Chemistry Dissertation Defense – Elizabeth Groetsema

About the event

Speaker: Elizabeth Groetsema

Group: Dr. Brian Clowers

Title: APPLICATIONS OF DIGITALLY DRIVEN QUADRUPOLES OPERATING IN HIGHER-ORDER MATHIEU SPACE STABILITY ZONES IN MODIFIED COMMERCIAL MASS SPECTROMETERS

Abstract:

Quadrupoles are utilized in many mass spectrometry instrument designs for their versatility as ion guides, mass filters, and mass analyzers. Quadrupoles are comprised of four metal rods with applied AC and DC potentials that facilitate ion stability within them. Conventional quadrupole systems employ a fixed-frequency sinusoidal RF waveform and analyze ions by scanning both the AC and DC potentials. This method leads to limitations in mass range and resolving power. Digital quadrupoles, in contrast, leverage a fixed-potential rectangular RF waveform and scan frequency. Scanning through frequency removes mass range limitations, enabling analysis of large biomolecules. Additionally, changing the duty-cycle of the RF waveform, the percentage of the waveform in the high state, manipulates ion stability and allows access to higher-order Mathieu space stability zones without the need for a DC potential. Operating in higher-order Mathieu space stability zones yields higher resolving power compared to conventional operation, ensuring better separation of ions and improved data integrity. In this work, two commercial mass spectrometers, a quadrupole time-of-flight instrument and a triple quadrupole instrument, were modified for digital operation of the filtering and/or analyzing quadrupoles to leverage the advantages of higher resolving power and extended mass range. This work furthers the versatility of quadrupole instruments by demonstrating the feasibility of widespread adoption of digitally driven systems and the range of applications where they can deliver innovative benefits.