{
"id": "ep9q1ggcc2",
"slug": "ion-mobility-separation",
"title": "Ion mobility separation",
"updated": "2026-10-25",
"topic_path": [
{
"id": "physical",
"label": "Physical world and mathematics",
"api_url": "https://www.edgepedia.org/api/v1/topics/physical"
},
{
"id": "physical.chemistry",
"label": "Chemistry",
"api_url": "https://www.edgepedia.org/api/v1/topics/physical.chemistry"
},
{
"id": "physical.chemistry.methods",
"label": "Chemical principles and methods",
"api_url": "https://www.edgepedia.org/api/v1/topics/physical.chemistry.methods"
},
{
"id": "physical.chemistry.methods.analytical-chemistry",
"label": "Analytical chemistry",
"api_url": "https://www.edgepedia.org/api/v1/topics/physical.chemistry.methods.analytical-chemistry"
},
{
"id": "physical.chemistry.methods.analytical-chemistry.electrophoresis-and-ion-mobility",
"label": "Electrophoresis and ion mobility",
"api_url": "https://www.edgepedia.org/api/v1/topics/physical.chemistry.methods.analytical-chemistry.electrophoresis-and-ion-mobility"
}
],
"geo": [
{
"id": "geo.nongeo.t1800.physical.chemistry.methods.analytical-chemistry",
"label": "Non-geographic · 1800 to 1945: Analytical chemistry",
"api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1800.physical.chemistry.methods.analytical-chemistry",
"path": [
{
"id": "geo.nongeo",
"label": "Non-geographic",
"api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo"
},
{
"id": "geo.nongeo.t1800",
"label": "Non-geographic · 1800 to 1945",
"api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1800"
},
{
"id": "geo.nongeo.t1800.physical",
"label": "Physical world and mathematics",
"api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1800.physical"
},
{
"id": "geo.nongeo.t1800.physical.chemistry",
"label": "Chemistry",
"api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1800.physical.chemistry"
},
{
"id": "geo.nongeo.t1800.physical.chemistry.methods",
"label": "Chemical principles and methods",
"api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1800.physical.chemistry.methods"
},
{
"id": "geo.nongeo.t1800.physical.chemistry.methods.analytical-chemistry",
"label": "Analytical chemistry",
"api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1800.physical.chemistry.methods.analytical-chemistry"
}
]
},
{
"id": "geo.nongeo.t1946.physical.chemistry.methods.analytical-chemistry",
"label": "Non-geographic · 1946 to 2000: Analytical chemistry",
"api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.physical.chemistry.methods.analytical-chemistry",
"path": [
{
"id": "geo.nongeo",
"label": "Non-geographic",
"api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo"
},
{
"id": "geo.nongeo.t1946",
"label": "Non-geographic · 1946 to 2000",
"api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946"
},
{
"id": "geo.nongeo.t1946.physical",
"label": "Physical world and mathematics",
"api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.physical"
},
{
"id": "geo.nongeo.t1946.physical.chemistry",
"label": "Chemistry",
"api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.physical.chemistry"
},
{
"id": "geo.nongeo.t1946.physical.chemistry.methods",
"label": "Chemical principles and methods",
"api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.physical.chemistry.methods"
},
{
"id": "geo.nongeo.t1946.physical.chemistry.methods.analytical-chemistry",
"label": "Analytical chemistry",
"api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.physical.chemistry.methods.analytical-chemistry"
}
]
}
],
"excerpt": "Ion mobility separation, also known as ion mobility spectrometry (IMS), is a mass spectrometry technique that separates gas-phase ions by size and shape, and is used in laboratories and portable detectors for explosives.",
