Decision Tree: Retention Time Shift
Symptom: peaks move earlier/later; peak ID becomes wrong; method fails.
Do not re-identify peaks until carrier/temperature stability is confirmed.
Step-by-step isolation
1) Check carrier pressure/flow stability (most common cause): verify supply, regulator hunting, flow controller status.
2) Verify oven temperature: confirm correct setpoint, no deviation alarms, stable trend.
3) Check column/valve configuration: ensure correct stream selected, correct method loaded, valve timing unchanged.
4) Check for leaks/restrictions: leaks usually shift RT; restrictions/plugging can also shift RT and distort peaks.
5) Confirm carrier type/purity: wrong carrier or contamination changes retention behavior and baseline.
6) If RT still shifted after stability checks:
- Suspect column aging/contamination or oven sensor drift.
- Verify with calibration standard chromatogram and compare.
7) Corrective actions:
- Stabilize regulators/flows, fix leaks, replace filters.
- Service oven control loop if temp drift exists.
- Clean/replace column only after confirming utilities are correct.