The high performance liquid chromatography is a valuable asset in the laboratory – expensive to purchase and critical to operations. A well‑maintained HPLC system not only ensures accurate and reliable experimental data but also significantly extends its service life, saving you considerable maintenance and consumable costs. Today, we will provide a detailed breakdown of daily HPLC maintenance tasks and essential precautions that must be kept in mind.
I. Daily Maintenance Tasks (Good Habits Are the Foundation)
Taking just a few minutes each day to do these tasks will prevent most unexpected failures.
Mobile Phase: The Source Determines Success
Water purity: Always use HPLC‑grade or ultrapure water. Ordinary deionised water is unacceptable.
Filtration: All mobile phases, including both aqueous and organic phases, must be filtered through a 0.45 μm or finer 0.22 μm membrane before use. This is the first line of defence against system blockage.
Degassing: Mobile phases must be degassed before use to remove dissolved gases, preventing bubbles from forming in the pump and detector that would cause pressure instability and baseline fluctuations. Sonication is simple and commonly used, but an online degasser delivers better results.
Pump System: Maintaining the Heart
Final flush: After each experiment, if a buffer salt or salt‑containing mobile phase has been used, first flush the column with 10 % methanol/water for 30 minutes to ensure complete removal of ionic residues, then flush with a high‑proportion organic phase (e.g., 90 % methanol or acetonitrile) for another 30 minutes. Do not flush with pure water, as this may cause column packing collapse and damage. Before use the next day, equilibrate with the same water‑methanol ratio for 20 minutes. This step effectively prevents salt crystallisation and microbial growth, and is the secret to long pump and column life.
Start‑up equilibration: After starting up, equilibrate the system with the initial mobile phase at a moderate flow rate for 10‑15 minutes to allow pressure and baseline to stabilise before beginning formal experiments.
Autosampler: Details Make the Difference
Clean needle: After each experiment, flush the injection needle and its exterior multiple times with pure methanol or acetonitrile to prevent cross‑contamination or crystallisation that could clog the needle.
Replace septa promptly: The injection port septum is a consumable item. Replace it when a certain number of injections has been reached or when the septum shows signs of fraying, to avoid leakage.
Column: Protecting the Core
Install a guard column: Installing a small guard column in front of the analytical column is low in cost but acts like a “shield”, intercepting strongly retained impurities and particulates, greatly extending the life of the expensive analytical column.
Proper storage: After flushing the column according to the procedure, always seal both ends tightly with plugs to prevent the bed from drying out. For long‑term storage, the column should be kept in pure organic solvent (e.g., methanol).
II. Regular In‑Depth Maintenance (Prevention is Better than Cure)
Beyond daily tasks, regular in‑depth maintenance is essential.
Weekly check: Inspect the pump head for signs of leakage. Check the colour of the in‑line filter; if it has darkened, remove and clean or replace the frit.
Monthly maintenance: Depending on usage frequency and the strength of buffer salts, plan to replace pump seals periodically (e.g., every 3‑6 months). Record deuterium lamp usage hours; when approaching the rated lifetime (typically 1000‑2000 hours), watch for baseline changes and prepare a spare lamp in advance.
As‑needed maintenance: When detector baseline noise increases significantly, it may indicate a dirty flow cell or trapped bubbles. Refer to the instrument manual for cleaning and purging the flow cell.
III. Essential Precautions (Avoid These Pitfalls)
Buffer Salts Require Special Attention
Critical warning: Never leave buffer‑containing mobile phase in the instrument overnight, especially over weekends. Salt crystallisation can severely damage the piston and seals, causing permanent harm.
Prevent precipitation: Mixing buffer salt solutions with high‑proportion organic phases can cause precipitation. When changing mobile phase ratios, transition smoothly to avoid abrupt changes.
Follow the Correct Operating Sequence
Start‑up sequence: Turn on the online degasser and detector first, then start the pump, and finally open the workstation software, allowing the system pressure to rise smoothly.
Shutdown sequence: First stop data acquisition, then thoroughly flush the system as described in the “final flush” procedure, then turn off the pump and detector, and finally close the software and power.
Safety and Environmental Protection Must Not Be Overlooked
When handling toxic solvents, always work in a fume hood and wear appropriate gloves and goggles.
Waste solvents should be collected separately and disposed of by authorised agencies – protecting the environment also protects ourselves.
Maintain a Log
Keep an instrument usage and maintenance log, recording start‑up status, samples run, any abnormalities, and parts replaced (e.g., deuterium lamp, seals). This log will become your best assistant when troubleshooting in the future.
In summary, HPLC maintenance is not complicated. The key lies in maintaining good daily habits and remaining vigilant about buffer salts. Treat the instrument as your partner, care for it diligently, and it will reward you with stable and reliable data.
Frequently Asked Questions about HPLC Maintenance
Q1: What could cause a sudden high pump pressure after start‑up, and how should it be handled?
A: Common causes include: blocked tubing due to insufficient mobile phase filtration, column or guard column contamination, or faulty check valves. Troubleshooting: First check the in‑line filter; if dirty, clean or replace the frit. If the filter is normal, disconnect the column and connect a union; if pressure returns to normal, flush or replace the column/guard column. If the problem persists, remove and clean the check valves.
Q2: If the baseline continues to fluctuate (high noise) after bubble issues have been ruled out, what else can be done?
A: Possible causes include: an ageing deuterium lamp (check the usage hours), a contaminated flow cell, or detector circuit problems. Troubleshooting: First try a new deuterium lamp. If that does not help, flush the flow cell with methanol‑water (1:1). If the problem persists, contact a service engineer to inspect the detector circuit.
Q3: No chromatographic peaks appear after injection. Where should I start troubleshooting?
A: Follow these three steps:
Injection system: Check whether the needle is blocked and whether the injection port septum is leaking. Ensure the sample is being properly introduced.
Column: Confirm that the column is compatible with the mobile phase. If column efficiency is too low, replace the column.
Detector: Check that the detector is turned on and that the signal is being transmitted properly. Restart the detector and workstation to see if communication is restored.