"snippet": "Ion mobility separation, also known as ion mobility spectrometry (IMS), is a mass spectrometry technique that separates gas-phase ions by size and shape, and is used in laboratories and portable detectors for explosives.",
"node": "physical.chemistry.methods.analytical-chemistry.electrophoresis-and-ion-mobility",
"markdown": "# Ion mobility separation\n\nIon mobility separation (ion mobility spectrometry, IMS) is a mass spectrometry technique that separates gas-phase ions by how fast they drift through a buffer gas under an electric field, adding a shape- and size-based dimension to the mass-to-charge information from the mass analyzer. Where liquid chromatography separates by lipophilicity and mass spectrometry by mass and charge, IMS separates by an ion's size-to-charge ratio, and the measured drift time converts directly into a collision cross section (CCS), a molecular property that can be compared against reference values.[1](https://www.mdpi.com/2297-8739/8/3/33) The technique is used both as a standalone detector and hyphenated to LC-MS, and portable IMS units are standard tools for field detection of hazardous compounds.[2](https://par.nsf.gov/servlets/purl/10423670)\n\n| Key fact | Detail |\n|---|---|\n| Measured quantity | Drift time \\( t_{D} \\) over a separation length \\( L \\), giving mobility \\( K = v_{D}/E \\)[2](https://par.nsf.gov/servlets/purl/10423670) |\n| Cross section | In the low-field limit, CCS follows the Mason–Schamp equation from \\( K \\)[2](https://par.nsf.gov/servlets/purl/10423670) |\n| Standardization | Reduced mobility \\( K_{0} = K \\cdot (N/N_{0}) \\) allows comparison across pressures and temperatures[3](https://www.sciencedirect.com/science/article/abs/pii/S1367593117301229) |\n| CCS determination | DTIMS gives CCS from first principles; TWIMS and TIMS require calibration with reference compounds[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10037255/) |\n| Resolving power | Commercial DTIMS ~50–60 and TWIMS ~30–40; TIMS up to roughly 400; SLIM platforms exceed 1500[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10037255/) • [5](https://par.nsf.gov/servlets/purl/10128613) • [6](https://pmc.ncbi.nlm.nih.gov/articles/PMC11785821/) |\n| CCS precision | DTIMS 0.29% RSD (interlaboratory); TIMS <0.2% RSD and ~2% agreement with DTIMS[7](https://www.intechopen.com/chapters/1156601) • [5](https://par.nsf.gov/servlets/purl/10128613) |\n| Reference data | The METLIN-CCS database holds over 185,000 CCS values from more than 27,000 molecular standards[8](https://doi.org/10.1038/s41592-023-02078-5) |\n\n## How it works\n\nIons pulled through a buffer gas by an electric field \\( E \\) reach a constant drift velocity \\( v_{D} \\) set by the balance between field acceleration and momentum loss in collisions with gas molecules. The ion mobility is their ratio, \\( K = v_{D}/E \\), and is obtained experimentally from the drift time \\( t_{D} \\) and the length \\( L \\) of the separation region.[2](https://par.nsf.gov/servlets/purl/10423670) Because mobility depends on how much surface the ion presents to the gas, \\( K \\) reports on molecular shape and size, not only mass.\n\nIn the low-field limit, where \\( E/N \\) is low enough that the drift velocity stays far below thermal velocities, mobility converts to the collision cross section \\( \\Omega \\) through the Mason–Schamp equation:\n\n\\[ \\Omega = \\frac{3ze}{16N}\\left(\\frac{2\\pi}{\\mu k_{B}T}\\right)^{1/2}\\frac{1}{K} \\]\n\nwhere \\( z \\) is the charge state, \\( N \\) the drift-gas number density, \\( \\mu \\) the reduced mass of the ion–gas pair, \\( k_{B} \\) the [Boltzmann constant](https://www.edgepedia.org/boltzmann-constant), and \\( T \\) the gas temperature.