Miniaturized Ultra High Field Asymmetric Waveform Ion Mobility Spectrometry Combined with Mass Spectrometry for Peptide Analysis

Abstract

Miniaturized ultra high field asymmetric waveform ion mobility spectrometry (ultra-FAIMS) combined with mass spectrometry (MS) has been applied to the analysis of standard and tryptic peptides, derived from α-1-acid glycoprotein, using electrospray and nanoelectrospray ion sources. Singly and multiply charged peptide ions were separated in the gas phase using ultra-FAIMS and detected by ion trap and time-of-flight MS. The small compensation voltage (CV) window for the transmission of singly charged ions demonstrates the ability of ultra-FAIMS-MS to generate pseudo-peptide mass fingerprints that may be used to simplify spectra and identify proteins by database searching. Multiply charged ions required a higher CV for transmission, and ions with different amino acid sequences may be separated on the basis of their differential ion mobility. A partial separation of conformers was also observed for the doubly charged ion of bradykinin. Selection on the basis of charge state and differential mobility prior to tandem mass spectrometry facilitates peptide and protein identification by allowing precursor ions to be identified with greater selectivity, thus reducing spectral complexity and enhancing MS detection.

Analysis of Supramolecular Complexes of 3-Methylxanthine with Field Asymmetric Waveform Ion Mobility Spectrometry Combined with Mass Spectrometry

“…ESI-FAIMS-MS analyses were carried out using an Agilent 6230 TOF MS (Agilent Technologies, UK) fitted with a prototype miniaturised chip-based FAIMS (Owlstone Ltd., Cambridge, UK), which has been described in detail elsewhere [33,36,37]. The FAIMS device was located behind the modified spray shield of the Jet Stream ESI source, in front of the mass spectrometer inlet capillary, and consists of multiple parallel planar electrode channels (100 μm electrode gap) with a short trench length (78.1 mm) and ion path length (700 μm).…”

“…However, ESI-FAIMS-MS allows for the separation of ions based upon compound-dependent differences in high and low field mobility as a result of charge state [33,36,41]. FAIMS separation may therefore be used to suppress or enhance the transmission of singly or multiply charged ions selectively.…”

“…In a FAIMS device, ions pass between two electrodes with an applied asymmetric RF waveform known as the dispersion field (DF), under which the ions experience alternating low and high fields, resulting in a net displacement towards one of the electrodes [27][28][29][30][31]. A small DC voltage, known as the compensation field (CF), is superimposed on the DF to transmit selected analytes by offsetting the net displacement through the device [32][33][34] The DF and CF [unit of Townsend (Td) where 1 Td = 10 -17 V cm…”

Comparison of the peak capacity for DMS filters with various gap height: experimental and simulations results

“…The effective gap improved significantly when the frequency increased to 30 MHz, or the spacing of the DMS electrodes increased. Commercial DMS devices from Owlstone have a very narrow gap height and operate in the high frequency regime [14][15][16]. Experiments were conducted with 10 peptides from a BSA digest, to further determine if high separation fields could compensate for limited gap height.…”

“…The spacing between the parallel plates in a DMS analyzer can be generally referred to as the gap height (h). The literature contains examples of numerous atmospheric pressure DMS devices that include gap heights ranging from approximately 35 μm [14][15][16] to 2 mm [17,18]. Three of these publications have attempted to compare the separation capability of devices with different gap heights.…”