How To Configure The Optimum Delay Volume - Agilent Technologies InfinityLab LC Series User Manual

5 How to Optimize the Performance of Your Module

How to Configure the Optimum Delay Volume

How to Configure the Optimum Delay Volume

The design of the Flexible Pump offers a strongly decreased delay volume
compared to standard 600 bar pressure pumps. For the Flexible Pump, mixing is
done in the multi-channel gradient valve at ambient pressure. As all pump parts
in the flow path after mixing contribute to the delay volume, this includes also
pump heads, flow connections, filters, mixers etc. Therefore the delay volume of
a quaternary pump (Flexible Pump) is by design larger than that of a binary
pump.
All listed components including the inlet weaver and pump heads ensure a good
mixing performance resulting in excellent composition precision and accuracy,
highly reproducible retention times and low baseline noise. This ensures best
results for most applications.
Per default, the Flexible Pump does not require and include a Jet Weaver, as
solvents are mixed in the MCGV and mixing is further improved in the inlet
weaver, pump heads and subsequent parts in the flow path. Therefore, no Jet
Weaver is required for most applications.
Jet Weaver high performance mixers are optionally available for demanding
applications, which use solvents in different channels (for example A versus B),
that differ strongly in their UV/Vis absorption, for example by using trifluoroacetic
acid (TFA) as a modifier, which has a high absorbance. Solvent packages created
by the pump may persist until the solvent reaches the detector flow cell.
Absorption fluctuations can then show up as baseline noise, also referred to as
mixing noise. Applications like impurity quantitation or lowest level compound
detection require minimizing this noise. Jet Weavers strongly improve mixing
and therefore reduce baseline noise and improves sensitivity in detection.
Patented Agilent microfluidic technology offers high mixing performance at a low
internal volume. For example, the physical volume of all channels for a 380 µL
mixer only contributes with 150 µL to the pump delay volume (< 350 µL without
Jet Weaver), which is the partial mixer volume that creates a composition change
corresponding to the delay volume.
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