[2](https://par.nsf.gov/servlets/purl/10423670) To compare experiments done at different pressures and temperatures, mobility is reduced to standard conditions, \\( K_{0} = K \\cdot (N/N_{0}) = K \\cdot (p/p_{0}) \\cdot (T_{0}/T) \\), with \\( N_{0} = 2.687 \\times 10^{25} \\ \\mathrm{m^{-3}} \\), \\( p_{0} = 760 \\ \\mathrm{Torr} \\), and \\( T_{0} = 273.16 \\ \\mathrm{K} \\).[3](https://www.sciencedirect.com/science/article/abs/pii/S1367593117301229)\n\nTwo qualifications matter for interpretation. The mobility-derived \\( \\Omega \\) is strictly a momentum-transfer collision integral, which can differ from a purely geometric collision cross section by up to a factor of 1.4.[9](https://pubmed.ncbi.nlm.nih.gov/30707468/) Separation quality is described by the single-peak resolving power \\( R_{m} = t_{d}/\\Delta t_{d} \\), the drift time divided by the full peak width at half maximum.[10](https://pubs.rsc.org/en/content/articlepdf/2015/an/c5an00923e)\n\n## How it is done\n\nAll IMS-MS experiments share the same sequence: ions are formed (commonly by electrospray), transferred into a gas-filled separation region, separated by mobility, and delivered to a mass analyzer. The details differ by analyzer type.\n\nIn **drift-tube IMS (DTIMS)**, ions drift through a uniform weak field; drift tubes span 5 cm to 3 m or more, operated at fields of roughly 5–100 V/cm.[11](https://gala.gre.ac.uk/id/eprint/9541/1/%28item_9541%29_LAPTHORN_PULLEN_CHOWDHRY_authorarchive_PAPER1_Jul03_2012.pdf) Measuring drift times at several field strengths and extrapolating against inverse voltage yields CCS from first principles, without calibrants.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10037255/)\n\nIn **traveling-wave IMS (TWIMS)**, pulsed DC waves with velocities in the hundreds of m/s and amplitudes of tens of volts push ions through the cell; CCS requires calibration with standards of known CCS, typically via a log-log fit.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC11785821/) • [4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10037255/)\n\nIn **trapped IMS (TIMS)**, a directional gas flow propels ions against an opposing electric-field gradient of roughly 70 V/cm in a compact 5–10 cm cell; ions are eluted by scanning the field downward, in order of decreasing \\( K \\), giving resolving powers of roughly 200–400 \\( K/\\Delta K \\).[12](https://link.springer.com/content/pdf/10.1007/s13361-019-02288-2.pdf) • [2](https://par.nsf.gov/servlets/purl/10423670)\n\n**FAIMS and differential-mobility analyzers** separate continuously by applying an asymmetric high-field waveform and scanning a compensation voltage; they filter rather than disperse ions in time and do not readily yield CCS values.[11](https://gala.gre.ac.uk/id/eprint/9541/1/%28item_9541%29_LAPTHORN_PULLEN_CHOWDHRY_authorarchive_PAPER1_Jul03_2012.pdf) • [4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10037255/)\n\n## Origin\n\nMeasurements of ions drifting through gases under electric fields predate mass spectrometry itself, and both techniques trace their early development to the [Cavendish Laboratory](https://www.edgepedia.org/cavendish-laboratory).[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10037255/) The modern platform variants are each anchored by dedicated fundamental treatments. The fundamentals of traveling-wave IMS were analyzed in detail by Alexandre A. Shvartsburg and Richard D. Smith in Analytical Chemistry in 2008.[13](https://doi.org/10.1021/ac8016295) The fundamentals of trapped ion mobility spectrometry were set out by Karsten Michelmann and colleagues in 2014.