Solution method of liquid chromatography pipeline joint failure

Abstract: Blockage is the main fault of the pipeline. If the pipeline is completely blocked, the pressure will suddenly rise and overpressure. Partial blockage is not obvious at the beginning, and the pressure of the particles that are constantly in the liquid flow will slowly increase, and finally block completely. When the pipeline is blocked, you will see the joint or gasket leaking. The low pressure is better, and the high pressure leakage is obvious.

1. The pipeline is blocked

The complete or partial blockage of the pipeline is caused by the following reasons: â‘  the mobile phase is not well filtered; â‘¡ there are particles in the sample; â‘¢ fragments are generated in the pump or sampler gasket; â‘£ packing is leaked from the pre-column, guard column and analytical column; â‘¤ Burr and filings entered; â‘¥ Crystalline salt in the mobile phase; â‘¦ Microorganism â‘§ Other particulate matter entered the system.

The blockage of the pipeline in the system is rare, and the common one is the blockage of the sintered filter (glass sand core). Using sintered filter or filter (pore size 2-10um) can remove the particles blocking the pipeline (such as 0.25mm pipe diameter). Use the system segmentation method to check the blocked pipeline, and then loosen the joint inspection from the back to the front. Once the blocked pipeline is found, it should be removed immediately to dredge or replace it.

If it is blocked by non-rigid substances, such as biochemical substances (proteins) and microorganisms in biological samples, they can be turned on with very thin metal wires, or they can be burned on the fire head to carbonize the organic matter and then turned on.

If it is blocked by a rigid substance, it is very difficult to conduct, and the method of recoil can sometimes succeed. It is to flush the pipe with a pump. Care should be taken to protect eyes and bare skin during operation, because the obstruction will rush out at a high speed. Replace the pipes with the same specifications if they cannot be connected. If it is blocked after changing to a new tube, it should be shut down to check the above mentioned causes of the blockage.

2. The pipe head is damaged

Uneven pipe cuts or sealing sleeves cannot be sealed. Re-cut the broken pipe head (including the ferrule), replace the new ferrule, install the joint and squeeze and tighten. Most leaks are caused by joints, not pipe problems.

3. Prevention and solution of joint failures Almost all joint failures can be avoided, and joint failures can be effectively prevented according to the following requirements:

â‘  Parts used when designing the instrument (such as parts from the same manufacturer);

â‘¡Use good joint parts (such as zero dead volume, ie V0 = 0 when the sample passes);

â‘¢Assemble and tighten the joints as required, and do not overtighten;

â‘£ Avoid confusing the use of connectors, make a timely mark;

â‘¤ Use qualified tools. When assembling / disassembling the joint, check for particles and inorganic salt crystals on the sealing surface. These contaminants affect the sealing performance and make the screw bite more seriously. Finally, it is best to use a dead wrench when tightening the joint to ensure that the joint is not bitten. Usually prepare some spare parts of various joints that can be used.

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