Chemistry Proposal Defense Seminar – Sumeet Chakravorty

About the event

Speaker: Sumeet Chakravorty

Group: Reilly

Title: Experimental Analysis of Transmission and Resolving Capabilities of Digitally Operated Quadrupole Mass Filters

Abstract: Quadrupole mass filters and guides are integral components in many mass spectrometers. These mass filters are typically operated with sinusoidal waveforms applied to the electrodes with opposing electrodes electrically connected and each pair receiving rf potentials that are 180° out of phase from each other. By applying a DC and rf potential, it is possible to narrow the range of stable masses, the stable mass window can be further narrowed by changing the ratio of DC to rf potential and an effective mass filter can be created by ramping both voltages at fixed frequency. Opposing the conventional technique, mass filters operated with digitally produced waveforms with the frequency varied and the rf and DC potentials fixed can create stable mass windows of variable width by changing the duty cycle of the rf waveform on both electrode pairs without applying a static DC potential between the rods. In most analytical techniques, such as the sine driven mass filter, resolution comes at the cost of transmission or signal intensity. The main advantage of changing the duty cycle is the ability to access narrower stable mass windows in higher order Mathieu space stability zones without the cost of transmission of ions through the mass filter. This project will experimentally explore the capabilities of digitally operated quadrupole mass filters in their capacity to achieve high resolution and transmission of ions by changing duty cycle and AC voltage. In addition, another important objective of this project is to understand the limitations of higher order stability zones as a function of geometric and operating parameters. This insight into the capacity and limitations of higher order stability zones for digitally operated quadrupole mass filters will provide a basis for future techniques and instrumentation methods that rival current and typically sinusoidally operated quadrupole techniques.