Retention Time Variation; Baseline - Thermo Scientific thermoscientific Vanquish UHPLC System Operating Manual

8.2.6

Retention Time Variation

Decreasing retention times
Possible Cause
Improper mobile phase
composition
Increasing flow rate
Increasing retention times
Possible Cause
Improper mobile phase
composition
Decreasing flow rate
Piston seal leakage
Scattering retention times
Possible Cause
Imprecise solvent
proportioning
Pressure fluctuations
from pump
8.2.7

Baseline

High baseline drift
Possible Cause
System not sufficiently
equilibrated
Unstable
environmental
conditions
Flow cell contaminated
UHPLC System
Operating Manual
Remedial Action
Check premixed mobile phase. Perform an OQ gradient accuracy test. A solvent
selector/proportioning valve may be defective. Contact Technical Support.
Check flow rate settings. Perform OQ flow precision test.
Remedial Action
Check premixed mobile phase. Perform an OQ proportioning test. A solvent
selector/proportioning valve may be defective. Contact Technical Support.
Check capillary connections for leaks. Check flow rate settings.
Check the pump for piston seal leakage (refer to Pump Operating Manual).
Remedial Action
• Perform an OQ eluent proportioning test.
• Clean the inlet check valve or outlet check valve, and replace the check valve if
necessary (refer to Pump Operating Manual).
• A solvent selector/proportioning valve may be defective. Contact Technical
Support.
• Purge the pump.
• Check the compression values and take remedial action (refer to Pump Operating
Manual).
• Check the pump for piston seal leakage (refer to Pump Operating Manual).
• Check the solvent line filters for permeability. Replace the filter frits if necessary
(refer to Pump Operating Manual).
Remedial Action
Flush the system until equilibration. Usually, a volume of 5–10 times the column
volume will be sufficient.
1. Make sure that the temperature and the humidity are constant. You can
determine temperature fluctuations by recording the temperature channels.
2. Verify on the detector that the lamp house cover is properly installed and that the
front doors are closed. Avoid draft.
Clean the flow cell. Replace the flow cell if necessary (refer to Detector Operating
Manual).
8 • Troubleshooting
Page 121