Thermo Scientific Dionex UltiMate 3000 Series Operating Instructions Manual page 175

Problem
Either no peaks or only few,
poorly resolved peaks appear
in the chromatogram.
Reproducible ghost peaks in
the chromatogram.
Additional peaks appear in
the injection peak.
Triangular peaks
Spikes
Negative peaks
Operating Instructions
Probable Cause
With direct injection or
preconcentration: The solvent
contains too much organic, the
solvent does not contain enough
organic in the solvent, or the
mobile phase is wrong.
With preconcentration: The trap
column is too short, the flow rate
of the loading pump is too high,
and/or the loading time is too
long. The three items interact: If
the trap column is too short,
peaks may be lost because they
are not retained. If the loading
time is too long or if the loading
flow is too high, hydrophilic
peaks may be lost. This also
affects the reproducibility
because the proteins are
transported a long way into the
trap column.
The degassing channels are
contaminated.
The eluents are degraded, dirty or
of poor purity/quality.
Contamination occurs
somewhere in the system.
With gradients, the equilibration
time after the flush cycle is too
short.
There is excessive dead volume.
The column is overloaded (the
concentration of the sample is too
high).
There is electrical interference
from other modules.
For additional causes, refer to the
operating instructions for the
detector.
Sample solvent and mobile phase
differ in composition.
UltiMate 3000 Series:
NCS-3500RS and NCP-3200RS
Remedial Action
Optimize the
chromatographic parameters.
Consider the following: Use a
longer trap column, reduce
the flow rate from the loading
pump, and/or reduce the
loading time.
Rinse the degassing channels
(→ Solvent Rack manual).
Use fresh solvent. Use fresh
and appropriate solvents (MS-
grade).
Flush the system with an
appropriate solvent.
Extend the equilibration time.
Eliminate any dead volume.
Dilute the sample.
Isolate the electrical circuit
from strong current
consumers. Consider
installing an uninterruptible
power supply (UPS).
→ Detector manual
Dissolve the sample in the
mobile phase.
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