High-performance liquid chromatography (HPLC) is a core instrument for precision analysis and testing in pharmaceuticals, food, environmental monitoring, chemicals, biopharmaceuticals, and many other fields. The operational stability of the instrument and the precision and reproducibility of the data it generates directly determine the compliance and validity of experimental testing, product quality control, and research data. As a high-precision instrument composed of critical components including a high-pressure solvent delivery pump, injection system, chromatographic column, detector, and fluid lines, HPLC is subject to long-term, high-frequency use. Improper operation and inadequate maintenance can readily lead to baseline drift, pressure anomalies, peak distortion, poor data reproducibility, and line blockages — issues that not only compromise analytical results but also significantly shorten the service life of both the instrument and columns, while increasing operational and maintenance costs.
To standardize laboratory operating procedures, reduce equipment failure rates, and ensure long-term stable performance, this article presents a comprehensive and actionable HPLC maintenance and care guide based on industry-standard practices and hands-on operational experience. It covers core areas including daily usage specifications, systematic periodic maintenance, care for idle equipment, and prevention of common failures — suitable for laboratory applications across all industries.
I. Core Daily Usage Specifications and Immediate Maintenance
The daily startup, operation, and shutdown procedures are the most fundamental and critical aspects of maintenance — most hidden failure risks originate from lapses in routine operation.
The mobile phase is the "lifeline" of the HPLC system. Poor mobile phase management is the root cause of 80% of system failures.
Water quality and reagent requirements: Ultrapure water (resistivity ≥ 18.2 MΩ·cm) must be used for preparing aqueous phases; ordinary purified water is not acceptable, as impurities and ions can be introduced into the system. All mobile phase reagents must be of HPLC grade; analytical grade reagents are prohibited, as they can introduce impurities that block lines and columns.
Filtration and degassing: All mobile phases must be filtered through 0.22 μm or 0.45 μm microporous membranes before use to remove fine particles. After filtration, ultrasonic degassing (15–20 minutes) is required. An online degasser serves only as a supplementary measure and cannot replace ultrasonic degassing. Buffer salt solutions must be used within 24 hours; any unused portion should be refrigerated and brought back to room temperature with re-filtration before the next use.
Stable pressure is critical. When mobile phase composition and flow rate remain unchanged, column pressure should stay stable. A sudden pressure increase typically indicates column blockage or degradation; a sudden pressure drop should first prompt a check for leaks at connections, followed by a check for air bubbles inside the pump.
Correct bubble removal sequence: STOP pump → Open purge valve → Press PURGE for rapid flushing → Stop pump after bubbles are expelled → Tighten purge valve. Do not reverse the sequence.
This is the most easily overlooked yet most critical step, directly determining the service life of the pump and column.
Mobile phases containing salts/acids: After the run, the system must be flushed with 95% double-distilled water and 5% methanol for 40 minutes, followed by pure methanol for 30 minutes, to prevent salt crystallization from corroding the system. Never shut down overnight with buffer salts remaining in the system — salt crystals will wear down pump seals and block lines. Before use the next day, transition with water-methanol in the same ratio for 20 minutes.
Pure organic mobile phases: After the run, flush with pure methanol for 30 minutes before shutdown.
Only after the complete flushing procedure should the instrument be turned off. Never cut power directly after a run. Shutdown sequence: Press STOP to stop the pump first, then turn off the power.
Columns are consumables with high procurement costs; proper daily protection can significantly extend their service life.
Install a guard column: Where conditions permit, install a guard column upstream of the analytical column to trap sample impurities and protect the analytical column.
pH range: Strictly adhere to the column's pH tolerance range (typically pH 3–8); do not exceed the specified limits.
Storage method: For commonly used reversed-phase columns such as C18, high proportions of methanol or acetonitrile are recommended for long-term storage. Do not store reversed-phase columns in pure water for extended periods. For short-term storage (1–7 days), after flushing, seal the column with its original end caps to prevent air from entering and drying out the packing.
Usage log: Keep a simple record of each column's usage history and sample types analyzed.
II. Systematic Periodic Deep Maintenance (Weekly/Monthly/Quarterly)
In addition to routine daily maintenance, a systematic periodic deep maintenance schedule should be established. Based on usage frequency and runtime, targeted maintenance should be performed on core components including the pump head, injection system, detector, and filtration devices — reducing failure rates at the source and ensuring long-term precision operation.
Weekly maintenance should focus on the injection system, suitable for a typical throughput of approximately 200 injections per week. Use a lint‑free cotton swab moistened with purified water or methanol to gently wipe the injection port and sample loop, removing residual sample impurities to prevent cross-contamination and injection jamming. Replace the rotor seal regularly according to usage frequency to prevent leakage and injection precision degradation due to poor sealing, ensuring injection repeatability and stability.
