# US 2015/0144779 A1 · Electron Impact Ion Source With Fast Response > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2015/0144779 A1 - Document ID: US20150144779A1 - Status: Published application - Kind: A1 - Application number: 14/397,274 - Filed: 2013-04-26 - Published: 2015-05-28 - Earliest claimed: 2012-04-26 - Assignees: Leco Corporation - Applicants: LECO Corporation - Inventors: Anatoly N. Verenchikov - Web page: https://patentgrep.com/patent/US20150144779A1 ## CPC - H01J 49/147: {with electrons, e.g. electron impact ionisation, electron attachment (H01J49/145 takes precedence)} - G01N 30/7206: {interfaced to gas chromatograph (interfaces in general for introducing or extracting samples to be analysed with specially adapted mass spectrometer, see H01J49/04)} - H01J 49/0468: {with means for heating or cooling the sample} - H01J 49/40: Time-of-flight spectrometers (H01J49/36 takes precedence) - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract A closed electron impact ion source with overall opening area of less than 30 mm2 is employed for direct and pulsed extraction into a time-flight mass spectrometer in order to enhance sensitivity and immunity to chemical noise of oil and fumes of the vacuum system. For compatibility with dual stage GC×GC separation, the source may contain an inert liner surrounded by an isothermal cage of thermally conductive material. The source inner surface may be reduced to under 100 mm2. A portion of carrier gas may be pumped down before admitting the sample and carrier gas into the source. A cooled surface may be used to condense fumes at the analysis time. ## Claims ### Claim 1 A method of mass spectrometric analysis comprising: separating an analyte mixture using two-dimensional gas chromatography to yield narrow (in-time) GC peaks; introducing an analyte flow and a carrier gas flow into a closed electron impact ion source to form analyte ions, wherein the impact ion source includes an exit aperture; sustaining enriched concentration of analyte molecules within said closed source by limiting an area of the exit aperture to between 0.1 and 1 cm2; accumulating said analyte ions within an electron beam of said closed electron impact ion source; and pulse extracting ion packets from said closed source directly into a time-of-flight mass spectrometer. ### Claim 2 (depends on 1) A method as set forth in claim 1, wherein the source includes an inner liner having an isothermal cage disposed proximate thereto, the method further comprising: maintaining the temperature of said source substantially uniform (within 10° C.). ### Claim 3 (depends on 1) A method as set forth in claim 1, wherein the closed source further comprises an inner surface having an area, and wherein a ratio of the area of the inner surface and the area of the exit aperture is between 10 and 100. ### Claim 4 (depends on 1) A method as set forth in claim 1, wherein the source includes a source vacuum chamber having a Peltier device disposed therein, the method comprising: condensing vapors and fumes within the source vacuum chamber using a surface cooled by the Peltier device. ### Claim 5 (depends on 1) A method as set forth in claim 1, further comprising: pumping down of a portion of carrier gas (inevitably causing some losses in the introduced sample amount) in front of said “closed” electron impact source. ### Claim 6 (depends on 1) A method as set forth in claim 1, wherein the closed source further comprising: electrostatically repulsing analyte ions from sides of the source and along the direction of the electron beam. ### Claim 7 (depends on 1) A method as set forth in claim 1, wherein pulse extracting ion packets comprises: operating at a high extraction frequency. ### Claim 8 (depends on 6) A method as set forth in claim 6, wherein time-of-flight mass spectrometer defines an ion time-of-flight, and wherein the pulse extraction defines a pulse period and further wherein the pulse period is shorter than the ion time-of flight. ### Claim 9 (depends on 8) A method as set forth in claim 8, wherein the mass spectrometer includes pulsed deflectors, the method comprising: selecting a narrow mass range via the pulsed deflectors. ### Claim 10 A chromato-mass spectrometer comprising: a reflecting time-of-flight analyzer having an ion mirror, a free-flight region, and a detector; a closed electron impact ion source defining one or more openings into an ionization chamber, wherein a cumulative area of the one or more openings into the ionization chamber is between 0.1 cm2 and 1 cm2, wherein the closed impact ion source includes a continuous electron beam, a repeller connected to a pulsed voltage supply and an extractor connected to the pulsed voltage supply, and wherein said ion mirror is aligned parallel with said detector and said closed ion source is tilted at small angle; and a deflector for steering ion packets at an angle that is about equal to the source tilt angle. ### Claim 11 (depends on 10) An apparatus as set forth in claim 10, wherein the cumulative area of the one or more openings is selected from the group consisting of: (i) less than 100 mm2, (ii) less than 50 mm2, (iii) less than 20 mm2; (iv) less than 10 mm2; (v) less than 5 mm2; (vi) less than 3 mm2; and (vii) less than 1 mm2; ### Claim 12 (depends on 10) An apparatus as set forth claim 10, wherein said closed electron impact ion source further comprises: an inner chemically inert liner and an isothermal cage of heat conductive material. ### Claim 13 (depends on 10) An apparatus as set forth in claim 10, wherein said closed electron impact ion source has an inner surface defining an area, and wherein a ratio of the area of the inner surface and the area of the exit aperture is between 10 and 100. ### Claim 14 (depends on 10) An apparatus as set forth claim 10, further comprising: a vacuum chamber; and a cooling device arranged to chill a surface of the vacuum chamber to condense vapors and fumes therewithin. ### Claim 15 (depends on 13) An apparatus as set forth in claim 13, wherein the cooling device is a Peltier device. ### Claim 16 (depends on 10) An apparatus as set forth in claim 10, further comprising: a skimmer provided at an entrance of the closed source; a sample delivering transfer line spaced from said skimmer at a distance sufficient for reducing flow of carrier gas into said source by at least 5-fold. ### Claim 17 (depends on 16) An apparatus as in claim 16, wherein an excessive carrier gas is pumped down by a differential port of main turbo-pump, which pumps down said time-of-flight mass analyzer. ### Claim 18 (depends on 10) An apparatus as set forth in claim 10, further comprising: means for repulsing ions along the sides of the ion chamber and along the direction of the electron beam. ### Claim 19 (depends on 10) An apparatus as set forth in claim 10, wherein the ion source includes an inner liner and the ion repulsing means includes a ceramic spacer isolating the ion chamber from the inner liner and defines an electrostatic bias and a push-low bias of repeller. ### Claim 20 (depends on 10) An apparatus as set forth in claim 10, wherein the ion source includes an inner liner and an emitter and the repulsing means is defined by positively biased slits disposed between the emitter and the inner liner. ### Claim 21 (depends on 10) An apparatus as set forth in claim 10, wherein the ion source includes an inner liner and an emitter having one or more positively biased slits to confine ions along the beam and to remove secondary ions.