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5
How to Optimize the Performance of Your Module
Delay Volume and Extra-Column Volume
Delay Volume and Extra-Column Volume
The delay volume is defined as the system volume between the point of mixing
in the pump and the top of the column.
The extra-column volume is defined as the volume between the injection point
and the detection point, excluding the volume in the column.
Delay Volume
In gradient separations, this volume causes a delay between the mixture
changing in the pump and that change reaching the column. The delay
depends on the flow rate and the delay volume of the system. In effect, this
means that in every HPLC system there is an additional isocratic segment in
the gradient profile at the start of every run. Usually the gradient profile is
reported in terms of the mixture settings at the pump and the delay volume is
not quoted even though this will have an effect on the chromatography. This
effect becomes more significant at low flow rates and small column volumes
and can have a large impact on the transferability of gradient methods. It is
important, therefore, for fast gradient separations to have small delay
volumes, especially with narrow bore columns (e.g., 2.1 mm i.d.) as often used
with mass spectrometric detection.
The delay volume in a system includes the volume in the pump from the point
of mixing, connections between pump and autosampler, volume of the flow
path through the autosampler and connections between autosampler and
column.
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Agilent 1290 Infinity Binary Pump User Manual
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