Differential Mobility Analysis for optimum separation of ions and charged particles
The Differential Mobility Analyzer, DMA is a peculiar IMS device combining a flow field U and an electric field E between two parallel plates. It disperses a beam of ions into a fan, such that only the ions with a well defined electrical mobility are transmitted into an outlet slit leading to the MS inlet. The main advantage of the DMA over other more familiar IMS instruments is the simplicity of its integration as a front-end into a preexisting MS with an atmospheric pressure source. The integration to form a DMA-MS instrument requires essentially no change in the vacuum system of the MS. The DMA measures true mobility, generally in air, N2 or CO2). The DMA is also unique in enabling mobility determination of ions as produced by the ES source, without the structural modifications that tend to arise when an ion crosses a vacuum interface, an ion guide, or is injected into a drift cell.
Figure 1: Operation of the differential mobility Analyzer (DMA). Ions are fed through a slit on the upper plate, and dispersed into a fan by combined fluid flow (rightwards) and electric (downwards) fields. Ions of a pre-selected electrical mobility are drawn through an exit hole into the mass spectrometer.
Following up the R&D by SEADM’s Technical Consultant, the Yale Professor Juan Fernandez de la Mora, during the last two decades, SEADM offers two types of DMA’s, depending on the geometry of electrodes: parallel plate (termed DMA P5) and axisymmetric (termed Half Mini). Currently, tens of customers in fields such as combustion, atmospheric science or nanoparticle generation benefit from best-in-class performance.
Our systems are delivered alongside the complete range of accessories for stand- alone operation, including ionization source, sheath recirculation flow loop and measurement system (either SEADM electrometer Lynx E12 or a mass spectrometer). Besides, SEADM offers its Mobility Front End offering outstanding advantages working as mobility filter in series with your favourite mass spec. If you are interested in the most sensitive vapor analysis equipment, offering LoDs as low as 0.01 ppq, take a look to our TD-LFSESI-DMA-MS range. Finally, if you are a system developer and you want to integrate our DMAs into your workbench, the DMA Cells are also available.
Main advantages of SEADM’s DMAs include:
- Operation in supercritical regime: carefully engineered architecture allow laminar flow even in spite of their high Reynolds numbers (>>2000) and high sheath flow rates (up to 1500 lpm)
- Since diffusion broadening is minimized, unbeatable resolving powers of 80 and 30 (peak voltage)/FWMH are achieved for the parallel plate and the axisymmetric DMA, respectively.
- Unlike conventional IMS (drift tube) systems which filtrate ions in the time domain, the DMA does it continuously, i.e., in the space domain; therefore duty cycle is 100%, and ion transmission maximized.
- Differently from competing solutions, SEADM’s DMAs measures true mobility generally in air, N2 or CO2, as a variable fundamentally related with molecule/nanoparticle structure and size.
- Soft ionization provided (electrospray). Likewise, DMAs determine the mobility of ions as produced by the ES source, without the structural modifications that tend to arise when an ion crosses a vacuum interface, an ion guide, or is injected into a drift cell.
- Particularly, the planar plate DMA is a unique device, offering compelling simplicity of integration as a front-end into a preexisting MS with an atmospheric pressure source (the integration to form a DMA-MS instrument requires essentially no change in the vacuum system of the MS).
You can take a quick look to selected customer application examples (Figure 2). For more information please see our DMA technology brochure and discover what DMA can do for you.
If you have questions, please do not hesitate to contact, SEADM’s engineering team will be glad to analyse your use case and see how we can help.
DMA product range
Stand-alone nanoparticle and molecule classifiers (ESI*-DMA-E*):
High resolution, high transmission studies of nano-aerosol processes
High resolution analysis of nano-particles and molecules
Unbeatable performance up to 5 nm
Mobility Filter for MS (LFSESI*-DMA):
Differential Mobility Analyzer Add-on for Mass Spectrometers
Superior sensitivity and selectivity for real-time mass spectrometry at affordable costs
Vapor analysis/detection (TD-LFSESI-DMA-MS):
Ionic mobility system for your MS
For advanced Vapor Analysis with Your MS
Advanced measurement through triple filtration Volatility – Mobility – Molecular Mass
For superior Sensitivity and Selectivity Vapor Analysis in Real Time
DMA cells (for developers):
SEADM’s planar Differential Mobility Analyzer
Separation of molecules or particles through their electrical mobility
Portable, light weight DMA for high-resolution classification of 0-30 nm particles
* ESI: Electrospray ionizer; E: electrometer; LFSESI: Low Flow Secondary Electrospray Ionizer;
- PATENT: M. Amo, D. Zamora, A. Casado, G. Fernandez de la Mora, G. Vidal de Miguel, J. Fernandez de la Mora, “Method for detecting atmospheric vapors at parts per quadrillion (PPQ) concentrations”, USPTO 9,297,785, Mar. 29, 2016. link
- PATENT: P. Martínez Lozano, J. Fernandez de la Mora, “A method to classify persons and organisms based on odor patterns from released vapors of polar substances”, USPTO 12/556,247, Jul. 21, 2015, publication pending
- PATENT: G. Vidal de Miguel, M. Macía, “Method and apparatus to improve the separation capacity in a sequence of ion filters incorporating at least two ion mobility analyzers”, USPTO 8,907,275 B1, Dec. 9, 2014, link
- PATENT: G. Vidal de Miguel, “Ionizer for vapor analysis decoupling the ionization region from the analyzer”, USPTO 8,461,523 B2, Jun. 11, 2013, link
- PATENT: G. Vidal de Miguel, “Method and apparatus to produce steady beams of mobility selected ions via time-dependent electric fields”, USPTO 8,378,297 B2, Feb. 19, 2013, link
- PATENT: J. Fernández de la Mora, “Use ion guides with electrodes of small dimensions to concentrate small charged species in a gas at relatively high pressure”, USPTO 8,362,421 B2, Jan. 29, 2013, link
- PATENT: J. Fernandez de la Mora, A. Casado, G. Fernandez de la Mora, “Method and apparatus to accurately discriminate gas phase ions with several filtering devices in tandem”, USPTO 8,278,622 B2, Oct. 2, 2012, link
- PATENT: G. Vidal de Miguel, J. Fernandez de la Mora, “Method and apparatus to sharply focus aerosol particles at high flow rates and over a wide range of sizes”, USPTO 8,247,764 B2, Aug 21, 2012, link
- PATENT: F. Estevez-Molinero, J. Rus, J. Fernandez de la Mora, J.J. Schmitt, “Improved coupling between axisymmetric differential mobility analyzers and mass spectrometers or other analyzers and detectors”, USPTO 8,232,519 B2, Jul. 31, 2012, link
- PATENT: G. Vidal de Miguel, “Ionizer for vapor analysis decoupling the ionization region from the analyzer”, USPTO 8,217,342 B2, Jul. 10, 2012, link