Delay Volume And Extra-Column Volume; Delay Volume - Agilent Technologies Infinity II 1290 User Manual

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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.
For the 1290 Infinity II Flexible Pump, all pump parts downstream the
MCGV contribute to the delay volume, i.e. inlet weaver, pump heads,
capillary connections, filters and the optional Jet Weaver.
40 Agilent 1290 Infinity II Flexible Pump User Manual