Thermo Scientific Dionex UltiMate 3000 Series Operating Instructions Manual page 113

Problem
Negative peaks
Wavelength
verification fails.
Poor peak area
precision
Operating Instructions
Fluorescence Detectors FLD-3100 and FLD-3400RS
Probable Cause
Sample solvent and mobile
phase differ in composition.
The fluorescence of the solute
is lower than the fluorescence
of mobile phase.
The fluorescence of the
substance or eluent is
quenched by other
components.
Wrong polarization of the
analog output interface.
The flow cell is incorrectly
installed.
The wavelength calibration is
not within the acceptable
range.
The flow cell is contaminated.
The system does not meet the
required conditions.
The autosampler draws air
from the vial.
There are air bubbles in the
syringe or the autosampler
fluidics.
There is an air bubble in the
flow path.
The draw speed is too high.
The gas content of the sample
is too high or saturated.
The needle is clogged or the
needle tip is deformed.
The autosampler, the injection
valve, or the syringe valve is
not tight.
UltiMate 3000 Series:
Remedial Action
Dissolve the sample in the mobile phase.
Select a different wavelength pair. Use a
mobile phase with less background
fluorescence.
Consider using the negative peaks for
quantification.
Check the analog output polarization.
Verify that the flow cell is seated
correctly and that the screws are
tightened finger-tight.
Perform a wavelength calibration
(→ page 90).
Flush the flow cell (→ page 109).
Observe the conditions on page 90. If
the procedure is repeatedly interrupted,
contact Service.
There is not enough amount of sample
in the vial, the needle height setting is
incorrect (→ Autosampler Manual), or
there are too many replicates.
Flush the syringe (→ Autosampler
Manual).
Non-degassed wash liquid is used.
Degas the wash liquid (→ Autosampler
Manual).
Perform a wash cycle (→ Autosampler
Manual).
Reduce the draw speed (→ Autosampler
Manual).
Reduce the draw speed (→ Autosampler
Manual).
Degas the sample if possible.
Replace the needle (→ Autosampler
Manual).
→ Autosampler Manual
Page 105