Hi !

I am a Danish technician who's having a disccusion with my chemist about fingertight fittings to HPLC columns. I've been taught that these fittings ar almost universal to every HPLC column on the market, but my chemist is not agreeing. Could somebody help me with this matter, and give me some proof that fingerthight fittings can be used ??
In this way live would be a little more bearable for me and my co-workers.

In general, fingertight fittings are universal, because they do not permanently crimp onto the HPLC tubing like metal nut/ferrules do and reshape to the internal surface of the column end fittings to provide a good seal.

We find that if you use them with PEEK tubing, they can cause more problems than with stainless steel tubing because some degree of crimping does occur, although it is still possible to move the fitting.

The only issue is ensuring the tubing is properly seated in the column end fitting and that it is sufficiently tightened. If done correctly, most fingertight fittings are rated to 5000psi, which is well above the generally accepted maximum column pressures.

I agree with Tim. I have found fingertight fittings to be excellent with Stainless steel, but not as good with PEEK tubing. We have experienced some minor problems with leakage under elevated pressures (2500-3500 psi). We have also seen the crimping effect on the PEEK tubing. As for your proof - what exactly are you looking for - perhaps someone from Upchurch could give you the answer you want.

Upchurch is a very good choice for fittings! Go to their Web side at www.upchurch.com and order their free booklet on HPLC fittings. They carry the three most common used sizes of threads: Parker (used by waters)us customary and metric.

Upchurch and Optimize make very good fittings for what you need, although it is my experience that the Upchurch fittings last longer, while Optimize makes for the best (i.e. non-leaking) connection.

Thanks for your reaktions ! It's good to find out that I'm not alone!

Well, about my proof. My chemist won't accept proof from manufacturers, because he thinks that they say that their fittings are universal, just to sell more. In this matter he might be right, but where else to find some proof ???
Now, with your messages I might have a better point ! But if anyone knows about some proof please add a message !! I'll be checking this site !

Basically, finger tight fittings are universal because when you remove the fitting from the first column, the ferrule can still be moved up and down the tubing, adjusting to fitting of a different column. In general, because I am always changing plumbing configurations on my LC, I avoid stainless steel as much as I can. Also, because I use different brands of columns, I never use stainless steel fittings. I would never be able to make up a good connection. Void volume in one connection; ferrule too far up for another connection.

What kind of proof is your chemist looking for?

I don't precisely know what proof my chemist i looking for, but I want to have some kind of statement that he can't ignore.
He just won't believe me and my co-workers, or producers of these kind of fittings. He needs to be confronted with some kind of statement from a third party with some reputation, I think.

OK, then, I'll bite. I think the situation with respect to plastic fittings is very well covered by the posts in this thread. So long as you get the right thread pitch for your column end and are careful about overtightening, the fittings work well across a wide range of columns.

I don't know if my reputation will carry any weight with your chemist (it carried almost none with my children when they were teenagers!), but I have been doing chromatography for > 30 years. Over the past decade, I have taught practical HPLC, method development, and troubleshooting courses to over 2,000 chromatographers.

Trust me! ;}

-- Tom Jupille / LC Resources

Thanks mr. Jupille. This was the answer I was waiting and hoping for !
Now what left for me is talking it all over and come with all the arguments I've been getting here.
This forum i a great medium for those questions !
Thanks again.

:-)

Holger

My pleasure (and good luck!)

-- Tom Jupille / LC Resources