AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
The Radial Opposed Migration Ion/Aerosol Classifier (ROMIAC)
WILTON MUI, Andrew Downard, Daniel Thomas, Jesse Beauchamp, John Seinfeld, Richard Flagan, Caltech
Abstract Number: 61 Working Group: Instrumentation and Methods
Abstract The radial opposed migration ion/aerosol classifier (ROMIAC), a novel differential mobility analyzer (DMA) that is capable of high resolution of particles as small as 1 nm, is presented. We discuss the instrument design, particle trajectory simulations, and experimental validation of the ROMIAC as an aerosol classifier. The ROMIAC uses a radial geometry and an isopotential inlet and outlet design to minimize diffusive losses. Monte Carlo COMSOL simulations were used to further refine the design for successful transmission of sub–3 nm particles. Classification of tetra–alkyl ammonium halide, peptide, and protein ions, followed by detection of the ions by a linear trap quadrupole mass spectrometer demonstrated the successful use of the ROMIAC for selecting 1.16–2.14 nm particles with a resolution of ~20. The performance of the ROMIAC against the traditional DMA was assessed from dimensionless quantity analysis, revealing an extended domain of capability of the ROMIAC for classifying nanoparticles and gas ions that would otherwise be impossible with the DMA due to diffusional losses or turbulent flow conditions. The ROMIAC is a very compact (~10 cm in diameter and length), inexpensive instrument with low auxiliary pump requirements (<40 lpm) that can achieve high resolutions for classification of particles throughout the nanometer size range.