Chromatography-Free Analysis of Mixtures Using a Two-Dimensional Mass Spectrometry (2DMS)-Enabled Quadrupole Time-of-Flight (QToF) Analyzer.

Two-dimensional mass spectrometry (2DMS) is a powerful data-independent analysis (DIA) technique that allows mixtures to be analyzed without chromatographic separation of the components. Until now, high-resolution 2DMS has only been possible using Fourier Transform Ion Cyclotron Resonance (FTICR) instruments, which are impractical for most laboratories. Herein, we present the first experimental demonstration of 2DMS using a quadrupole time-of-flight (QToF) mass spectrometer. These instruments are commonplace, but offer high resolution and the ability to assign peaks in the 2D spectrum based on accurate mass. The key development is the application of stored waveform ion radius modulation (SWIM) to ions trapped in the quadrupole prior to mass analysis by the ToF analyzer. SWIM is an encoding technique that uses broadband dipolar excitation and a radius-dependent fragmentation method to modulate precursor and product ion signals. We show how each component of a peptide mixture can be individually, yet simultaneously, sequenced using collision-induced dissociation (CID) and/or ultraviolet photodissociation (UVPD).