Ultrafast Differential Ion Mobility Spectrometry at Extreme Electric Fields in Multichannel Microchips

Abstract

The maximum electric field intensity (E) in field asymmetric waveform ion mobility spectrometry (FAIMS) analyses was doubled to E > 60 kV/cm. In earlier devices with >0.5 mm gaps, such strong fields cause electrical breakdown for nearly all gases at ambient pressure. As the Paschen curves are sublinear, thinner gaps permit higher E: here, we established 61 kV/cm in N 2 using microchips with 35 μm gaps. As FAIMS efficiency is exceptionally sensitive to E, such values can in theory accelerate analyses at equal resolution by over an order of magnitude. Here we demonstrate FAIMS filtering in ~20 μs or ~1% of the previously needed time, with a resolving power of about half that for "macroscopic" units but sufficing for many applications. Microscopic gaps enable concurrent ion processing in multiple (here, 47) channels, which greatly relaxes the charge capacity constraints of planar FAIMS designs. These chips were integrated with a β-radiation ion source and charge detector. The separation performance is in line with first-principles modeling that accounts for high-field and anisotropic ion diffusion. By extending FAIMS operation into the previously inaccessible field range, the present instrument advances the capabilities for research into ion transport and expands options for separation of hard-to-resolve species.Ion mobility spectrometry (IMS) distinguishes ion species based on transport properties in an inert buffer gas. Conventional or drift tube (DT) IMS that separates ions based on absolute mobility has been used in defense and security applications in the field, such as detection of explosives and chemical warfare agents, since the 1980s. 1 More recently, IMS (combined with mass spectrometry, MS) became topical in structural chemistry and in complex biological and environmental analyses. [1][2][3][4][5][6][7][8][9][10][11] The mobility for any ion-gas pair is a function of the ratio of electric field intensity (E) to the gas number density (N), which can be expressed 2 as a relative deviation (α) from the zero-field mobility K(0) and expanded in infinite series of even powers over E/N:This fact is exploited in differential IMS or field asymmetric waveform IMS (FAIMS) to filter ions by the difference between K at two E/N values. 2,3 A time-dependent electric field E(τ) with alternating segments of high E and low E of opposite polarity (but null mean E) is set up in a gap between two electrodes, through which ions are pulled by gas flow. 2,3 HypotheticalCorrespondence to: Alexandre A. Shvartsburg.

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

“…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].…”

“…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…”

Diagnostic Metabolomic Blood Tests for Endoluminal Gastrointestinal Cancer—A Systematic Review and Assessment of Quality

“…When applied to bio-samples, this analytical process seeks to characterize the closest molecular element to the phenotype in the gene-protein-metabolite cascade (10). High-resolution metabolic snapshots attainable in timeframes of seconds-to-minutes, and tessellation of proven biomarkers to portable nanosensor platforms is often realistic (11)(12)(13). Moreover, being inherently small molecules, metabolites are more likely to be distributed to distant bodily compartments than nucleic acids or proteins, better supporting noninvasive testing (14).…”

FAIMS Biochemical Sensor Based on MEMS Technology

“…In the FAIMS technology of Owlstone, one small space (10 micrometre), short path (depth of a silicon chip) and a muti-channel array type of drift tube structure is used, as shown in figure 4. Compared to the traditional FAIMS structure, the multi-channel can improve the sensitivity; the small space can decrease the radio frequency voltage amplitude needed; the short path can decrease the ion travelling time in the shift tube and increase the analytical efficiency (Shvartsburg et al, 2009). …”