A High Resolution Differential Mobility Analyzer with Extended Size Range for Viral Particle Studies
LUIS-JAVIER PEREZ-LORENZO, Jerzy Kozlowski, Juan Fernandez de la Mora,
Yale University Abstract Number: 538
Working Group: Instrumentation and Methods
AbstractPerez-Lorenzo et al. (J. Aerosol Sci. 151, 105658, 2021) have recently described a Differential Mobility Analyzer (DMA) producing very narrow mobility peaks (HWFM below 2%) with certain viral particles having diameters of up to 60 nm. Their DMA had an outer cylinder radius of 2 cm and an inner electrode converging conically with 3
o up to an inner radius of 1 cm at the exit slit. Their limited size range may be theoretically extended to larger particles by decreasing the gap between both electrodes. However, earlier attempts with this strategy led to inferior resolution due to several possible causes. First, high concentricity is harder to achieve with a reduced inter-electrode gap. Second, at fixed sheath gas flow rate Q, a reduced gap increases flow speed and Reynolds number, favoring an earlier turbulent transition. The successful model here tested was built with especial concentricity requirements. It also used a conical inner electrode converging at 0.5
o up to an inner radius of 1.6 cm at the outlet slit. Finally, a new scheme to mount the laminarization screens was implemented. The DMA has been tested with several viral particles, including the 29 nm bacteriophage PhiX174. The peak width decreases at increasing sheath gas flow rate Q up to a Reynolds number slightly above 1900, where FWHM approaches 50. The instrument has been used to investigate several relatively large viral particles, including the bacteriophages T2 and T4. Hogan et al. have reported that T4 is fragmented during the electrospraying process leaving only an ~80 nm capsid. We confirm their finding in sprays from 10 mM aqueous ammonium acetate. However, a larger and apparently intact ~100 particle is observed when spraying from deionized water. The DMA achieves an electric field of 30 kV/cm at which the mobility of T2 and T4 is field dependent.