Characterization of a Herrmann-type high-resolution differential mobility analyzer

ABSTRACT

Aerosol instrument characterization and verification for nanometer-sized particles requires well-established generation and classification instruments. A precise size selection of sub-3-nm charged aerosol particles requires a differential mobility analyzer (DMA), specially designed for the sub-3-nm size range. In this study, a Herrmann-type high-resolution DMA developed at Yale University was characterized in various operation conditions. A relation between sheath flow rate and tetraheptylammonium ion (C₂₈H₆₀N⁺, THA⁺, 1.47 nm, mobility equivalent diameter) was established. The maximum particle size that the DMA was able to classify was 2.9 nm with the highest sheath flow rate of 1427 liters per minute (Lpm), and 6.5 nm with the lowest stable sheath flow rate of 215 Lpm, restricted by the maximum and minimum flow rates provided by our blower. Resolution and transmission of DMA are reported for tetrapropylammonium (C₁₂H₂₈N⁺, TPA⁺, 1.16 nm), THA⁺, and THA₂Br⁺ (1.78 nm) ions measured with two different central electrodes and five different sheath flow rates. The transmission varied between 0.01 and 0.22, and the resolution varied between 10.8 and 51.9, depending on the operation conditions.

Copyright © 2016 American Association for Aerosol Research

EDITOR:

• Jian Wang

Acknowledgments

We wish to thank Professor Fernández de la Mora for fruitful discussions.

Funding

This work was partly funded by European Research Council (ATMNUCLE, 227463), Academy of Finland (Center of Excellence Program projects 1118615 and 139656), Nordic Center for Excellence (CRAICC), European Commission's Seventh Framework program (ACTRIS, contract No. 262254; ACTRIS2, contract No. 654109; PEGASOS, contract No. 265148), Office of Science (BER), and US Department of Energy (The Biogenic Aerosols – Effects of Clouds and Climate, BAECC).