1 research outputs found
Super-resolution imaging reveals resistance to mass transfer in functionalized stationary phases
Chemical separations are costly in terms of energy, time, and money.
Separation methods are optimized with inefficient trial-and-error approaches
that lack insight into the molecular dynamics that lead to the success or
failure of a separation and, hence, ways to improve the process. We perform
super-resolution imaging of fluorescent analytes in four different commercial
liquid chromatography materials. Surprisingly, we observe that chemical
functionalization can block over fifty percent of the porous interior of the
material, rendering it inaccessible to small molecule analytes. Only in situ
imaging unveils the inaccessibility when compared to the industry-accepted ex
situ characterization methods. Selectively removing some of the
functionalization with solvent restores pore access without significantly
altering the single-molecule kinetics that underlie the separation and agree
with bulk chromatography measurements. Our molecular results determine that
commercial stationary phases, marketed as fully porous, are over-functionalized
and provide a new avenue to characterize and direct separation material design
from the bottom-up