Exceeding a resolving power of 50 for virus size determination by differential mobility analysis

A recently described DMA designed for high resolution viral particle analysis (Perez-DMA; Perez -Lorenzo et al, 2020) is modified to decrease the relative peak full width at half maximum (FWHM) below previously achieved approximate to 3.3%. The electrode radii at the outlet slit (R1 = 1.01 cm; R2 = 2 cm) and the working length are almost unchanged (L = 114.9 vs. 116 mm). The laminarization trumpet and the radius of the curve merging the trumpet to the working section are both considerably widened to improve gas flow laminarization. DMA evaluation with salt clusters is improved by reducing the flow resistance at the gas outlet, to reach substantially larger sheath gas flow rates Q near 1700 L/min. Tests with tetraheptylammonium bromide clusters with a center rod diverging at 3? demonstrate FWHM<2.7%, without indications of performance loss due to turbulence even at 1700 L/min. Correcting these high flow rate data for diffusive broadening reveals a maximal DMA FWHM in the limit of non-diffusing particles and zero sample flow, FWHM infinity = 1.8%. An uncorrected peak width approaching 2% is independently demonstrated at much lower flow rates of sheath gas with two recently described bee virus particle standards having singularly narrow size distributions at mean diameters of 38 and 17 nm. Correcting raw 38 nm particle peak widths for broadening due to diffusion and aerosol to sheath gas flow rate ratio q/Q shows an even more ideal response with FWHM infinity<1%, where this value includes nonidealities in the DMA as well as possible lack of monodispersity in the viral particles.

Automated summary

A DMA designed for high resolution viral particle analysis has been modified to improve gas flow laminarization, leading to more accurate analysis of viral particles. Experimental tests have been conducted at different flow rates to validate the performance of the DMA under varying conditions.