Erratic Or Incorrect Retention Times; Retention Time Troubleshooting - Waters 2410 Operator's Manual

7.2.2 Erratic or Incorrect Retention Times

When you troubleshoot retention time problems, check if retention times:
• Change from run to run or are constant from run to run, but are outside the
allowable range for the assay
• Are due to pressure fluctuations that are short-term (with each pump cycle) or
long-term (over the course of several minutes)
• Are associated with an absolute pressure change, that is, if the pressure is constant
but higher or lower than the normal operating pressure
• Change suddenly at the end of a series of runs, which may indicate that air is
dissolving in the mobile phase, that the mobile phase is degrading, or that the
column is contaminated.
• Change early in a series of runs and tend to become constant or within range after 3
to 4 minutes, which may indicate that the column was not equilibrated, or that the
solvent is not properly degassed and sparged.
To troubleshoot problems with retention times, refer to
Table 7-2 Retention Time Troubleshooting
Symptom
Erratic retention times Air bubble in pump head
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Table
Possible Cause
Degas all solvents, prime
pump (see
Solvent Degassing
Malfunctioning pump check Clean/replace/rebuild pump
valves check valves.
Leaking pump seals Replace pump seals.
Separation chemistry Check mobile phase and
column.
Clogged solvent filters Replace filters.
Chromatography Troubleshooting
7-2.
Corrective Action
Section 4.3.2,
Methods).
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