I'm trying to understand what are theoretical speed limits in RPLC from the perspective of diffusion.
This is a purely theoretical thought experiment.
If you have a molecule carried by a solvent flow and you ignore all the aspects which prevent you from getting good separation at speed in real life (resistance to mass transfer due to geometry of the stationary phase, resistance to flow, viscous heating, etc) and focus solely on micro-scale interaction of an analyte popping out of the mobile phase and into the stationary phase, could we say that this is in fact the ultimate boundary in terms of LC speed?
I.e. how fast the flow would have to be [linear velocity] to say that we can't have any useful chromatography at it because analytes are not given enough contact time?
I'm guessing the diffusion driven interactions (particle translation from flow to solid) are around 10^4-10^5 mm/s (guesstimate) while we flow solvents typically at 10^0 to 10^1 mm/s.
Any thoughts on that?

Do you know what is currently the speed record in LC? (in mm/s of solvent flow)
(I was trying to find that but couldn't)

I'm now routinely flowing 20-30 mm/s though various columns and getting very good separations.
Would 200 mm/s work as well? (theoretically, ignoring all the stationary phase geometry aspects and pressure)