Process and apparatus for adjusting an aerosol charge by using a corona discharge

Abstract

A system for analyzing aerosols incorporates a corona discharge ion generator with a positively or negatively charged corona discharge needle formed of platinum or a platinum alloy. A high speed (40-210 meter per second) air flow sweeps the ions away from the corona discharge, and propels the ions into a mixing chamber in a turbulent jet that encounters an aerosol, also provided to the mixing chamber. In one version of the ion generator, the ions are carried into the mixing chamber through an orifice formed in a positively or negatively biased plate. In another alternative, the aerosol droplets are electrostatically generated, and propelled into the mixing chamber as an aerosol jet that confronts the ion jet to enhance a mixing of the charged droplets and the ions. In this version the droplets are advantageously neutralized to leave predominantly singly charged positive and negative particles, to provide a neutralized aerosol particularly well suited for analysis with a mass spectrometer.

What is claimed is: [Claims 1-17 are canceled.] 
     
         18 . A process for characterizing a non-volatile material uniformly dispersed throughout an electrically conductive liquid, including: 
 providing a liquid sample including an electrically conductive liquid and a non-volatile material substantially uniformly dispersed throughout the liquid;    electrostatically generating multiple electrically charged droplets of the liquid sample, and entraining at least a portion of the charged droplets in a first gas flow to provide an aerosol jet;    generating multiple first ions, and entraining at least a portion of the first ions in a second gas flow to provide a first ion jet; and    causing the aerosol jet and the first ion jet to merge at a merger location, to promote a mixing of the charged droplets and the first ions to alter the droplet charges toward neutralization.    
     
     
         19 . The process of  claim 18  wherein: 
 causing the aerosol jet and the ion jet to merge comprises causing the jets to move in opposite directions towards one another.  
 
     
     
         20 . The process of  claim 18  further including: 
 evaporating the charged droplets during the altering of the droplet charges.  
 
     
     
         21 . The process of  claim 20  wherein: 
 evaporating of the droplets includes substantially drying the droplets, whereby the aerosol removed from the merger location consists essentially of particles of the non-volatile material.  
 
     
     
         22 . The process of  claim 20  wherein: 
 the altering includes adjusting the charges of the droplets at a rate sufficient to prevent the droplets from disintegrating due to repulsive Coulombic forces as they evaporate.  
 
     
     
         23 . The process of  claim 18  further including: 
 after removing the aerosol, providing the aerosol to an aerosol characterizing device.  
 
     
     
         24 . The process of  claim 23  wherein: 
 providing of the aerosol to an aerosol characterizing device comprises providing the aerosol to a mass spectrometer.  
 
     
     
         25 . The process of  claim 18  wherein: 
 the aerosol jet and the first ion jet have linear velocities of at least about 40 meters per second as they approach the merger location.  
 
     
     
         26 . The process of  claim 18  further including: 
 generating multiple second ions having electrical charges opposite to the charges of the first ions, and entraining at least a portion of the second ions in a third gas flow to provide a second ion jet; and  
 causing the second ion jet to merge with the aerosol jet and the first ion jet at the merger location.  
 [Claims  27 - 44  are canceled.] 
 
     
     
         45 . A process for ionizing an aerosol, including: 
 generating an aerosol;    using a corona discharge member formed of a nobel metal to generate multiple first ions, and providing a first gas flow past the discharge member to entrain at least a portion of the first ions in the gas flow to provide a first ion carrying jet; and    causing the first ion carrying jet to merge with the aerosol at a selected location, to promote a mixing of the ions with the aerosol to alter an electrical charge distribution of the aerosol.    
     
     
         46 . The process of  claim 45  wherein: 
 using the discharge member to generate the ions comprises applying an ionizing current to the discharge member in the range including from about 10 microamperes to about 20 microamperes.  
 
