hi,
i am looking for a good coupler/connector to connect 2 GC capillaries together, at first i thought to buy union from VWR/Valco, based from my experiences with capillary LC, then i was told by the GC column vendor that those type of connector has too big void volume for GC, so they send me a few pieces of tubing from their own supply, which is not available from the market. it works. the only problem is now the retention time increase 4 times, as supposed 2 times because of the doubled length, so i think the leaking from the tubing part may be the problem, the tubing is kind of teflon material with the right size id to fit the capillary, the best i can do is just use my fingers to push the capillary into it as far as not too hard to break it inside the tubing(this happened first time when i tried), so there is no way i can guarantee it's not leaking.
so please anyone know a better connector for air-tight connection for capillary GC?

thanks.

There are various glass press fit and ferrule connectors availalbe from all the major column supply companies. I am surprised that any type of polymeric tubing would work at all if you are doing temperature programming.

no,
i am only doing isothermal. can you tell me the name of which company has the right connector?

metal compression housing butt connector $38.50 ea
p270 Supelco Catalog 2003/4
Catalog number 23796 (for 0.25mmID columns)
choose your ferrule from table
for other column IDs

Glasseal connector pk of 12 $58/pk
catalog 20479

Other companies have similar offerings. All can do an excellent job. Take your pick

Perhaps all is OK.
If you couple two columns the flow rate is halved and thus for twice the length the isothermal elution time should be 4 times longer
Aviv