A multichannel phase-locked waveform generator for a rotating electric field mass analyzer

Abstract

We have developed a multichannel phase-locked sine waveform generator for a mass dispersive rotating electric field device, known as a rotating wall mass analyzer (RWMA). The waveform generator outputs eight sine waves phase shifted by 45°. The frequency of the waveforms is adjustable in the range of 0.1–100 kHz and the maximum amplitude is 100 Vp-p, which is greater than 20 Vp-p provided by commercial arbitrary waveform generators. Adjustment of either amplitude or frequency maintains phase alignment for all eight output channels to continually generate a uniform rotating electric field inside the RWMA. The RWMA is a high-throughput mass analyzer for preparative mass spectrometry that separates a multicomponent continuous ion beam in space and enables the deposition of ions of different m/z onto concentric ring shapes on surfaces. Here, we demonstrate that increasing the generator's amplitude from 20 Vp-p to 50 Vp-p resolves a continuous ion beam of ubiquitin charge states with a measured mass resolution (m/Δm) of R = 14. This resolution improves to R = 26 for a 100 Vp-p generator output. Furthermore, the designed waveform generator facilitates a single m/z calibration of the rotating electric field parameters to extract a m/z value from a measured radius. These parameters are shown to be valid for other m/z species, ion beam kinetic energies, and ionization polarity modes.