     
     
         47 . The process of  claim 45  wherein: 
 generating the aerosol comprises electrostatically generating multiple electrically charged droplets of a liquid sample that includes an electrically conductive liquid and a non-volatile material dispersed substantially uniformly throughout the liquid, and entraining at least a portion of the charged droplets in a second gas flow to provide an aerosol jet; and  
 wherein causing the aerosol and the first ion carrying jet to merge comprises causing the aerosol jet and the first ion carrying jet to move in opposite directions towards one another.  
 
     
     
         48 . The process of  claim 47  further including: 
 evaporating the electrically charged droplets during the altering of the charge distribution.  
 
     
     
         49 . The process of  claim 48  wherein: 
 evaporating the droplets includes substantially drying the droplets, whereby the aerosol after said altering consists essentially of particles of the non-volatile material.  
 
     
     
         50 . The process of  claim 48  wherein: 
 said altering includes reducing respective charges of the droplets at a rate sufficient to prevent the droplets from disintegrating due to repulsive Coulombic forces.  
 
     
     
         51 . The process of  claim 45  further including: 
 after said altering the charge distribution, removing the aerosol from the selected location.  
 
     
     
         52 . The process of  claim 51  further including: 
 after removing the aerosol, providing the aerosol to an aerosol characterizing device.  
 
     
     
         53 . The process of  claim 52  wherein: 
 providing the aerosol to an aerosol characterizing device comprises providing the aerosol to a mass spectrometer.  
 
     
     
         54 . The process of  claim 45  wherein: 
 providing a first gas flow past the corona discharge member includes causing the gas to travel past the discharge member at a mean velocity at least about 40 meters per second.  
 
     
     
         55 . The process of  claim 45  further including: 
 generating multiple second ions having electrical charges opposite to the charges of the first ions, and causing at least a portion of the second ions to merge with the aerosol at the selected location.  
 
     
     
         56 . The process of  claim 55  wherein: 
 said using the corona discharge member to generate multiple first ions comprises biasing the corona discharge member to a first electrical polarity; and  
 wherein said generating multiple second ions comprises biasing a corona discharge element to a second electrical polarity opposite to the first electrical polarity, and providing a second gas flow past the discharge element to entrain at least a portion of the second ions in the second gas flow to provide a second ion carrying jet.  
 
     
     
         57 . The process of  claim 56  further including: 
 selectively varying the levels of the first and second electrical polarities to which the corona discharge member and the corona discharge element, respectively, are biased.  
 
     
     
         58 . The process of  claim 45  wherein: 
 said altering the charge distribution comprises altering the electrical charge distribution towards neutralizing the aerosol.  
 
     
     
         59 . The process of  claim 18  further including: 
 after altering the droplet charges toward neutralization, removing the aerosol from the merger location.  
 
     
     
         60 . The process of  claim 18  wherein: 
 said providing a first ion jet comprises causing the second gas flow and entrained first ions to travel at a mean velocity of at least about 40 meters per second.  
 
     
     
         61 . A device for altering an electrical charge distribution of an aerosol, including: 
 an enclosure defining a mixing chamber;    an aerosol generator having a droplet discharge region proximate the enclosure, and adapted to generate multiple droplets of a liquid sample at the droplet discharge region;    a first ion generator spaced apart from the droplet discharge region, and electrically biased to a first electrical polarity to generate multiple first ions at a first corona discharge region thereof proximate the enclosure;    a first flow guide for guiding a first gas flow past the droplet discharge region to entrain at least a portion of the droplets and form an aerosol of the sample, and to carry the entrained droplets into the mixing chamber; and    a second flow guide for guiding a second gas flow past the corona discharge region to entrain at least a portion of the first ions having the first electrical polarity and to carry the entrained ions toward a merger with the aerosol in the mixing chamber, to intermix the aerosol and the entrained first ions and thereby alter an electrical charge distribution of the aerosol.    
     
