expected life/temp limits of methyl-deactivated cap. tubing

[jf]

we are currently using a metal column on our GC for better hi-temp stability (our method tops out at 380C for 10 mins.) our baseline rose relatively quickly with the fused silica column.

i have a question with regard to the methyl-deactivated capillary tubing we are using as a guard column. This is also metal tubing, as per varian recommendation.

It appears that methyl-deactivated fused silica is quite a bit more cost-effective, but i am concerned about its ultimate life at this temperature.

I guess what i'm getting at, is that since the tubing is deactivated, will the breakdown that normally occurs at high temperature with fused silica actually affect our results if its only used as a guard?

thanks in advance!

[Peter Apps]

The upper temperature limit for fused silica tubing is set by the polyimide coating on the outside, not the stationary phase and deactivation on the inside. Metal columns last longer at high temperatures because they do not need a polyimide coating to protect them. Deterioration of the polyimide cannot affect the detector signal, until the silica column actually breaks.

Peter

[chromatographer1]

Your samples will determine the lifetime of the guard column or retention gap.

The presence of water and other impurities will initiate the activation of the 0.53mm ID column.

Also the presence of air (oxygen) can cause problems.

best wishes,

Rod