Preventive Maintenance and Troubleshooting
Chromatographic symptoms
124
Contamination or ghost peaks
Figure 69. Contamination or ghost peaks
Vial cap septum is dissolving in solvent
Ghost peaks sometimes appear in the chromatogram when small pieces of vial
septum material dissolve in the sample. Make several “blank” runs to
determine the presence or absence of the ghost peaks. Check for the following:
• If the vial septum is not flat, the needle tends to core the septum and drop
pieces into the sample. See “Crimp capping sample vials” on page 30.
• If the syringe needle has burrs, it could cut pieces of the septum and push
them into the sample. See “Inspecting syringes” on page 51.
• 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.
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