 includes a tubular mesh132 substantially concentric with the cylindrical conduit housing portion 136. Positioned between housing portion 136 and mesh 132 is a particulate carrier liquid removalsubstance 134. In an exemplary embodiment, the carrier liquid removal substance 134 is a molecular sieve such as a zeolite. In particular, zeolites with a pore size of 4A are effective for removing carrier liquids comprising water, while zeolites with pore sizes of 1 3X are effective for removing carrier liquids comprising other solvents. However, other pore sizes can also be employed. Generally, the diffusion drying elements have a length on the order of 0.5 meter with an outer diameter on the order of 0.1 meter and an inner mesh diameter on the order of 0.013 meter. Exemplary diffilsion drying elements are 5 commercially available from TSI, Inc. As the molecular sieve material removes the carrier liquid, the particles remain, resulting in substantially pure detection of particles without interference from the carrier liquid. .
Returning to FIG. 1, at least one heated zone 140 is inte~sl~elaed between at least two diffilsion drying elements 130. Heated zone 140 further assists in the liquid removal 10 process by raising the tempeldl~lre of the droplet-laden gas stream, driving off carrier liquid. The heated zone is typically formed from a variety of heating elements including, but not limited to resistance heating elements, inductive heaters, and radiant heaters. The heating element is positioned such that it substantially circumferentially surrounds conduit 122. An additional heated zone is optionally positioned towards the end of 15 drying portion 120 to further remove liquid from the droplet-laden gas stream.
Consequently, following removal of the liquid from the droplet-laden gas stream, a particle-laden gas stream exits liquid removal system at exit 150.
In an alternative embodiment, carrier liquid removal system 100 is used in the analysis of particle-laden gas samples which cannot be directly analyzed by a particle 20 analyzer due to carrier gas toxicity, carrier gas reactivity, or other incompatibility. In this embodiment, the incompatible gas is displaced by a substantially non-reactive or inert gas. The pores of the molecular sieve material are charged with the substantially non-reactive or inert gas. Pore-charging can be accomplished by passing the non-reactive or inert gas through system 100, thus filling the pores of the molecular sieve material 25 contained within the diffusion drying elements with the non-reactive or inert gas. This non-reactive or inert gas contained within the pores displaces the incompatible gas of the particulate-laden gas stream. In this manner, reactive or corrosive gases are precluded from entering a particle analysis system.
In both the carrier liquid removal and gas displ~cenl~t uses of system 100, the 30 particle-laden gas stream is transported from exit 150 to a particle analyzer. As used herein, the e~ ession "particle analyzer" relates to any appa,al-ls which provides size, quantity and/or compositional information about the particles entrained in the gas stream exiting system 100. The particle analyzer can be either real-time, dynamically yielding 2 1 67()99 information as the particles are analyzed, or off-line, involving collection of particles for later evaluation.
In one exemplary embodiment, particle analysis is performed using a laser-assisted particle analyzer, schematically depicted in FIG. 3. The apparatus 2 includes an 5 inlet device 3 through which particles enter an evacuable chamber 6. Typically, charnber 6 is differentially pumped by diffusion pump 7 and mechanical pump 8 to m~int~in a ,oles~lre of approximately less than or equal to 10-3 torr. Inlet device 3 includes capillary 4 fabricated from materials which provide a smooth interior surface, such as fused silica.
The inner diameter of inlet device 3 is generally on the order of 0.20 to 0.53 mm with a length on the order of 10-200 cm for particle analysis in the range of 0.001 to 10 microns.
Optionally, one or more purnped skimmers 24 are positioned adjacent the capillary outlet to assist in focusing the particle-laden gas stream through the chamber entrance. FIG. 4 depicts an alternate inlet device embodiment. In this embodiment, the inlet device comprises a pumpedjet separator capillary 5. Optionally, mechanical pumps 28 m~int~in a pressure of approximately 0.01-1.0 torr inside skimmers 22 and jet separator capillary 5 in the respective embot~iments of FIGS. I and 2.
To ionize the particles injected through the inlet device, a pulsed laser 10 is focused through an opening in chamber 6. The opening in chamber 6 is positioned such that the focused laser beam i~ e-;~ the path traveled by the particles. A time-of-flight mass spectrometer (TOF/MS) 12 obtains mass spectra created by particles ionized by laser 10. U~ile time-of-flight mass slJectro~cters are depicted in the FIGS., it is understood that these ~pe.,llv~eters are illustrative. A variety of mass spectrometers can be employed in the particle analyzers of the present invention including, but not limited to, quadrapole, m~netic sector, and quadrapole ion trap spectrometers, and Penning ion trap spectrometers such as FTICR sl,e~ L~o~eters. A transient recorder 16, such as a digital oscilloscope, records the mass spectra while computer 22 analyzes and displays the information received from oscilloscope 16.
