User manual

78 Agilent 1260 Infinity High Performance Autosampler User Manual
5 Optimizing Performance
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.
The optimum carry- over performance of the Autosampler is achieved after a
run- in period of new instruments or after the exchange of consumable parts
(like needle, needle seat and valve parts). During injections in this period,
surfaces of these parts adjust to each other. After this period, we recommend
back- flushing the needle seat in order to get the sealing areas between needle
and needle seat clean. Regular Preventive Maintenance service is
recommended as the carry- over performance of the Autosampler depends on
the integrity of these consumable parts. Using the G4227A Flexible Cube will
additionally improve the carry- over performance and life time of these parts.