     
         62 . The device of  claim 61  wherein: 
 the enclosure further defines a first orifice for admitting the aerosol into the mixing chamber, and a second orifice for admitting the entrained first ions into the mixing chamber.  
 
     
     
         63 . The device of  claim 62  wherein: 
 the enclosure further defines an exit orifice permitting the aerosol to exit the mixing chamber after said altering of the charge distribution.  
 
     
     
         64 . The device of  claim 61  further including: 
 a second ion generator disposed proximate the enclosure and spaced apart from the first ion generator and the droplet discharge region, biased to a second electrical polarity opposite said first electrical polarity to generate multiple second ions at a second corona discharge region thereof;  
 a third flow guide for guiding a third gas flow past the second corona discharge region to entrain at least a portion of the second ions having said second electrical polarity and carry the entrained ions into the mixing chamber for a merger at least with the aerosol.  
 
     
     
         65 . The device of  claim 61  wherein: 
 said aerosol generator includes an electrostatic droplet generator, electrically biased to generate said multiple droplets electrically charged to a second electrical polarity opposite said first electrical polarity, whereby said altering of the electrical charge distribution tends to neutralize the aerosol.  
 
     
     
         66 . The device of  claim 61  further including: 
 an aerosol characterizing device disposed to receive the aerosol after the electrical charge distribution of the aerosol is so altered.  
 
     
     
         67 . The device of  claim 66  wherein: 
 the aerosol characterizing device is selected from the group of devices consisting of: a differential mobility analyzer in combination with either a condensation nucleus counter or an electrometer; and a mass spectrometer.  
 
     
     
         68 . The device of  claim 62  wherein: 
 the first gas flow is directed into the enclosure through the first orifice at a mean velocity of at least about 40 meters per second; and  
 the second gas flow is directed past the corona discharge region at a mean velocity of at least about 40 meters per second.  
 
     
     
         69 . The device of  claim 61  wherein: 
 the first gas flow includes a combination of air and an electronegative gas selected from the group consisting of: carbon dioxide and sulfur hexafluoride, wherein the electronegative gas constitutes at least three percent of the first gas flow.  
 
     
     
         70 . A device for adjusting the electrical charge distribution of an aerosol, including: 
 an enclosure defining a chamber adapted to receive an aerosol into the chamber from outside of the enclosure;    an ion generator electrically biased to generate multiple ions at a corona discharge region thereof;    a first flow guide for guiding the aerosol into the chamber; and    a second flow guide for guiding a gas flow past the corona discharge region to entrain at least a portion of the ions having a selected electrical polarity and carry the entrained ions toward a turbulent merger with the aerosol in the chamber, to rapidly mix the aerosol and the entrained ions and thereby alter an electrical charge distribution of the aerosol.    
     
     
         71 . The device of  claim 70  wherein: 
 the enclosure further defines a first orifice to accommodate entry of the aerosol into the chamber.  
 
     
     
         72 . The device of  claim 71  wherein: 
 the enclosure further defines a second orifice to accommodate entry of the entrained ions into the chamber.  
 
     
     
         73 . The device of  claim 71  wherein: 
 the aerosol flows through the first orifice into the chamber at a mean velocity of at least about 40 meters per second.  
 
     
     
         74 . The device of  claim 70  further including: 
 an aerosol characterizing device disposed to receive the aerosol after the electrical charge distribution is so altered.  
 
     
     
         75 . The device of  claim 74  wherein: 
 the aerosol characterizing device is selected from the group of devices consisting of:  
 a differential mobility analyzer in combination with either a condensation nucleus counter or an electrometer; and  
 a mass spectrometer.  
 
     
     
         76 . The device of  claim 70  wherein: 
 the aerosol includes a plurality of droplets suspended in a carrier gas, and the carrier gas includes air in combination with an electronegative gas selected from the group consisting of: carbon dioxide and sulfur hexafluoride, wherein the electronegative gas constitutes at least three percent of the carrier gas.