Laser 10 is selected from pulsed lasers having a short pulse width, a high peak power, a moderate spot size, and a high repetition rate. For the embodiments shown in FIGS. 3 and 4, laser 10 has a pulse frequency in the range of 10 Hz to 10 kHz with a frequency of from 1 to 10 kHz being preferred. The laser power is approximately S mJ or greater with a power density on the order of at least 1.5 x 1 o8 W/cm2. Laser spot sizes are determine~ by the selected laser power and power density and are generally between 0.001 to 2 mm2, although other spot sizes are acceptable. Commercially-available lasers for use in the particle analyzer of FIGS. 3 and 4 include a Lambda Physik excimer laser, model EMG 202, and a Spectra Physics DCR Il Neodymium YAG laser.
Time-of-flight mass spectrometer 12, as depicted in FIGS. 3 and 4, is a dual 5 positive and negative time-of-flight mass spectrometer. The spectrometer counts each fragmentation incident and measures the masses and yields of both positive and negative ions produced when the particle beam contacts the laser beam. While a dual positive and negative time-of-flight mass spectrometer is shown as illustrative, it is understood that a single time-of-flight spectrometer can be employed. For example, a positive time-of-10 flight mass spectrometer can be employed when laser power densities are sufficientlyhigh to yield primarily positive ions. The mass of the ions correlates to the required travel time for the particle fragment to contact the detector. A Jordan Associates dual time-of-flight mass spectrometer can be employed as mass spectrometer 12. Further details concerning the appa~ s of FIGS. 3 and 4 and their operation are found in the aforementionéd U.S. Patent No. 5,382,794, discussed above.
It is emphasized that the particle analyzers of FIGS. 3 and 4 are merely exemplary and that any particle analyzer can be used in conjunction with the carrier liquid removal system of the present invention. Other particle analyzers useful in conjunction with system 100 include, but are not limited to, particle counters such as light-scattering particle counters and differential mobility particle analyzers, and compositional analyzers such as Auger spectroscopy, and x-ray analyzers (particularly when coupled with sc~nnin~ electron microscopy (SEM)). Additionally, liquid removal systems other than that depicted in FIG. 1 can be used for carrier liquid removal of particulate-cont~inin~
fluid samples. Any system which removes liquid from a particle-laden liquid sarnple to create a particle-laden gæ stream can be employed in the particulate analysis of liquid samples according to the present invention. A liquid removal system suitable for use in the present invention is described in published PCT Application No. WO 93/05379, the disclosure of which is incorporated herein by reference. Other laser-assisted particle analyzers employable in the present invention are disclosed in copending U.S. Patent Application Serial No. 08/_, , filed January 17, 1995, (Attomey Docket No. Reents 4) assigned to the assignee of the instant application, the disclosure of which is incorporated by reference herein.
The present invention can be used to monitor the particulate content of numerousliquids employed in industrial processes or discharged as effluents from industrial processes. In one exemplary embodiment, system 100 is employed in chromatographyapplications as an interface with a liquid chromatograph. The present invention applies to 5 the monitoring of hazardous materials, e.g., chlorinated organics in water systems, radioactive cont~min~ntc in liquids (e.g., groundwater) near radioactive waste storage sites as well as to the monitoring of heavy metal cont~min~nt~ and chlorine and fluorine additives in municipal water supplies. Through real-time analysis, cont~min~tion can be immediately discovered, rather than the lengthy time currently required to receive off-line 10 analysis.
While the invention has been described in terms of the foregoing exemplary embodiments, it will be readily apparent that numerous changes and modifications can be made. Accordingly, modifications such as those suggested above, but not limited thereto, are considered to be within the scope of the claimed invention.
Claims (7)
1. Apparatus for analyzing the particulate content of liquid samples comprising:a droplet formation portion for generating a droplet-laden gas stream from a liquid sample to be analyzed;
a liquid removal portion for receiving the droplet-laden gas stream generated by the droplet formation portion, the liquid removal portion comprising a conduit for transporting the droplet-laden gas steam, the conduit having at least one diffusion drying element positioned in the path of the droplet-laden gas stream and at least one heated zone for heating the droplet-laden gas stream, the liquid removal portion substantially removing the liquid from the received droplet-laden gas stream to create a particle-laden gas stream; and means for receiving the particle-laden gas stream and analyzing the particles entrained in the particle-laden gas stream.
a liquid removal portion for receiving the droplet-laden gas stream generated by the droplet formation portion, the liquid removal portion comprising a conduit for transporting the droplet-laden gas steam, the conduit having at least one diffusion drying element positioned in the path of the droplet-laden gas stream and at least one heated zone for heating the droplet-laden gas stream, the liquid removal portion substantially removing the liquid from the received droplet-laden gas stream to create a particle-laden gas stream; and means for receiving the particle-laden gas stream and analyzing the particles entrained in the particle-laden gas stream.
