High-definition differential ion mobility spectrometry with resolving power up to 500

Abstract

As the resolution of analytical methods improves, further progress tends to be increasingly limited by instrumental parameter instabilities that were previously inconsequential. This is now the case with differential ion mobility spectrometry (FAIMS), where fluctuations of the voltages and gas pressure have become critical. A new high-definition generator for FAIMS compensation voltage reported here provides a stable and accurate output than can be scanned with negligible steps. This reduces the spectral drift and peak width, thus improving the resolving power (R) and resolution. The gain for multiply-charged peptides that have narrowest peaks is up to ~40%, and R ~400-500 is achievable using He/N(2) or H(2)/N(2) gas mixtures.

Fig. 1

Oscilloscope traces for CV output from the generator over 60 s with the previous (left panel) and present (right panel) systems. A version including the data with finer time resolution is shown in Fig. S1.

Fig. 2

Measurements for Syntide 2 (3+ ion): (a) full spectrum, (b) a window around the peak II, (c) a run of 20 consecutive replicate windows, each scanned in 75 s. Four runs with 66 windows total are shown in Fig. S2. Temporal variation of the signal seen here is typical for low-intensity ion fluxes from ESI [15].

Fig. 3

Measured E_C values for Syntide 2 with z = 3 and 4 in H₂/N₂ gas mixtures.

Fig. 4

Normalized FAIMS spectra for two monomethylated localization variants of H3 tail (color-coded) with z = 5 and 6, measured using H₂/N₂ with 75% and 80% H₂ (v/v), as labeled. Peaks for different conformers are marked by letters, following ref. [16]. The widths (w, V/cm) are shown for the well-shaped peaks.

Fig. 5

FAIMS spectra for the K4Me/K9Me mixture, measured for 6+ ions using H₂/N₂ with 75% or 80% H₂, as labeled. Vertically scaled spectra for the components are overlaid.