Impact of injection potential on measured ion response for digitally driven mass filters

Abstract

Digital Waveform Technology (DWT) has recently evolved to provide sufficient duty cycle resolution necessary to create a purely digital waveform-based mass filter. Digital operation provides a number of options that remain extremely challenging for sinusoidal waveform technology (SWT) driven systems. One of those options is collecting ions in a gas-filled digital ion guide/trap and subsequently axially injecting the collected ions in a temporally-short and spatially-focused packet into the digital mass filter (DMF). This work explores the effects of trapping ions before mass analysis. In particular, it focusses on the measured response of the ion distribution as a function of axial ejection conditions while maintaining identical trapping conditions. The ejection energy was varied showing changes in the ion distribution that corresponded to desolvation, multimeric dissociation and small molecule from the higher charge states. This study shows that duty cycle-base ion ejection from into an axial potential well and out of the same well of a gas-filled linear quadrupole is essentially equivalent in terms of energy imparted to the ion. However, the energizing mechanism of the ejection process is radial rather than axial. Sampling issues of the trapped ions from the gas-filled quadrupole were analyzed and discussed.