2. Apparatus for analyzing the particulate content of liquid samples according to claim 1 wherein the diffusion drying element includes a molecular sieve.
3. Apparatus for analyzing the particulate content of liquid samples according to claim 2 wherein the molecular sieve is a zeolite.
4. Apparatus for analyzing the particulate content of liquid samples according to claim 1 wherein the means for receiving the particle-laden gas stream and analyzing the particles entrained in the particle-laden gas stream comprises a laser-assisted particle analyzer.
5. Apparatus for analyzing the particulate content of liquid samples comprising:a droplet formation portion for generating a droplet-laden gas stream from a liquid sample to be analyzed;
a liquid removal portion for receiving the droplet-laden gas stream generated by the droplet formation portion, the liquid removal portion substantially removing the liquid from the received droplet-laden gas stream to create a particle-laden gas stream;
a particle-analyzing portion comprising an evacuable chamber including a chamber entrance through which a particle-laden gas stream enters, a laser positioned to produce a laser beam which intersects the particle-laden gas stream, the laser beam having a power density sufficient to fragment and ionize particles entrained in the particle-laden gas stream, and a detector for detecting ionized species; and an inlet device for receiving the particle-laden gas stream from the liquid removal portion; the inlet device communicating with the evacuable chamber entrance for having the particle-laden gas stream to the evacuable chamber for particle analysis.
a liquid removal portion for receiving the droplet-laden gas stream generated by the droplet formation portion, the liquid removal portion substantially removing the liquid from the received droplet-laden gas stream to create a particle-laden gas stream;
a particle-analyzing portion comprising an evacuable chamber including a chamber entrance through which a particle-laden gas stream enters, a laser positioned to produce a laser beam which intersects the particle-laden gas stream, the laser beam having a power density sufficient to fragment and ionize particles entrained in the particle-laden gas stream, and a detector for detecting ionized species; and an inlet device for receiving the particle-laden gas stream from the liquid removal portion; the inlet device communicating with the evacuable chamber entrance for having the particle-laden gas stream to the evacuable chamber for particle analysis.
6. Apparatus for analyzing the particulate content of liquid samples according to claim 5 wherein the liquid removal portion comprises at least one diffusion drying element and at least one heated zone.
7. Apparatus for analyzing the particulate content of liquid samples according to claim 6, wherein the diffusion drying element includes molecular sieve material.8. Apparatus for analyzing the particulate content of liquid samples according to claim 7 wherein the molecular sieve material is a zeolite.
9. Apparatus for analyzing the particulate content of liquid samples according to claim 5 wherein the laser has a power density of at least 1.5 x 108 W/cm2.
10. Apparatus for analyzing the particulate content of a gas stream which includes corrosive, toxic, or reactive gases, the apparatus comprising:
a fluid removal portion for receiving a particulate-laden gas stream, the particulate-laden gas stream including a corrosive, toxic, or reactive gas, the fluid removal portion comprising a conduit for transporting the particulate-laden gas stream, the conduit having at least one diffusion element positioned in the path of the paticulate-laden gas stream, and means for charging the diffusion element with a substantially non-reactive or inert gas, the fluid removal portion substantially removing corrosive, toxic, and-reactive gas from the received particle-laden gas stream, and replacing the corrosive, toxic, or reactive gas of the particle-laden gas stream with a substantially non-reactive or inert gas; and means for receiving the particle-laden gas stream from the fluid removal system and analyzing the particles entrained in the particle-laden gas stream.
11. Apparatus for analyzing the particulate content of a gas stream which includes corrosive, toxic, or reactive gases according to claim 10 wherein the diffusion element comprises a molecular sieve.
12. Apparatus for analyzing the particulate content of a gas stream which includes corrosive, toxic, or reactive gases according to claim 11 wherein the molecular sieve comprises a zeolite.
13. A method for analyzing the particulate content of liquid samples comprising:providing a particulate-laden liquid sample to be analyzed to a droplet formation system;
generating a droplet-laden gas stream from the liquid sample to be analyzed;
substantially removing the liquid from the droplet-laden gas stream by passing the droplet-laden gas stream through a liquid removal system comprising a conduit for transporting the droplet-laden gas stream, the conduit having at least one diffusion drying element positioned in the path of the droplet-laden gas stream and at least one heated zone for heating the droplet-laden gas stream, the liquid removal portion substantially removing the liquid from the received droplet-laden gas stream to create a particle laden gas stream; and transporting the particle-laden gas stream to a particle analyzer and analyzing the particles entrained in the particle-laden gas stream.
14. A method for analyzing the particulate content of liquid samples according to claim 13 wherein the diffusion drying element includes a molecular sieve.
