1290 Infinity II High-Speed Pumps User Manual 87
5 Optimizing Performance
How to Configure the Optimum Delay Volume
How to Configure the Optimum Delay Volume
The physical delay volume of the pump depends primarily on the use of the Jet
Weaver mixer. For UV detection, the Jet Weaver should always be used but for
mass spectrometric detection the user can decide to bypass the Jet Weaver to
reduce the delay volume. This only makes sense for ultrafast gradient operation
(less than 0.5 min) or for use with very small volume columns. If the Jet Weaver
is bypassed, the connection tubing to the autosampler is routed directly from the
purge valve.
Sometimes it may be advisable to increase the delay volume in the pump.
Specifically this can be the case when UV detection is employed and a strongly
UV-absorbing compound has been added to the mobile phase. This can have the
effect of emphasizing any pump noise and the most common example is the use
of trifluoroacetic acid (TFA) in the analysis of proteins and peptides. The effect
can be mitigated by increasing the mixer volume.
The following different Jet Weaver configurations are available:
• The Jet Weaver (Jet Weaver 35 μL/ 100 μL (G7120-68135) or Jet Weaver
35 µL/ 100 µL Bio-Compatible (G7132-60135)) has two alternative volumes in
the same unit.
The switch from the lower volume, 35 µL, to the higher volume, 100 µL, is
done by uninstalling it, turning it around from front to back and re-installing it,
see “Change Configuration or Replace the Jet Weaver” on page 150. The delay
volume increases by approximately 31 µL and the baseline performance with
additives like TFA improves. The configuration of the Jet Weaver is logged
automatically by an attached RFID tag.
• The 380 µL Jet Weaver high-performance mixer (Jet Weaver 380 μL
(G7120-68380) or Jet Weaver 380 µL Bio-Compatible (G7132-68380)) is
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, it can be installed when 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. The 380 µL
Jet Weaver strongly improves mixing and therefore reduces baseline noise
and improves sensitivity in detection. Patented Agilent microfluidic
technology offers high mixing performance at a low internal volume of
380 µL.
Before disconnecting a Jet Weaver from the flow path, flush it with organic
solvent (50 % isopropanol in water). Avoid leaving water or buffers inside the Jet
Weaver, which may cause the growth of micro-organisms like algae or bacteria.
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