Get Connected!
Have you ever had to connect a GC analytical column to a guard column or transfer line? Or repair a broken column? How about connecting two columns in series or performing confirmation analysis with a single injection? All of these connections are possible with Restek’s extensive selection of GC connectors. In most situations, connector choice is a personal preference and Restek offers several options. Here we review differences among our connectors and answer some frequently asked questions about our popular Press-Tight® connectors.
The Press-Tight® connector, a glass connector with a tapered internal diameter at each end, is the quickest and least expensive option. Straight or angled Press-Tight® connectors are effective for fused silica-to-fused silica connections for standard applications at temperatures below 325°C. The resulting connections are inert and have low dead volume.
The MXT™-Union connectors are unbreakable metal connectors that are reusable and ensure a low dead volume. They are designed for metal-to-metal connections, but also can make metal-to-fused silica unions using a Valcon polyimide adaptor. This unique graphite-reinforced composite allows a capillary column to slide into the adaptor and be locked in place simply by loosening and tightening the nuts.
If you require a fused silica-to-fused silica connector for high temperature applications, try Restek’s Vu2 Union™ connector or SeCure™ “Y”connector. They combine the simplicity of a glass connector with the strength of a metal connector. Both connectors feature an open design that allows visual confirmation of the seal, and also have secondary seals to help maintain a leak-tight connection. These ultra-strong connections will not disconnect unexpectedly under temperature changes, vibrations, or other stresses normally encountered in GC analysis.
Restek also offers a Vacuum Vu-Union® connector for connecting a fused silica column to a mass spec transfer line. The Vacuum Vu-Union® connector utilizes Vespel® ferrules for nonpermeable vacuum connections. A specifically designed Vu-Union® glass insert permits more torque to be applied to the ferrules without fear of cracking the insert. As with the Vu2 Union™, you can confirm the seal through the window of the connector.
What is the difference between angled and regular Press-Tight® connectors?
The only difference between these connectors is their shape. A Press-Tight® connector is a straight tube; an angled Press-Tight® connector has a slight angle in the middle which reduces the strain on the fused silica tubing. This is of particular use in making a connection in a broken column, when you must make the connection within the column coils.
How can I obtain a leak-tight seal using a Press-Tight® connector?
Press-Tight® connectors are easy to use, but if they are not properly sealed, they can loosen due to thermal expansion during temperature-programmed runs. The keys to successful sealing are:
1) making a clean, square cut on the column and 2) moistening the end of the column with methanol before seating it into the connector. A small amount of polyimide resin also helps prevent the seal from separating during temperature cycling.
Can Press-Tight® connectors be used with MXT® columns?
No. To achieve a leak-tight metal-to-metal connection, we recommend the MXT™ Low Dead Volume connector for metal columns. These low dead volume connectors are Siltek® treated to make them inert to active compounds, and they can be used up to 400°C without degrading the deactivation layer. MXT™ tubing can even be connected to fused silica tubing using an MXT™ connector with a Valcon Polyimide ferrule instead of a stainless steel ferrule.