Abstract
Copyright 2015 American Association for Aerosol Research
The 891 patent describing a “pressure flow reducer” was regrettably missed in our search of the peer-reviewed literature using keywords “aerodynamic lens” and “focusing inlet.” Notably, this patent has also been missed by other recent reports of high-pressure aerodynamic lenses that transmit particles in this larger size range as well (Williams et. al. 2013, Characterization of an Aerodynamic Lens for Transmitting Particles >1 Micrometer in Diameter into the Aerodyne Aerosol Mass Spectrometer, Atmos. Meas. Tech. Discuss., 6:5033–5063; Lee et al. 2013, Numerical Simulations on Aerodynamic Focusing of Particles in a Wide Size Range of 30 nm–10 μm, Aerosol Science and Technology, 47:1001–1008). The author is encouraged to publish his results in a peer-reviewed journal so it is not missed in literature searches in the future.
In spite of the author's claim, the two systems do not have similar performance in the larger size range needed for our studies on individual cells. The 891 patent performs most effectively in the 1–2 μm range, a size regime where the majority of other inlets for larger particle studies have also been shown to function effectively. However, the Fergenson inlet design has reduced transmission efficiency in the larger size range needed in our studies (∼6 μm). Furthermore, it is important to note that since the newer lens design published by Cahill et al. (2014; Development of a High-Pressure Aerodynamic Lens for Focusing Large Particles (4–10 μm) into the Aerosol Time-of-Flight Mass Spectrometer, Aerosol Science and Technology, 48(9):948–956) does not transmit smaller more abundant (∼1 μm) particles, it avoids interferences which would lead to an overall decrease in the analysis efficiency of the system. These differences in transmission efficiency as a function of size directly determine the useful applications for the lenses. In our case, they enable more efficient transmission and detection of whole cells into our mass spectrometer for single-cell characterization studies.