This section applies to binary pumps, quaternary pumps, and dual pumps.
The gradient delay volume of an HPLC system is defined as the volume of the entire flow path between the point where the gradient is formed and the point where the mobile phase enters the column. Thus, the gradient delay volume of an HPLC system is the volume that the pump must deliver until a change in solvent composition reaches the column inlet.
No. | Description |
---|---|
1 | Pump with |
1a | Point where the gradient is formed: Quaternary pump: The gradient is formed after the proportioning valve. Dual pump: The gradient is formed after the proportioning valve (with each of the two pumps). Binary pump: The gradient is formed in the purge/sensor unit. |
2 | Autosampler |
3 | Column |
4 | Detector |
5 | Gradient delay volume of the system |
Reducing the gradient delay volume allows changes in the solvent composition to become effective on the column much earlier and thus, having a faster effect on the elution of analytes.
The pump contributes to the system gradient delay volume by the dwell volume (see Pump-Specific Information). For the dwell volume of the pump, see Performance Specifications.
In the standard configuration, the pump has been optimized for the dwell volume and ripple. You can adapt the dwell volume or ripple to your requirements by replacing the mixing system with which the pump is shipped with a mixing system with a different volume:
Mixing system with lower volume
Operating the pump with a lower volume mixing system reduces the dwell volume of the pump and thus, the gradient delay volume of the system but increases the ripple.
Consider installing a mixing system with lower volume for gradient separations at low flow rates (for example, less than 100 µL) or for very steep gradients.
Mixing system with higher volume
Operating the pump with a higher volume mixing system reduces the ripple but increases the dwell volume of the pump and thus, the gradient delay volume of the system.
For information about the available mixing systems, see Available Mixing Systems.