Enhanced Analyte Detection Using In-Source Fragmentation of Field Asymmetric Waveform Ion Mobility Spectrometry-Selected Ions in Combination with Time-of-Flight Mass Spectrometry

Abstract

Miniaturized ultra high field asymmetric waveform ion mobility spectrometry (FAIMS) is used for the selective transmission of differential mobility-selected ions prior to in-source collision-induced dissociation (CID) and time-of-flight mass spectrometry (TOFMS) analysis. The FAIMS-in-source collision induced dissociation-TOFMS (FISCID-MS) method requires only minor modification of the ion source region of the mass spectrometer and is shown to significantly enhance analyte detection in complex mixtures. Improved mass measurement accuracy and simplified product ion mass spectra were observed following FAIMS preselection and subsequent in-source CID of ions derived from pharmaceutical excipients, sufficiently close in m/z (17.7 ppm mass difference) that they could not be resolved by TOFMS alone. The FISCID-MS approach is also demonstrated for the qualitative and quantitative analysis of mixtures of peptides with FAIMS used to filter out unrelated precursor ions thereby simplifying the resulting product ion mass spectra. Liquid chromatography combined with FISCID-MS was applied to the analysis of coeluting model peptides and tryptic peptides derived from human plasma proteins, allowing precursor ion selection and CID to yield product ion data suitable for peptide identification via database searching. The potential of FISCID-MS for the quantitative determination of a model peptide spiked into human plasma in the range of 0.45-9.0 μg/mL is demonstrated, showing good reproducibility (%RSD < 14.6%) and linearity (R(2) > 0.99).

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

“…Figure 2b, black dotted line, is also centred around CF 0.65 Td at DF 200 Td, showing a strong correlation to the secondary peak in the CF spectra of the 3-MX monomer. This suggests that the dimer was transmitted through the FAIMS electrodes intact and fragmented in the MS interface by in-source collision induced dissociation (in-source CID) at 150 V post-FAIMS separation, resulting in the two peaks evident in the CF spectra and the FAIMS heat maps for the m/z 189.04 [36,40]. This is further supported by the mass spectra (Supplementary Figure 1) extracted at the optimum FAIMS transmission conditions for the two peaks (DF 200 Td, CF -0.05 Td and 0.65 Td) at each of the three fragmentor voltages, showing the m/z 189 ion of the 3-MX monomer present in the mass spectra at CF 0.65 Td at 150 V, which decreases at 100 V and is not present at 50 V. In each of the heat maps for the 3-MX monomer (Figure 2b, c, and d), the intensity reduces sharply as the DF increases above 240 Td, resulting from a greater number and velocity of collisions due to field heating at higher DFs [28,32].…”

“…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.…”

Detection, Identification, and Occurrence of Thiotetronic Acids in Drinking Water from Underground Sources by Electrospray Ionization-High Field Asymmetric Waveform Ion Mobility Spectrometry-Quadrupole Time-of-Flight-Mass Spectrometry

“…Figure 3 shows MS/MS spectra from ESI-FAIMS-MS/MS analysis of the major sulfur containing compound (m/z 203) which was detected in groundwater at CV = 12.5 V. The m/z 203 precursor generates several products at m/z 221, 179, 161, 143, 119, 101, and 83, and each product ion was additionally investigated in the pseudo MS 3 mode by inducing the source fragmentation of the precursor ion separated by FAIMS at CV = 12.5 V. Turning a QTOF with MS/MS capability into a pseudo MS 3 instrument with MS/MS/MS capability would not be possible without FAIMS due to the abundant chemical background from groundwater and ESI. 26 At minimal ion activation conditions in CID (CE = 4 V in Figure 3A), the m/z 203 ion forms the water adduct at m/z 221. As shown in Scheme 1, this ion/H 2 O reaction results from TA ring cleavage and involves an extremely reactive ketene group with an electron deficiency at the positively polarized middle carbon atom.…”

Analyzing complex mixtures of drug-like molecules: Ion mobility as an adjunct to existing liquid chromatography-(tandem) mass spectrometry methods

“…Recently IM-MS/MS has been used to enhance peptide detection [41], study the fragmentation patterns of drug metabolites [42] and (de-)protomers [24][25][26]43,44].…”