Failure To Produce Peaks, Or Abnormally Small Peaks, After Injection - Agilent Technologies 1100 Series System Manual

Capillaries which are
internally broken, especially
those capillaries located in a
chromatographically
significant area.

Failure to produce peaks, or abnormally small peaks, after injection

Symptoms:
There are no peaks, or the peak size is significantly below the typical peak size for this
method with this column.
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.
The 40 µl chamber of the •
micro-sampler metering head
has developed bubbles.
1100 Series Capillary LC System Manual
• Refer to chapter 3 for advice on diagnosing
an internally broken capillary. Check
capillaries for an internal break, particularly
the needle-seat capillary, the sampler valve-
to-column capillary and the flow cell inlet
capillary.
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.
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.
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Basic System Troubleshooting
Capillaries which have been
crushed by module covers are
often broken internally, and may
show no external evidence of a
break.
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.
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.
4