Column coupling remains a very interesting topic. Whether its for connecting a guard column, a retention gap, column extension, transfer line s to one or multiple detection systems, or just repairing a broken column. For fused silica coupling the PressTight has found wide application. For ease-of-use the universal PressTight was developed.
http://www.restek.com/catalog/view/370
To enhance response and peak symmetry these PressFits are also deactivated. The difference is best seen when looking at the peak shape of a polar component, like hexane diol see fig.1. Besides the standard siloxane deactivations, Restek also offers a Siltek deactivation which shows remarkable inertness for sulfur and organo-metal type compounds.
Making the connection si not always easy. We get complete opposite reactions varying from customers that cannot make a leak tight seal at all to people that make hundreds of seals using mass spectrometry, and never have a leak.
When making a connection with fused silica its important to cut a 90 degree cut. This can be done with wafer, a diamond needle pen or even a “shortix” cutter. Pushing that end in to the Presstight with a little force will give you already a seal. You can see the seal by the formation of a brown-ring all around the top of the column. Better is to wipe the outside polyimide after cutting with some solvent (methanol, acetone) and then make the connection. Fig 2 shows the difference. Using a solvent wipe, we remove finger fats and it will make the contact surface a little larger which will result a better and more durable seal.
This sealing area is important as we always damage the poly-imide a little when we use the cutting tools, see fig 3. The more sealing-surface we have in thw connector, the more chance we have to maintain a good seal.

Fig 2 Wiping the fused silica end will remove fats and will make a larger contact surface resulting in a better seal
To reduce the stress on the press tights there are also PressTights with an angle, http://www.restek.com/catalog/view/366
or one can choose for the VU2 union where the ends are secured by an extra connection, see http://www.restek.com/catalog/view/4689
Alternate one can use some polyimide to secure that the ends of the column do not slip out easily. It more messy, than a VU2 union, but it also works, see: http://www.restek.com/catalog/view/325
The maximum temperature for PressTight type connections is about 330C. Above that we see often appearance of leaks due to hardening of the polyimide outside coating.