[14](https://doi.org/10.1007/s13361-014-0999-4) The serpentine ultralong path with extended routing (SUPER) high-resolution traveling-wave IM-MS, built on structures for lossless ion manipulations (SLIM), was reported by Liulin Deng and colleagues in Analytical Chemistry in 2017.[15](https://doi.org/10.1021/acs.analchem.7b00185) A cyclic ion mobility–mass spectrometry system was reported by Kevin Giles and colleagues in Analytical Chemistry in 2019.[16](https://doi.org/10.1021/acs.analchem.9b01838) Tandem trapped ion mobility spectrometry (tTIMS/MS) was reported by Fanny C. Liu and colleagues in [The Analyst](https://www.edgepedia.org/the-analyst) in 2022.[17](https://doi.org/10.1039/d2an00335j) The METLIN-CCS reference database was reported by Erin S. Baker and colleagues in [Nature Methods](https://www.edgepedia.org/nature-methods) in 2023.[8](https://doi.org/10.1038/s41592-023-02078-5)\n\n## Variants\n\nIMS analyzers classify into time-dispersive designs (DTIMS, TWIMS), space-dispersive designs (FAIMS, DMA), and trapping designs with selective release (TIMS).[1](https://www.mdpi.com/2297-8739/8/3/33) Because TWIMS needs only modest voltages, the geometry can be extended to extremely long paths: the Waters cyclic IM device uses a 98-cm ring that supports multipass separations and mobility-based selection, and MOBion Systems offers a 13-m TW-SLIM module aimed at replacing some LC-MS separations with faster mobility separations.[2](https://par.nsf.gov/servlets/purl/10423670) SLIM boards can be routed in serpentine, effectively kilometer-scale paths.[15](https://doi.org/10.1021/acs.analchem.7b00185) Tandem TIMS places two trapping cells in series, allowing mobility-based selection before fragmentation for heterogeneous samples.[17](https://doi.org/10.1039/d2an00335j)\n\n## Applications\n\nIMS-MS serves two broad families of use. In the laboratory, it adds a shape-based separation to proteomics, metabolomics, lipidomics, and structural biology: TIMS with convex electrodes has measured CCS up to 23,000 Ų with <0.2% RSD across m/z up to 19,000 for near-megadalton assemblies, and the timsTOF with PASEF achieves a near-100% duty cycle by parallel accumulation with serial fragmentation.[5](https://par.nsf.gov/servlets/purl/10128613) In the field, portable IMS devices are routinely used for explosives and chemical-warfare-agent detection at airports and in military operations.[12](https://link.springer.com/content/pdf/10.1007/s13361-019-02288-2.pdf)\n\nCoupled to LC-MS, mobility adds peak capacity and identification confidence by filtering isobaric interferences and providing an extra measured property (CCS) for each feature. In a food-analysis example, adding drift-time selection to a TWIMS LC-MS method raised the signal-to-noise ratio of an analyte in animal feed extract by 12%, from 68 to 76.[18](https://www.chromatographyonline.com/view/ion-mobility-mass-spectrometry-food-analysis-update) Higher-resolution platforms expose structure that routine instruments miss: SLIM IM-MS with resolving power above 200 revealed 5–50% more CCS-aligned lipid features than DTIM-MS across seven lipid subclass extracts.[19](https://www.osti.gov/pages/biblio/2377775)\n\n## Limitations and alternatives\n\nThe Mason–Schamp conversion is valid only in the low-field limit. In TWIMS the drift velocity can approach the thermal velocity (for example \\( v_{T} \\) of 1239 m/s in helium and 495 m/s in nitrogen at 300 K for \\( m = 200 \\)), so the equation is not necessarily valid there and the measured quantity is a momentum-transfer collision integral.