Chromatography Forum

Hi folks,

I'm installing a new column in my HPLC and it indicates that a Parker end-fitting is required.. Since I have never had to do this.. I am confused.. I have looked at Agilent, VWR and Upchurch, but no one seems to have Parker end-fittings.. am I missing something.... What is so special about the Parker end-fittings and many of the others out there.. seems like there is more than a handfull of fitting kinds available...

I would appreciate any help and comments..

Thanks in advance

- Hubert

Hubert,

The only reason to specify a specific end fitting manufacturer is connected to ferrule placement and ferrule shape. The exact positioning of relative to an already swaged ferrule is dependent on the end fitting design so if you want to replace an existing end fitting you generally need to replace it with an identical component. If you don't have any Parker fittings handy, you may be able to get away with an alternative supplier but be aware that you may either observe a leaking problem is to ferrule placement is too far back or a dead volume problem with an associated efficiency loss if the ferrule is too far forward.

Hi Chris,

Thanks for the info.. quick question.. are all of the ferulles similar.. If I use a NON-swage tube, and insert into the fitting this should allow me to eleviate this issue.. right?? When I insert the SS tubing into the fiitting till it tops-out, that should get rid of the dead volume issue.. right?

Thanks again for all your help..

- Hubert

Hubert,

I have never heard of this requirement before. The Parker ferrules are two-piece and were standard for gas chromatography fittings. They were actually used in the early days of HPLC but have been replaced by the one-piece ferrules that are now commonly used. My experience has been that the cone-shaped one-piece ferrule from any of the vendors will work in any current column. The only different style of ferrule to watch out for is the SSI which is shaped like a hat and is specific for SSI fittings. Be sure that you insert the tubing into the column as far as it will go and tighten the ferrule to get a leak-free seal. Don't overtighten! You can always tighten a little more if the seal leaks.

If I understand Hubert correctly, he is using a PEEK ferrule. These things are much better than steel ferrules, since they can be positioned into the column such that there is no dead volume, no matter what the specific design of the seat for ferrule and tubing is. The only disadvantages about the PEEK ferrules are that they also can slip, and they wear faster than a steel ferrule.

If you have a steel ferrule installed that is too short for the seat, you will have dead volume in your column top and you will not get the plate count that you could get from your column. Unfortunately such a thing is quite common, and many people don't even realize that there could be a problem. They just think that the column is not as good as the manufacturer claimed. These column manufacturers are lying anyway, don't they?

Hubert,

Sorry, I misunderstood your original post. As long as you are using PEEK ferrules, there shouldn't be any problem using columns with different end fittings in spite of the instructions you noted. The only requirement is that you make sure the ferrule is properly seated. Depending on the ferrule design, this may or may not be an easy matter. The way to make sure that the ferrule is seated properly is to slide it back, say, 5 mm and tighten the tube fitting until snug (which will slide the ferrule back into the right place) while holding the tube against the column end fitting (I know this sounds like it requires three hands but it can be done with a bit of experience with out assistance from another person). If you are going to be using a stainless steel fitting, stainless steel tubing and stainless steel ferrule you should not use tubes prepared for use with one type of end fitting with another type of end fitting as there is a significant risk that the ferrule will be swaged in the wrong place (resulting in either a leakage problem or a dead volume problem depending upon where the ferrule is relative to the proper location on the connecting tube).

skunked_once

Actually, the standard Parker ferrule is a one-piece design although I think you can also buy a two-piece design if you special order it. It's Swagelok that uses the two-piece ferrule design (Parker and Valco were forced to use a one-piece design because Swagelok had a patent on the two-piece design although this patent has since expired).

Hi Folks,

Thanks again for the answers.. this is very helpfull.. I am planning on using the PEEK fittings with SS tubes from Agilent. Since my column is not designed for swage, I have to go this way.. and in the end it is much better, as I want to have the felxibility to change columns fairly often, and this will allow me to do so.. if the fitting wears out.. I'll just replace it..

Thanks again for all the help..

- Hubert

Re: Agilent SS tubing & peek ferrules - I have had to grab a file and slightly "rough up" the outer surface of Agilent tubing on the column compartments of several 1100s to keep peek ferrules from slipping on them (at anything >150bar). Evidently, the "fat" ends of the microbore tubing sections they use are highly polished and are, therefore, more prone to slipping than most standard SS tubing is. All you have to do is slightly scratch the surface in a few places 1-3mm from the end and they work fine.

Hi DR.

Thanks for the info, I will not be running anywehere close to 150 bar (usually around 66 bar), but will scratch up the surfaces a little to make sure I get some good connections.

Thanks again for the help..

- Hubert

The HP/Agilents come with swaged SS fittings (or used to) so when we replace them we put fingertight fittings on the column ends of the capillaries.

Upchurch´s Lite-Touch (PEEK with a steel ring) should not "slip" at normal HPLC pressures (400 bar). In this lab we have had no problems up to our max. of 250 bar (1/16 as well as 1/8") for years as long as they are not squashed. If needed one can move these also, a bit difficult sometimes, but possible. Another advantage of plastic ferrules is that you can get a tight fit even in fittings (the concave side) which have been ruined by steel ferrules

The biggest difference in ferrule position encountered here is between old and newer Rheodynes (7125, 8125). The nut of a tubing swaged for the older one doesn´t even "catch" the threat of a newer one.

On the other hand, you may get a Waters swaged fitting into a seat requiring a shorter tube protrusion: bad news!