High-pressure mixing systems, dwell volumes

Reduced dwell volume High-pressure mixing system, low-volume mixer... 

Also known as gradient delay volume, system dwell volume is the liquid holdup volume of the HPLC system from the point of solvent mixing to the head of the column. This includes the additive volumes of the injector, the sample loop, all fluidic connection tubing, and any internal pump volumes of a low-pressure mixing system. The typical dwell volume of a modem HPLC is 0.5-2 mL, but can be as high as 5-7 mL in older systems. 

The dwell volume is the volume within the HPLC system from the point where the solvents are mixed to the entrance of the column. In a low-pressure system it consists of the volumes of the proportioning valve, the mixer, the pump head, the injector and the connecting capillaries. In a high-pressure system it is smaller because only the mixer, injector and the capillaries add their volumes. 

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