[20](https://arxiv.org/pdf/1709.02953) • [9](https://pubmed.ncbi.nlm.nih.gov/30707468/) Stepped-field DTIMS \\( K_{0} \\) values determined from first principles are treated as primary standards, while TWIMS and TIMS values rest on calibration functions built from reference compounds.[9](https://pubmed.ncbi.nlm.nih.gov/30707468/) TWIMS calibration is not universal: results depend on the calibrant, which should match the analyte in size, charge, and chemical class, and using peptide calibrants for lipid analyses has demonstrated significant error.[7](https://www.intechopen.com/chapters/1156601) Practical failure modes include ion lapping or wrap-around in multipass cells, which a velocity-based calibration was designed to address.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC11785821/) [Duty cycle](https://www.edgepedia.org/duty-cycle) is another constraint: pulsed DTIMS transmits only about 0.1–1% of generated ions to the drift tube, and Hadamard multiplexing can raise the duty cycle to as high as 50%.[7](https://www.intechopen.com/chapters/1156601)\n\nCompared with LC-MS alone, IMS adds an orthogonal, rapidly recorded separation dimension and a CCS observable, at the cost of calibration dependencies and duty-cycle losses. Machine-learning CCS prediction is an active complement to measurement, with tools including AllCCS, CCSbase, CCSP 2.0, DeepCCS, and SigmaCCS2.[21](https://pubs.acs.org/jcisd8/article/doi/10.1021/acs.jcim.6c00371/5425701/Deep3DCCS-Geometry-Driven-Collision-Cross-Section) Since 2023, the notable changes are the maturation of commercial high-resolution SLIM platforms such as MOBIE,[22](https://pubs.acs.org/doi/abs/10.1021/jasms.5c00056) the METLIN-CCS reference database,[8](https://doi.org/10.1038/s41592-023-02078-5) and machine-learning CCS prediction including pretrained-model approaches.[23](https://www.nature.com/articles/s42004-025-01540-z)\n\n## References\n\n1. [Ion Mobility–Mass Spectrometry for Bioanalysis](https://www.mdpi.com/2297-8739/8/3/33)\n2. [Ion Mobility Spectrometry (review, NSF PAR copy)](https://par.nsf.gov/servlets/purl/10423670)\n3. [Fundamentals of ion mobility spectrometry (Gabelica & Marklund, Curr Opin Chem Biol)](https://www.sciencedirect.com/science/article/abs/pii/S1367593117301229)\n4. [Ion Mobility Mass Spectrometry for Structural Biology: Insights Gained by Measuring Mass, Charge, and Collision Cross Section](https://pmc.ncbi.nlm.nih.gov/articles/PMC10037255/)\n5. [Trapped Ion Mobility Spectrometry (TIMS) review](https://par.nsf.gov/servlets/purl/10128613)\n6. [Recent advances in high-resolution traveling wave-based ion mobility separations coupled to mass spectrometry](https://pmc.ncbi.nlm.nih.gov/articles/PMC11785821/)\n7. [Ion Mobility Mass Spectrometry: Instrumentation and Applications (IntechOpen chapter)](https://www.intechopen.com/chapters/1156601)\n8. [Erin S. Baker and colleagues (2023). METLIN-CCS: an ion mobility spectrometry collision cross section database. Nature Methods.](https://doi.org/10.1038/s41592-023-02078-5)\n9. [Recommendations for reporting ion mobility Mass Spectrometry measurements](https://pubmed.ncbi.nlm.nih.gov/30707468/)\n10. [Resolving power theories for ion mobility spectrometry (Analyst)](https://pubs.rsc.org/en/content/articlepdf/2015/an/c5an00923e)\n11. [(item 9541) LAPTHORN PULLEN CHOWDHRY authorarchive PAPER1 Jul03 2012 (gala.gre.ac.uk)](https://gala.gre.ac.uk/id/eprint/9541/1/%28item_9541%29_LAPTHORN_PULLEN_CHOWDHRY_authorarchive_PAPER1_Jul03_2012.pdf)\n12. [Ion Mobility Spectrometry: Fundamental Concepts, Instrumentation, Applications (JASMS 2019)](https://link.springer.com/content/pdf/10.1007/s13361-019-02288-2.pdf)\n13. [Alexandre A. Shvartsburg, Richard D. Smith (2008). Fundamentals of Traveling