When a liquid chromatograph leaks during an experiment, it not only delays progress but can also affect data quality. However, once you master the methods, you can quickly resolve the problem. First, let’s understand the basic structure of a liquid chromatograph: it mainly consists of a solvent reservoir, pump, injector, column, detector, and recorder. The mobile phase from the reservoir enters the system through the high‑pressure pump, and the sample, carried by the mobile phase, enters the column. Because different components have different frequencies of “adsorption‑desorption” on the stationary phase and mobile phase, they gradually separate, then pass through the detector where they are converted into electrical signals, and the results are output as a chromatogram.
Leakage is a common problem encountered during daily use of the instrument, especially leakage from the pump – the “hardest hit area”. Today we will discuss the common locations of pump leakage and their solutions.
I. Leakage at Fittings and Tubing
Often, leakage is not caused by a broken part, but by a loose fitting or a sudden increase in system pressure that has loosened the connection. Therefore, when you first observe a leak, don’t rush to replace parts. In most cases, simply tightening the fitting will solve the problem. If the threads are stripped, replace the fitting.
II. Leakage from the Pump Head
Leakage from the pump head is mainly due to two reasons:
Worn seal
With long‑term use or frequent exposure to corrosive liquids, the pump head seal gradually thins. Once a leak occurs, it means the seal needs to be replaced. After installing a new seal, the pump will return to normal operation.
Faulty check valve
A clogged check valve can cause abnormally high system pressure, which then leads to leakage. In this case, remove the check valve, immerse it in a 10% methanol/water solution, and sonicate for 10 minutes. After cleaning, reinstall it and test. If leakage persists after cleaning, replace the check valve.
III. Daily Use Precautions for Liquid Chromatographs
Regularly inspect consumable parts
Before turning on the instrument each week, check the pump fittings, tubing, and pump head seal for any signs of liquid residue or deformation. Catching small problems early can prevent the leak from worsening.
Follow proper operating practices
Do not overtighten the check valve when installing – just tighten it enough so it does not wobble, to avoid stripping the threads. When changing mobile phases, remember to filter and degas the solvent; bubbles can cause pressure fluctuations and indirectly increase the risk of leakage.
Take safety precautions
Always wear gloves when dealing with leaks (especially corrosive mobile phases). If liquid spills on the bench, wipe it up promptly with absorbent paper to prevent liquid from seeping into the instrument and damaging components.
Keep maintenance records
After replacing a seal or cleaning a check valve, simply record the operator’s name and the date. The next time a similar problem occurs, you can quickly trace back and also better judge the replacement cycle of parts.
IV. Maintenance Tips for the Pump and the Whole Instrument
Periodically flush the mobile phase tubing
Every time you change to a different type of mobile phase (e.g., from aqueous to organic), or after finishing an experiment, flush the tubing with pure methanol or acetonitrile for 15‑20 minutes to prevent residual liquid from crystallising, blocking the channels, or corroding the tubing walls.
Lubricate pump head moving parts
Once a month, apply a small amount of special grease (do not use ordinary machine oil) to the moving parts of the pump, such as the plunger rod. This reduces friction and wear, extending the service life of the seals and the pump head.
Control the instrument environment
Place the instrument in a well‑ventilated, dry area, away from sinks or air conditioner outlets. Humid conditions can cause electrical components to become damp, and sudden temperature changes may cause fittings to contract and leak.
Maintenance when not in use for a long time
If the instrument will not be used for more than a week, first empty the mobile phase from the tubing, then flush with pure methanol before shutting it down. Before restarting, circulate methanol for 5 minutes before changing to the actual mobile phase, to prevent bacterial growth or precipitation inside the tubing.