Monthly maintenance should cover a comprehensive inspection of the pump head, seals, and filtration devices, suitable for approximately 500 hours of operation. Flush the pump head and wash valve with a 1:1 mixture of purified water and methanol to remove residual impurities. Regularly inspect and replace piston seals; if pump head leakage or frequent pressure fluctuations are observed, immediate inspection and seal replacement are required to prevent minor issues from escalating. Simultaneously, maintain the mobile phase suction filter and inline filter elements. Place the suction filter in a beaker and ultrasonicate sequentially in purified water and methanol for 10 minutes each. If severe clogging occurs, soak in 20% nitric acid for 1 hour, then rinse thoroughly with water and methanol. Replace inline filter elements regularly to ensure effective mobile phase filtration and prevent impurities from entering the fluid path.
Quarterly maintenance should focus on cleaning the detector flow cell. This can be performed earlier if baseline noise or baseline drift increases. Follow a standardized cleaning procedure: sequentially flush the flow cell in reverse with purified water, 0.1 mol/L nitric acid, purified water, and methanol. Strictly control the flow direction to avoid damaging optical lenses. Hydrochloric acid is strictly prohibited as it can corrode precision optical components. After cleaning, baseline noise should be reduced and detector sensitivity restored.
In addition, every 15 days, add 2–3 drops of specified lubricating oil to the pump’s oil injection port to lubricate transmission components, reduce mechanical wear, and extend pump life. After each mobile phase change, thoroughly purge and flush the lines to eliminate solvent stratification and residual bubbles. It is also strongly recommended to establish a dedicated instrument maintenance log, recording startup/shutdown times, sample throughput, column pressure variations, abnormalities, maintenance dates and actions — enabling traceable equipment management, accurate prediction of component wear, and proactive failure prevention.
III. Specialized Maintenance for Long‑Term Idle Equipment
When laboratory instruments are idle for extended periods, issues such as microbial growth in lines, check valve sticking, solvent evaporation and contamination, and line blockages can easily develop. Specific preservation maintenance is required.
For short‑term idling: Thoroughly flush buffer salts and acid/alkaline residues from the lines and column with purified water, then seal the entire fluid path and column with pure methanol.
For long‑term idling: Immerse the filter head in methanol and seal it. Start up the instrument every two weeks and circulate the system for a period to prevent component sticking. If poor fluid uptake or pressure anomalies occur upon startup, use the PURGE rapid‑flush function to remove air and clear blockages, ensuring the instrument can quickly return to stable operation when brought back into service.
Following the above operational practices and maintenance schedule will significantly reduce HPLC failure rates, ensure long‑term stability and reliability of analytical data, and is applicable to various analytical fields including pharmaceuticals, chemicals, and food testing.
Frequently Asked Questions (FAQ)
Q1: How should the HPLC system be properly stored and maintained when not in use for extended periods?
A: For short‑term idling, thoroughly flush buffer salts from the lines and column with purified water, then seal the system and column with pure methanol. For long‑term idling, start up the system periodically to flush it and prevent microbial growth in lines and check valve sticking; seal mobile phase bottles to prevent solvent evaporation and contamination.
Q2: What are the most likely causes of high column pressure during daily use?
A: High pressure is often caused by buffer salt precipitation, line blockages, a dirty inlet frit, or column packing blockage. First inspect the lines and frit, then flush the column with purified water and methanol at low flow rates sequentially. Do not flush at high flow rates or pressures, as this can damage column efficiency.
Q3: Can the mobile phase be left in the lines after each run?
A: Not recommended. Mobile phases containing buffer salts, acids, or bases should never be left in the lines for extended periods, as they readily crystallize and block the pump, check valves, and lines. After each run, salts must be thoroughly rinsed out with purified water, and the system sealed with organic phase to protect pump and seal life.
Conclusion
The stable operation and extended service life of high-performance liquid chromatography (HPLC) systems hinge on three core principles: prevention-focused mindset, meticulous maintenance, and standardized operations. A trinity maintenance system comprising routine standardized operations, periodic deep maintenance, and specialized care for idle periods effectively resolves common issues such as baseline instability, pressure anomalies, peak distortion, and poor data reproducibility, while significantly reducing equipment failure rates and operational costs. For demanding applications such as pharmaceutical GMP testing, food regulatory inspection, environmental monitoring, and precision research experiments, standardized maintenance not only serves as the foundation of equipment care but also provides the critical assurance that analytical data are accurate and reliable, and that experimental results remain compliant and valid. Adherence to consistent, regularized maintenance maximizes the analytical performance of the HPLC system, extends the service life of both the instrument and columns, and establishes a solid foundation for efficient, stable, and compliant laboratory testing operations.