Wave Ion Mobility Spectrometry. Analytical Chemistry.](https://doi.org/10.1021/ac8016295)\n14. [Karsten Michelmann and colleagues (2014). Fundamentals of Trapped Ion Mobility Spectrometry. Journal of the American Society for Mass Spectrometry.](https://doi.org/10.1007/s13361-014-0999-4)\n15. [Liulin Deng and colleagues (2017). Serpentine Ultralong Path with Extended Routing (SUPER) High Resolution Traveling Wave Ion Mobility-MS using Structures for Lossless Ion Manipulations. Analytical Chemistry.](https://doi.org/10.1021/acs.analchem.7b00185)\n16. [Kevin Giles and colleagues (2019). A Cyclic Ion Mobility-Mass Spectrometry System. Analytical Chemistry.](https://doi.org/10.1021/acs.analchem.9b01838)\n17. [Fanny C. Liu and colleagues (2022). Tandem-trapped ion mobility spectrometry/mass spectrometry ( t TIMS/MS): a promising analytical method for investigating heterogenous samples. The Analyst.](https://doi.org/10.1039/d2an00335j)\n18. [Ion Mobility–Mass Spectrometry for Food Analysis: An Update](https://www.chromatographyonline.com/view/ion-mobility-mass-spectrometry-food-analysis-update)\n19. [High-resolution ion mobility based on traveling wave SLIM resolves hidden lipid features](https://www.osti.gov/pages/biblio/2377775)\n20. [Fundamentals of ion mobility spectrometry (Gabelica, Shvartsburg et al., preprint copy)](https://arxiv.org/pdf/1709.02953)\n21. [Deep3DCCS: Geometry-Driven Collision Cross Section Prediction from Multi-View Molecular Projection Tensors](https://pubs.acs.org/jcisd8/article/doi/10.1021/acs.jcim.6c00371/5425701/Deep3DCCS-Geometry-Driven-Collision-Cross-Section)\n22. [Evaluating Ion Mobility Data Acquisition, Calibration, and Processing for Small Molecules: A Cross-Platform Assessment of Drift Tube and Traveling Wave Methodologies](https://pubs.acs.org/doi/abs/10.1021/jasms.5c00056)\n23. [Leveraging pretrained deep protein language model to predict peptide collision cross section](https://www.nature.com/articles/s42004-025-01540-z)\n\n---\n*Topic: Encyclopedia › Physical world and mathematics › Chemistry › Chemical principles and methods › Analytical chemistry › Electrophoresis and ion mobility*\n\n*Initially written Sep 29, 2026 · Edited: Oct 15, 2026; Oct 25, 2026*\n\n*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*\n\nLicense: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license\n",
"same_as": [],
"url": "https://www.edgepedia.org/ion-mobility-separation",
"markdown_url": "https://www.edgepedia.org/ion-mobility-separation.md",
"license": {
"name": "Edgepedia Community License 1.0",
"url": "https://www.edgepedia.org/edgepedia/license",
"summary": "Free with credit, commercial use included. AI training is open to everyone. For other uses, organizations over USD 100M in revenue or 100M monthly users license separately.",
"spdx": "LicenseRef-Edgepedia-Community-1.0"
},
"credit": "\"Ion mobility separation\", Edgepedia (EdgeChat), https://www.edgepedia.org/ion-mobility-separation. Edgepedia Community License 1.0.",
"credit_md": "\"[Ion mobility separation](https://www.edgepedia.org/ion-mobility-separation)\", Edgepedia (EdgeChat), [https://www.edgepedia.org/ion-mobility-separation](https://www.edgepedia.org/ion-mobility-separation). [Edgepedia Community License 1.0](https://www.edgepedia.org/edgepedia/license).",
"credit_html": "\"Ion mobility separation\", Edgepedia (EdgeChat), https://www.edgepedia.org/ion-mobility-separation. Edgepedia Community License 1.0.",
"speakable": "Ion mobility separation, also known as ion mobility spectrometry, is a mass spectrometry technique that separates gas-phase ions by size and shape, and is used in laboratories and portable detectors for explosives."
}