Electrospray with soft X-ray neutralizer
The electrospray generator system described herein uses a soft X-ray source instead of a radioactive source to generate bipolar ions for the neutralization of the initially charged particles. In one example, the soft X-ray source is directed at an orifice from which the charged particles emanate, thereby allowing the neutralization of the particles to happen faster than in prior art configurations and, in some instances, even neutralization occurring immediately on a droplet before it passes through the electrospray orifice.
1. An apparatus for generating aerosols comprising:
an electrospray assembly, having an electrospray inlet and a discharge outlet, for receiving a liquid sample at the electrospray inlet and electrostatically generating multiple substantially uniformly sized electrically charged droplets of the liquid sample at the discharge outlet, the electrospray assembly further including an electrospray chamber with a blocking or shielding member located adjacent and not in contact with the discharge outlet;
a mechanism for supplying the liquid sample to the electrospray assembly; and
a charge neutralizing assembly disposed in a head-on or co-linear configuration with the discharge outlet for reducing the electrical charge of each droplet of the liquid sample as the droplet exits the electrospray assembly, wherein the neutralizing assembly comprises a soft X-ray source, wherein the blocking member prevents an output of the soft X-ray source from impinging directly onto the source of the electrically charged droplets.
2. The apparatus of claim 1 wherein the discharge outlet comprises a capillary tube that forms a cone jet configuration at an exit of the tube from the liquid sample, wherein the stability of the cone jet of the liquid sample is maintained by the blocking member thereby facilitating continuous formation of droplets.
3. The apparatus of claim 1 further comprising:
an evaporation chamber defining a droplet evaporation region proximate the electrospray discharge outlet and extending downstream thereof, for reducing the size of the droplets by evaporation as the droplets progress downstream through the evaporation region, to form an aerosol of the sample; and
wherein the liquid sample comprises an electrically conductive liquid and a substantially non-volatile material uniformly dispersed throughout the liquid, wherein the aerosol includes particles of a substantially non-volatile residue consisting essentially of the material.
4. The apparatus of claim 1 further including a particle counting apparatus disposed downstream of the neutralizing assembly to receive the aerosol.
5. The apparatus of claim 4 wherein the particle counting apparatus is a condensation particle counter.
6. The apparatus of claim 4 further comprising a particle separation device disposed downstream of the neutralization assembly to receive the aerosol and separate particles of the aerosol based upon the electrical mobility of the individual particles.
7. The apparatus of claim 6 wherein the particle separation device comprises an electrostatic classifier.
8. The apparatus of claim 4 further including a particle analyzing device disposed downstream of the evaporation region to receive the aerosol.
9. The apparatus of claim 8 wherein the particle analyzing device includes an electrostatic classifier receiving the aerosol and a condensation particle counter disposed downstream of the electrostatic classifier.
10. The apparatus of claim 1 wherein the blocking member includes one of a bar member having a diameter greater than 0.1 inches or a plate member having a width greater than 0.1 inches.