Experimental Evaluation of Higher Order Stability Zones Using a Digitally Operated Quadrupole Mass Filter.

Recent improvements to the comparison-based method of digital waveform generation increased the reproducibility of the waveforms so that the higher-order Mathieu stability zones can be accessed reliably. Digitally driven quadrupole mass filters access these zones using a fixed AC voltage and rectangular waveforms that are defined by a duty cycle. In this context, the duty cycle is the fraction of the waveform period where the waveform remains in the high state.

Experimental Validation of the Digital Tandem Mass Filter.

This work presents the experimental evaluation of a digital tandem mass filter that is composed of two digitally operated low-resolution mass filters in series whose mass windows are shifted with respect to each other. The overlap of the mass windows allows the resolution (Δ) of ions to be narrowed to provide better resolving power, while the acceptance of the tandem mass filter is defined by the acceptance of the first low-resolution quadrupole. Our experiments show that digital operation fulfills the promise of the tandem mass filter for providing better ion transmission at the same or better resolving power as a single quadrupole mass filter.

Effect of Jitter on Digital Mass Filter Analysis in Higher Stability Zones.

Waveform reproducibility is a critical factor for performing high resolution mass analysis with digitally operated quadrupole mass filters and traps operating in higher stability zones. In this work, Hill equation-based stability calculations were used to define the effect of period jitter on mass analysis in higher stability zones. These calculations correlate well with experimental observations in higher stability zones.