Apparatus and method for focusing and selecting ions and charged particles at or near atmospheric pressure

Apparatus for the focusing and selecting of an aerosol of gas-phase ions or charged particles at or near atmospheric pressure, the apparatus comprising:

• a. a source of ions or charged particles;
• b. a concentric flow of gas;
• c. a first conductive high-transmission element composed of a surface populated with a plurality of holes and an entrance lens through which gases and substantially all said ions pass unobstructed into an RF/DC quadrupole, the said surface and entrance lens being supplied with an attracting electric potential by connection to a high voltage supply, and generating an electrostatic field between the said source of ions, from atmospheric ion source, and the top side of said surface;
• d. a RF/DC quadrupole assembly for receiving and transmitting gas and focused ions along the z-axis, the said quadrupole being supplied with both RF and DC electric potentials by connection to a high voltage supply or quadrupole controller so that said quadrupole assembly may act as a mass filter for said ions and generating an electrostatic field between backside of said entrance lens and said quadrupole assembly and operating at a pressure and voltage as not to form an electrical discharge;
• e. a second conductive high-transmission element composed of a second surface populated with a plurality of holes and an exit lens so that substantially all said ions and gas exiting said quadrupole assembly pass unobstructed through said second element toward a small cross-sectional area in an aperture or capillary tube, the said second surface and exit lens being supplied with an attracting electric potential by connection to a high voltage supply, and generating an electrostatic field between the said quadrupole assembly and the top side of said second high transmission surface, while said gas exits through a gas exhaust and aperture;
• f. an aperture or capillary tube for receiving substantially all said ions, the said aperture being supplied with an attracting electrostatic potential, and generating an electrostatic field between the backside of said exit lens and said aperture whereby electric field lines are concentrated to a small cross-sectional area on said aperture;
• g. an analytical apparatus in communication with the said aperture, wherein said aperture is sandwiched between said exit lens and the analytical apparatus, said cross-sectional area of ions being directed through said aperture into said analytical apparatus, whereby to provide detection of ions separated at or near atmospheric pressure through said quadrupole mass filter.

A method of mass analysis at atmospheric pressure utilizing an ion source region, a focusing region, a RF/DC quadrupole region, and detector region, admitting a concentric flow of gas into said ion source region so that a gas-phase ion and gas may travel through said focusing region, said RF/DC quadrupole region, and into said detector region, and said method comprising:

• a. producing ions of a trace substance in said ion source region,
• b. directing said gas and ions through a first high transmission element in said focusing region into a RF/DC quadrupole in said RF/DC quadrupole region, first through said focusing region, and then through said RF/DC quadrupole region, and then detecting the ions in said detector region which have passed through said RF/DC quadrupole region, to analyze said substance,
• c. placing DC potentials on said first high transmission element so that said first high transmission element acts to guide and focus ions therethrough,
• d. placing RF and DC potentials on said RF/DC quadrupole so that said RF/DC quadrupole acts as a mass filter,
• e. gas exiting said detector region through gas exhaust,
• whereby to provide a means of determining the mass of said ions at atmospheric pressure.