Agilent Technologies 1290 Infinity LC System System Manual And Quick Reference page 67

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Optimization of the Agilent 1290 Infinity LC System
How to Achieve Lowest Carry Over
The flush port is located above and behind the needle seat and a peristaltic
pump delivers the wash solvent. It has a volume of 0.68 ml and the peristaltic
pump delivers 6 ml/min, which means the flush port volume is completely
refilled with fresh solvent in 7 s. If the flush port is selected, the user can set
how long the outside of the needle is to be washed with fresh solvent. This may
be as low as two or three seconds in routine situations where carryover is less
of a problem and 10 to 20 s for more complete washing. It is recommended
that washing the outside of the needle in the flush port should be standard
procedure to avoid contaminating the needle seat. If the needle seat becomes
contaminated it will have to be back-flushed, by manually changing the flow
connections, to clean it. This is one of the tasks that can be automated using
the Flexible Cube module.
The flush port and its solvent delivery pump and tubing should be regularly
flushed to ensure the lowest carryover. For example, before using the system
each day, prime the flush pump for three minutes with appropriate solvent.
When other measures have failed to eliminate carryover it might be that
analyte is sticking inside the injector valve. The injector valve can be set to
make additional switching movements to clean out the flow path in the valve if
problems occur here with carryover. If the problem compounds need a high
percentage of organic phase for elution, it is recommended to switch the
injection valve at the high percentage of organic phase after the last peak has
eluted. It is also recommended to switch the injection valve again after the
initial conditions for the mobile phase have stabilized. This ensures that the
bypass groove in the rotor seal of the valve contains the gradient start
conditions, which is especially important for flow rates below 0.5 ml/min.
For samples where the outside of the needle cannot be cleaned sufficiently
with water or alcohol from the flush pump use wash vials with an appropriate
solvent. With an injector program several wash vials can be used for cleaning.
Agilent 1290 Infinity LC System Manual and Quick Reference 67