Chromatography Forum

I have been reading multiple sources that say PEEK tubing is one preferred methods of connecting components used in HPLC analysis. I have PEEK tubing and connectors purchased form www.chromspec.com (part numbers on their site are RK25066 and RK25015 respectfully) and I have had no luck with them, the pressure builds and the tubing pops out.

It may be the case that I have the wrong size tubing, but literature tells me that PEEK connectors should be able to hold PEEK tubing with pressure up to 400 bar. I have tried using PEEK tubing and connectors and have never had success above 150 bar.

I'm wondering if anyone has had similar issues? I'm currently using stainless steel connectors and tubing but they are getting older and leak (very small leak) occasionally. I can buy new stainless materials, but I hate to see the PEEK go to waste if there is some way I can make it work.

What kind of ferrules are you using? Personally, I've found that the fingertight nuts with separate PEEK ferrules hold higher pressures tha the one piece fingertights, but that was years ago and I haven't tried more-recent one pieces.

I have been reading multiple sources that say PEEK tubing is one preferred methods of connecting components used in HPLC analysis. It may be the case that I have the wrong size tubing, but literature tells me that PEEK connectors should be able to hold PEEK tubing with pressure up to 400 bar. I have tried using PEEK tubing and connectors and have never had success above 150 bar.

I also had the same problem with PEEK ferrules and fittings. Well designed ferrules, like the ones used in Dionex systems, can easily hold up to 3000 psi (~ 200 bar). These are compression type fittings in the sense that the ferrule actually compresses the PEEK tubing and stays locked there.

Stainless tubings also work, but require the skill of proper tightening otherwise, in few uses, the screw and the ferrules become useless and leak. If you are willing to spend money, Nanoviper tubing might wipe your tears once for all. They are finger-tight, and easily tolerate very high pressures (1000 bar) without leaking. The only incompatibility is with the normal phase when the tubings can burst because of mobile phase compression effects.

Also for Peek tubing it is a must to have a proper cut of the tubing and when you seal it never do body building. Finger tight means tight with fingers.
Most important is that the Peek tubing is compatible with the mobile phase. And from time to time use a new tubing.

I never trust "one-piece" finger tight fittings. I only use ones with separate nut and ferrule. The three-piece fittings with nut, ferrule, and metal collar will bite down on the tubing like stainless steel fittings. Those are reliable in my experience.

Cleaning the capillary end with e.g. acetone will remove any lubricating material. This emproves the pressure staility of the PEEk connectons quite a bit.