What does column volume, buffer volume and purified collection volume mean?

To clarify what these terms mean in the context of running a qEV column:

'Column volume' - is the volume of the resin beads within the column bed.

'Buffer volume' - refers to the volume of buffer that elutes from the column before the particles/molecules of interest are observed. This is immediately followed by the purified collection volume. 

'Purified Collection Volume (PCV)' - is the volume of sample purified by the size exclusion column containing the particles of interest (EVs/lipoproteins/proteins). This is typically collected as separate fractions, but should be referred to as 'X.X mL beyond the buffer volume of XX.X mL' rather than as fraction 1, 2, 3 etc as this allows for better communication of where the particles of interest eluted. For example, 'On a qEVsingle/35, using a buffer volume of 1.0 mL, the particles of interest were found between 1 and 2 mL of the PCV' communicates to other researchers how to isolate those same particles from the same sample type.

This is important for standardisation and precise isolation as the buffer volumes differ depending on column size/dimensions and resin type used, particularly with respect to pore size.