Agilent Technologies agilent 7683B, Installation, Operation And Maintenance Manual

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170 Installation, Operation, and Maintenance
Part 3, Maintenance and Troubleshooting
10
Troubleshooting
Symptom: Contamination or Ghost Peaks
Table 27 Contamination or ghost peak problems
Possible cause Action
Vial cap septum is dissolving in
solvent.
Ghost peaks sometimes appear
when small pieces of septum
material dissolve in the sample.
Make several blank runs to
determine the presence or
absence of the ghost peaks. Check for the following:
•
Be sure the vial septum is flat. If the vial septum is not
flat, the needle tends to core the septum and drop
pieces into the sample. See
“Capping sample vials” on
page 113.
•
Check the needle. If the syringe needle has burrs, it
could cut pieces of the septum and push them into the
sample.
•
Check the vial septum. If the vial septum is not resistant
enough to the solvent you are using, try a more
resistant type.
Sample vials are contaminated. Ghost peaks are sometimes caused by contaminated sample
vials. Try new or clean vials to see if ghost peaks disappear.
Store new vials in a contaminant-free location.
Injection port septum is giving off
volatiles. Make several blank runs with a small piece of aluminum foil
backing the inlet septum. If the contamination peaks
disappear, they were probably due to the septum. Try
replacing the septum you usually use with another type.
Column is contaminated.
High molecular weight samples
that contain residues may cause
the syringe, the inlet liner, or the
first few inches of column to
become contaminated. Do the following:
•
Replace or clean and deactivate the inlet liner.
•
Examine the first few inches of a capillary column for
foreign material by holding a light behind it. If possible,
remove the contaminated section.
Sample is not stable. Some samples change with heat or ultraviolet light. Check the
sample stability.
There are several ways to reduce the change:
•
Use the tray quadrant to cool the sample.
•
Use amber sample vials.
•
Store the samples in a protected environment.