Electron Impact Ion Source With Fast Response
AssigneeLeco Corporation
InventorAnatoly N. Verenchikov
Life of this patent
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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.
Claims21
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.
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.
Dependencies are inferred from the claim text.