There is a discrepancy in the reported concentration between nta and evquant

There is a discrepancy between measurements based on nanoparticle tracking analysis and the EVQuant protocol[@hartjes2020EVQuant; high-throughput quantification and characterization of extracellular vesicle (sub)populations]. (See: quantifying the concentration of EVs in urine or plasma through confocal microscopy)

The NanoSight is not a reliable instrument for small particles, given that they diffuse very quickly (see: Sources of error in measuring diffusion coefficient through nanoparticle tracking analysis). On the other hand, if the samples are immobilized and imaged through a confocal microscope, it is possible to adjust the settings to become sensitive even to single-molecules.