Causes of pressure fluctuations

Because the HPLC system cannot provide stable and accurate flow. When pressure fluctuations occur, most notably, retention times shift. However, the retention time is affected by many factors, and it is impossible for us to control these factors 100%.

During routine testing, the pressure of the HPLC system will fluctuate normally. Generally speaking, the float should be 1%~2% of the working pressure. Different HPLC systems have different purposes and different degrees of floating. Therefore, it is necessary to record the normal use pressure of the system in the daily test. Also be aware of normal pressure cycling in gradient elution.

Symptoms, Sources, and Solutions for Excessive Stress Fluctuations


Location/Symptoms: Air bubbles in the pump

Possible sources: incomplete degassing or flushing, failure of degasser

Solution: Degas the mobile phase, clean the pump, and replace the degasser


Location/Symptoms: Inlet check valve

Possible source: become viscous when using ACN mobile phase

Solution: Sonicate in methanol and replace


Location/Symptoms: High Pressure Connector

Possible source: loose interface or contamination

Solution: Tighten, clean or replace


Location/Symptoms: Low Voltage Connector

Possible source: loose interface or contamination

Solution: Tighten, clean or replace


Location/Symptoms: Multiple pipes for low pressure mixing

Possible sources: Gas leaking from unused solvent line piping, proportional distribution valve leak

Solution: Flush unused pipes with organic solvent and replace the failed proportional distribution method


Location/Symptom: Lack of solvent in pump (failed siphon test)

Possible sources: Proportional distribution valve with clogged/failed inlet pipe filter head

Solution: replace


Location/symptom: seal of pump

Possible sources: worn pump seals

Solution: replace


Location/Symptoms: Piston of the pump

Possible source: broken or scratched piston

Solution: replace


location/symptom: detector

Possible sources: blocked flow cell and blocked outlet piping

Solution: Flush the flow cell and replace the tubing

The most common sources of failure are air bubbles in the pump, sticky check valves, damaged pump seals, damaged pump pistons, and insufficient mobile phase supply.

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