Behaviour of tetraalkylammonium ions in high‐field asymmetric waveform ion mobility spectrometry

Abstract

High-field asymmetric waveform ion mobility spectrometry (FAIMS) is an ion-filtering technique recently adapted for use with liquid chromatography/mass spectrometry (LC/MS) to remove interferences during analysis of complex matrices. This is the first systematic study of a series of singly charged tetraalkylammonium ions by FAIMS-MS. The compensation voltage (CV) is the DC offset of the waveform which permits the ion to emerge from FAIMS and it was determined for each member of the series under various conditions. The electrospray ionization conditions explored included spray voltage, vaporizer temperature, and sheath and auxiliary gas pressure. The FAIMS conditions explored included carrier gas flow rate, electrode temperature and composition of the carrier gas. Optimum desolvation was achieved using sufficient carrier gas (flow rate > or = 2 L/min) to ensure stable response. Low-mass ions (m/z 100-200) are more susceptible to changes in electrode temperature and gas composition than high mass ions (m/z 200-700). As a result of this study, ions are reliably analyzed using standard FAIMS conditions (dispersion voltage -5000 V, carrier gas flow rate 3 L/min, 50% helium/50%nitrogen, inner electrode temperature 70 degrees C and outer electrode temperature 90 degrees C). Variation of FAIMS conditions may be of great use for the separation of very low mass tetraalkylammonium (TAA) ions from other TAA ions. The FAIMS conditions do not appear to have a major effect on higher mass ions.

Predicting Compensation Voltage for Singly-charged Ions in High-Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS)

“…The slope of the ΔCV versus m/z curve is greatest at low m/z values, which indicates that the smaller ions will exhibit greater response to the gas composition change than larger ones. This behavior was described for homologous series of TAA ions [14].…”

“…In contrast, great differences in FAIMS behavior were observed for small and large TAA homologues. The behavior of TAA ions has been studied previously in some detail [14].…”

“…Combined solutions of the TAAs were prepared by mixing individual TAA solutions. The FAIMS/MS analysis is described in detail elsewhere [14]. All the experiments were conducted using direct ESI infusion at 5 μL/min flow rate.…”

Conformational Distribution of Bradykinin [bk + 2 H]2+ Revealed by Cold Ion Spectroscopy Coupled with FAIMS

“…The FAIMS device that we use is of transverse cylindrical geometry ("side-to-side," Thermo Scientific) [20][21][22]. The process of ion separation in FAIMS has been described in detail elsewhere [2,3,23].…”

Elimination of the helium requirement in high‐field asymmetric waveform ion mobility spectrometry (FAIMS): beneficial effects of decreasing the analyzer gap width on peptide analysis

“…On a system dedicated to FAIMS, this pressure can be adjusted on installation but is not easy to vary upon daily (or regular) installation and removal of the FAIMS electrode interface. The use of helium also imparts a minimum requirement on the curtain gas flow rate to ensure that the 'carrier gas' (i.e., separation gas) is not diluted by atmospheric gas being pulled into the mass spectrometer …”