The HPLC pump is the “heart” of the chromatography system; its operational stability directly determines the accuracy of analytical results. During experiments, HPLC pumps often suffer from pressure anomalies, leaks, no flow, etc., which not only delay progress but also compromise data reliability. This article systematically addresses common HPLC pump failures, detailing symptoms, root cause analysis, and practical solutions, along with scientific daily maintenance recommendations to help laboratory personnel quickly locate problems, efficiently resolve faults, and ensure smooth HPLC experiments.
I. HPLC Pump Pressure is Zero or Very Low, No Liquid Flows Out
Common Causes
Large amount of gas trapped in the pump (an easily overlooked cause)
Purge valve not fully closed or valve body damaged
Pump seals severely worn, causing internal leakage
Solvent inlet filter clogged (often happens if not cleaned regularly)
Mobile phase depleted or filter not submerged below the liquid surface
Troubleshooting Steps (in order of priority)
Check basic conditions first: Verify that there is sufficient mobile phase in the solvent bottle and ensure the inlet filter is fully submerged. If mobile phase is low, refill and prime the system.
System priming: Open the purge valve, set the flow rate to 5 mL/min, and purge until no continuous bubbles emerge from the pump outlet. If many bubbles persist, use a 50 mL syringe at the pump outlet to assist in drawing out air.
Check purge valve status: If pressure cannot be built even after purging, confirm the purge valve is completely closed; replace the valve body if damaged.
Check for leaks and blockages: Observe the pump head for leaks – if present, replace the seals. Remove the solvent inlet filter and sonicate it (or replace with a new one) to avoid poor suction.
II. HPLC Pump Pressure Fluctuates Violently, Baseline Noise is High
Core Causes
Small bubbles remaining in the system (often due to insufficient degassing)
Check valve contamination or malfunction
Partially blocked inlet filter (not cleaned regularly)
Slight wear of pump seals, causing internal leakage
Inhomogeneous mixing or inadequate degassing of mobile phase
Solutions
Degas mobile phase: Ensure all mobile phases are degassed by sonication (≥15 min) or use an online degasser to continuously remove bubbles.
Thoroughly purge and check sealing: Perform system purging and inspect all tubing connections for tightness to prevent air ingress.
Clean check valves: Remove the check valves, place them in isopropanol or acetone, and sonicate for 20 minutes (note the installation direction to avoid reversal).
Treat inlet filter: Remove the inlet filter; if clogged with salt crystals, sonicate it in 10% dilute nitric acid for 15 minutes, then rinse thoroughly with pure water.
Inspect seals: If pressure still fluctuates after the above steps, check the pump seals for wear and replace if necessary.
III. HPLC Pump Pressure is Abnormally High
Main Causes
Blocked column, guard column, or in‑line filter (accumulated sample impurities)
Blocked tubing connections (e.g., needle, capillary)
Flow rate set too high (exceeding pump or column pressure limits)
Failure to flush after using buffered mobile phases, causing salt precipitation and blockage
Step‑by‑Step Troubleshooting
Isolate segments: First disconnect the column and connect the pump outlet directly to the detector using a union. If pressure returns to normal, the fault lies in the column/guard column – flush the column (reverse with a suitable solvent) or replace it.
Check upstream components: If pressure remains high, sequentially check the in‑line filter, autosampler needle seat, and connecting capillaries. Loosen each joint one at a time while monitoring pressure changes. Once the blockage is located, flush with a suitable solvent or replace the blocked part.
Daily prevention: After using buffers, flush the system with pure water for at least 30 minutes to thoroughly remove salt residues and avoid precipitation blockages.
IV. HPLC Pump Pressure is Abnormally Low / Slowly Drops
Common Fault Points
Leak in the system (fittings and pump head are frequent leak points)
Worn pump seals, causing internal leakage
Check valves not sealing tightly (due to dirt or aging)
Damaged ferrule on a fitting (improper installation or long use)
Troubleshooting Procedure
Check for leaks: Wipe all tubing connections with a paper towel (pay special attention to pump head, mixer, and injector). If the towel is wet, tighten the fitting (moderate force to avoid overtightening).
Inspect pump head and seals: If the pump head shows signs of leakage, replace the seals. If pressure remains low, check whether the check valves are sealing properly – clean or replace them.
Handle tubing and ferrules: Replace damaged ferrules. When reinstalling tubing, ensure the cut end is smooth (use a dedicated cutting tool) to prevent poor sealing.
V. Leakage from HPLC Pump Head or Fittings
Key Causes
Aged or worn pump seals (primary cause, common after long use)
Improper tightening of fittings (too tight or too loose)
Damaged ferrule or uneven tubing cut
Aged pump head components (e.g., failed check valve seal)
Emergency Handling and Prevention
Immediately stop the pump: As soon as a leak is detected, stop the pump to avoid wasting mobile phase or damaging other components.
Address pump head leaks: If seals are worn, replace them (consider proactive replacement every 3–6 months to reduce unexpected failures).
Maintain fittings and tubing: Inspect fittings; replace damaged ferrules. When installing tubing, use a dedicated cutter for a smooth end; follow the “finger‑tight plus 1/4 turn” rule to avoid over‑ or under‑tightening.
Regular inspection: Check the pump head and fitting seals weekly to detect and correct small leaks early.
Daily Maintenance and Preventive Measures for HPLC Pumps
Proper daily maintenance can greatly reduce the probability of HPLC pump failures and extend instrument service life. Specific recommendations are as follows:
Mobile phase preparation: All mobile phases must be filtered through a 0.45 μm (or 0.22 μm, depending on column requirements) membrane to remove particulates. Degas by sonication (or use an online degasser) before use to avoid introducing bubbles.
Daily cleaning: After experiments, flush the system with pure water for at least 30 minutes (to remove buffer salts), then with methanol or acetonitrile for 15 minutes, and finally store the pump in pure organic solvent (to prevent corrosion or contamination).
Regular consumable replacement: Establish a replacement schedule – pump seals every 3–6 months, inlet filter checked monthly (replace if clogged), check valves cleaned or replaced every 6–12 months.
Periodic calibration: Calibrate the pump flow accuracy every six months to ensure operating parameters meet experimental requirements.
By following these HPLC pump troubleshooting methods and a disciplined daily maintenance routine, you can effectively improve chromatography system stability, ensure accurate experimental data, and reduce delays caused by pump failures. For complex faults (e.g., pump motor failure, circuit board issues), promptly contact the instrument manufacturer’s professional service engineers to avoid secondary damage from disassembly.
