Biseps, Inc.  Advanced Columns and Methods for Preparative Bio-Chromatography

1. Keep residence time constant - to assure consistent Dynamic Binding Capacity (DBC, mg/ml resin).  
Notes:
    - Residence (or "contact") time is proportional to the column volume (liters) divided by the flow rate (liters per minute). 
    - Dynamic Binding Capacity values are established at different residence times using the "break-through" curves.  Extrapolation to eternal residence time gives maximum possible capacity of the sorbent (also known as a Static Capacity, SC).
    - DBC is considered satisfactory at 50-75% of SC utilization.
    - Dilution of the feed does not alter the required residence time.
    - Dynamic binding capacity depends on the flow rate and on the column volume but NOT on the column "ID-to-Length" ratio.  This ratio is important for the back-pressure (see below) as well as for processes that rely upon the plate number.
    - Residence time depends on the sorbent bead diameter in the power of two.  Thus, the larger the beads the longer saturation time, the slower must be the flow.

2. Keep bed height constant - to assure constant back-pressure. 
Notes:
   - Back-pressure is proportional to the column height in the power of two (assuming the column volume (L) and  the flow (L/min) are kept constant). In other words, the back-pressure is proportional to the column ID in the power of four.
   - Back-pressure is proportional to the sorbent bead diameter in the power of two (assuming that the other column parameters and  the flow are kept constant). Since smaller beads allow for a faster process, the total pressure hike can be quite dramatic.

 3.  Interrelation of the flow rate, DBC, back-pressure, etc. are illustrated on the "DBC Rules" page.