Quadrupole Mass Filter Performance Enhancement Through Use of High Stability Regions

Technology #12716

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schematic diagram of the inventive quadrupole mass filter cross-section
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Inventors
Professor Akintunde Akinwande
Departmentof Electrical Engineering and Computer Science, MIT
External Link (www-mtl.mit.edu)
Luis Fernando Velasquez-Garcia
Microsystems Technology Laboratories, MIT
External Link (www-mtl.mit.edu)
Kerry Cheung
Microsystems Technology Laboratories, MIT
Managed By
Jim Freedman
MIT Technology Licensing Officer - Chemicals, Instruments, Consumer Products
Patent Protection

Performance Enhancement Through Use of Higher Stability Regions and Signal Processing in Non-ideal Quadrupole Mass Filters

US Patent 7,935,923
Publications
Performance Characteristics of a MEMS Quadrupole Mass Filter with Square Electrodes - Experimental and Simulated Results
IEEE Trans. on Instrum. and Measurement, Vol. 59, No. 9, 2010, pp. 2458-2467
Chip-Scale Quadrupole Mass Filters for Portable Mass Spectrometry
Journal of Microelectromechanical Systems, Vol. 19, No. 3, 2010, pp 469-483
An Application of 3D MEMS Packaging: Out-of-Plane Quadrupole Mass Filters
Journal of Microelectromechanical Systems, Vol. 17, No. 6, 2008, pp 1430-1438

The technology presents a method to overcome fabrication defects and enhance the performance of quadrupoles by operating them in regions of high trajectory stability. 

Applications

  • Quadrupole mass filters
  • Mass spectrometry
  • Charged beam manipulation

Problem Addressed

 Quadrupole mass filters are used in mass spectroscopy to separate ions of differing mass-to-charge ratios.  A combination of a DC and an AC voltage applied to the rods generates an oscillating electric field in the interior of the quadrupole that allows transmission of ions traveling through the axial center based on the stability of their trajectories. For a given DC/AC voltage combination, only ions of a certain mass-to-charge ratio are transmitted by the quadrupole; by sweeping a series of DC/AC voltage combinations, the quadrupole can be used with a detector to generate a spectrum, i.e., a series of mass peaks with relative intensity that allows identification of the sample being analyzed. Misalignment of quadruple rods, or other minor defects, reduces the stability of the ionic trajectories and therefore, the accurate separation of these ions. Imperfections such as rod misalignment, misshapen electrodes, and material defects in quadrupole mass filters, arise during manufacturing and to some extent during operation (e.g., misalignment due to differential thermal expansion). Such imperfections limit the achievable resolution of the quadrupole filter and hence its power as an analytic instrument.

Technology

This technology utilizes signal processing to adjust the operational conditions of quadrupole mass filters in order to improve their performance. By operating quadrupoles in high-order stability regions, peak widths are sharpened and the mass spectrum is easier to resolve despite defects caused during the manufacturing process.  Moreover, using drive signal processing, it is possible to create new stability boundaries with high resolution around operating conditions where there are no higher-order resonances.

Advantages

  • Increased resolution of mass spectrum
  • Reduced cost of manufacturing and higher yields by allowing non-ideal devices to operate with high performance as long as electrodes are driven with the correct signals