15. A method for analyzing the particulate content of liquid samples according to claim 14 wherein the molecular sieve is a zeolite.
16. A method for analyzing the particulate content of liquid samples according to claim 13 wherein particle analyzing technique comprises a laser-assisted particle analyzing technique.
17. A method for analyzing the particulate content of a gas stream which includes corrosive, toxic, or reactive gases, the method comprising:
transporting a particulate-laden gas stream comprising corrosive, toxic, or reactive gases to a fluid removal system which includes at least one diffusion element;
charging the diffusion element with a substantially non-reactive or inert gas;
replacing the corrosive, toxic, or reactive gas of the particle-laden gas stream with the substantially non-reactive or inert gas in the charged diffusion element;
and analyzing the particles entrained in the particle-laden gas stream.
9. Apparatus for analyzing the particulate content of liquid samples according to claim 5 wherein the laser has a power density of at least 1.5 x 108 W/cm2.
10. Apparatus for analyzing the particulate content of a gas stream which includes corrosive, toxic, or reactive gases, the apparatus comprising:
a fluid removal portion for receiving a particulate-laden gas stream, the particulate-laden gas stream including a corrosive, toxic, or reactive gas, the fluid removal portion comprising a conduit for transporting the particulate-laden gas stream, the conduit having at least one diffusion element positioned in the path of the paticulate-laden gas stream, and means for charging the diffusion element with a substantially non-reactive or inert gas, the fluid removal portion substantially removing corrosive, toxic, and-reactive gas from the received particle-laden gas stream, and replacing the corrosive, toxic, or reactive gas of the particle-laden gas stream with a substantially non-reactive or inert gas; and means for receiving the particle-laden gas stream from the fluid removal system and analyzing the particles entrained in the particle-laden gas stream.
11. Apparatus for analyzing the particulate content of a gas stream which includes corrosive, toxic, or reactive gases according to claim 10 wherein the diffusion element comprises a molecular sieve.
12. Apparatus for analyzing the particulate content of a gas stream which includes corrosive, toxic, or reactive gases according to claim 11 wherein the molecular sieve comprises a zeolite.
13. A method for analyzing the particulate content of liquid samples comprising:providing a particulate-laden liquid sample to be analyzed to a droplet formation system;
generating a droplet-laden gas stream from the liquid sample to be analyzed;
substantially removing the liquid from the droplet-laden gas stream by passing the droplet-laden gas stream through a liquid removal system comprising a conduit for transporting the droplet-laden gas stream, the conduit having at least one diffusion drying element positioned in the path of the droplet-laden gas stream and at least one heated zone for heating the droplet-laden gas stream, the liquid removal portion substantially removing the liquid from the received droplet-laden gas stream to create a particle laden gas stream; and transporting the particle-laden gas stream to a particle analyzer and analyzing the particles entrained in the particle-laden gas stream.
14. A method for analyzing the particulate content of liquid samples according to claim 13 wherein the diffusion drying element includes a molecular sieve.
15. A method for analyzing the particulate content of liquid samples according to claim 14 wherein the molecular sieve is a zeolite.
16. A method for analyzing the particulate content of liquid samples according to claim 13 wherein particle analyzing technique comprises a laser-assisted particle analyzing technique.
17. A method for analyzing the particulate content of a gas stream which includes corrosive, toxic, or reactive gases, the method comprising:
transporting a particulate-laden gas stream comprising corrosive, toxic, or reactive gases to a fluid removal system which includes at least one diffusion element;
charging the diffusion element with a substantially non-reactive or inert gas;
replacing the corrosive, toxic, or reactive gas of the particle-laden gas stream with the substantially non-reactive or inert gas in the charged diffusion element;
and analyzing the particles entrained in the particle-laden gas stream.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US37373195A | 1995-01-17 | 1995-01-17 | |
| US373,731 | 1995-01-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2167099A1 true CA2167099A1 (en) | 1996-07-18 |
Family
ID=23473640
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2167099 Abandoned CA2167099A1 (en) | 1995-01-17 | 1996-01-12 | Particulate analysis of fluid samples |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH08240515A (en) |
| CA (1) | CA2167099A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112964625A (en) * | 2015-03-06 | 2021-06-15 | 英国质谱公司 | Cell population analysis |
-
1996
- 1996-01-12 CA CA 2167099 patent/CA2167099A1/en not_active Abandoned
- 1996-01-17 JP JP568996A patent/JPH08240515A/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112964625A (en) * | 2015-03-06 | 2021-06-15 | 英国质谱公司 | Cell population analysis |
| CN112964625B (en) * | 2015-03-06 | 2024-06-07 | 英国质谱公司 | Cell population analysis |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH08240515A (en) | 1996-09-17 |
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