1100 Series Nano Pump Service Manual 99
Troubleshooting and Test Functions 2
Failure to produce peaks, or abnormally small peaks, after injection
There are no peaks, or the peak size is significantly below the typical peak size
for this method with this column.
Table 11 Failure to produce peaks, or abnormally small peaks, after injection: Possible Causes and Suggested
Actions
Possible Causes Suggested Actions Notes
A leak in a sample carrying
area of the system.
• Using a flashlight and absorbent tissue,
carefully check for leaks in the following areas:
a. All micro-sampler valve ports.
b. The junction of the needle and sample loop
capillary.
c. The needle/seat interface.
d. Column inlet and outlet.
e. Flow cell inlet capillary, at the capillary/cell
body junction.
At very low flow rates, a leak may
never accumulate enough liquid to
trigger the module leak sensors. Low
flow rate leaks are also very hard to
see.
The 40 µl chamber of the
micro-sampler metering head
has developed bubbles.
• In the user interface diagnostics, access the
Change Piston function of the micro-sampler
maintenance positions. This function draws the
metering piston fully inward, clearing the
chamber.
• Under flow conditions, activate this function for
at least 5 minutes. The sampler valve must be in
the mainpass position at this time. Any bubbles
which have formed in the chamber will now be
cleared by the flow.
In most applications, only a small
part of the available 40µl metering
head volume is used. At very low
flows, bubbles may form in the
unused space between the metering
piston and the chamber wall. The
bubbles act to defeat the draw of
sample into the needle.
For best results in clearing bubbles,
the mobile phase being pumped
should not contain water.
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