Quadrupole Mass Filter Performance Enhancement Through Use of High Stability Regions

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