- HPLC column
- UPLC column
- Void volume
For columns with fully porous packings, use the formula pi * (r)2 * L * 0.66.
For columns with superficially porous packings, use the formula pi * (r)2 * L * 0.49.
The formulas shown above merely reflect an estimate of the void volume of a packed column (interstitial volume plus the pore volume).
To understand what the actual column void volume is for a particular column installed on a particular system, you must make an injection with a compound that does not retain on the packing material. Once a void marker peak is injected, you can use the following formula to determine column void volume:
Retention time of void peak (Vo) * Flow Rate
Example: If an acetone peak retains at 2.32 min, and the flow rate is 0.85 mL/min, then:
Vo = 2.32 min * 0.85 mL/min
Vo = 1.972 mL